04-17-01 16:24
No 184808
Here's my idea: Add about 200g Na/K bromide to a 500ml flask, rig a 250ml sep funnel to the flask, which contains H2SO4. Have a tube leading from the flask to a large raft, and make sure everything's air-tight. Drip the H2SO4 into the flask and fill the raft with the HBr. Add a shit-load of safrole to another 500ml flask and add just enough acetic acid to dissolve the safrole. Put the flask in NaCl/ice, rig the raft up to it. Then put a 20 pound weight on top of the raft, which will speed-up the saturation of HBr. Let it be for about 2 days, let the acetic acid evaporate and you'll be left with a mean chunk of bromosafrole! My concern: Would anhydrous HBr eat through a rubber raft? Peace!
I'm going to help all of you cleanse this diseased planet.
(Hive Bee)
04-17-01 20:45
No 184852
Im confused. The raft does what now? where does it go in relation to the other stuff? And what is a raft?
marijuana is the flame, heroin is the fuse, LSD is the bomb!
(Hive Bee)
04-18-01 00:35
No 184901
"And what is a raft?"
I'm going to help all of you cleanse this diseased planet.
(Hive Addict)
04-18-01 02:40
No 184915
Why not pipe the HBr right into the safrole as its being made?
Do Your Part To Win The War
(Hive Bee)
04-18-01 09:41
No 185020
pipe the gas into a large hard plastic container(like a gas can) instead of a raft. then pump a non polar solvent into the container to displace the gas and pressurize it. I doubt that a raft would take but about 2atm of pressure to burst, and that cloud would do a number to your lungs and skin.
If pacman influenced us, we'd glide around dark rooms eating pills and listen to repetitive music.
(Hive Bee)
04-18-01 21:48
No 185183
"Why not pipe the HBr right into the safrole as its being made?"
I'm impatient - it takes too long to bubble HBr into safrole/acetic acid, so I figure that hooking-up an HBr-filled raft and putting weight on it will get the job done. The concentration of HBr definately would be enough to get good yields. I'm gonna search altavista to see if HBr is compatible with synthetic rubbers and similar materials. Peace!
I'm going to help all of you cleanse this diseased planet.
(Hive Addict)
04-18-01 21:56
No 185187
Well if you say so.
Look at it this way.
1. You will have to babysit the acid (HBr) production if you use your infamous raft method.
2. You will have to slowly bubble the HBr into the safrol/acetic
Why not just do both at the same time???
Ever hear of two birds with one stone?
Do Your Part To Win The War
(Hive Bee)
04-19-01 08:41
No 185272
just one possible problem: will your HBr generator produce just HBr or will some Br2(g) be formed as well. The Bromine might fuck up the process by making some di-bromosafrole. There is a thread about this in chemistry discourse called HBr bubbly bubbly..
Is there any way to get rid of any bromine gas that might be in the HBr?
Happy Rafting!
--Preventing odors from escaping to nearby noses is essential.....
(Hive Bee)
04-19-01 09:06
No 185278
"Is there any way to get rid of any bromine gas that might be in the HBr?"
Add a little dH2O to the NaBr before starting the H2S04 drip?
"You will have to slowly bubble the HBr into the safrol/acetic"
Hook-up an off/on valve between the HBr and flask. Or, I could just give-up on my raft idea.
I'm going to help all of you cleanse this diseased planet.
(Hive Bee)
04-19-01 09:29
No 185283
IMHO, give up on the raft. it sounds dangerous. don't put a valve in the line either, as it will pressurize your gas vessel and might cause it to rupture. just drip in the sulfuric when you want gas produced, using a sep funnel.
If pacman influenced us, we'd glide around dark rooms eating pills and listen to repetitive music.
(Hive Bee)
04-20-01 20:34
No 185613
"just drip in the sulfuric when you want gas produced, using a sep funnel."
In other words, keep it simple! Thanks and peace!
I'm going to help all of you cleanse this diseased planet.
(Hive Bee)
04-21-01 16:53
No 185772
The NaBr and H2SO4 produces nearly all Br2, relatively little HBr:
NaBr (s) + H2SO4 (l) HBr (g) + NaHSO4 (s)
2HBr (g) + H2SO4 (l) Br2 (g) + SO2 (g) + 2H2O (l)
In SWIMs experimental procedures, even producing the gas in an ice water bath or with chilled acid results in load of Br2 and very little HBr (HBr is colorless but goes cloudy white on exposure to air, white wisps in red gas signify small amt.s of HBr in with Br2)
SWIMs other experiemnt was HCl + NaBr. This resulted in an extremely small amount of redish gas (it looked yellow at low conc.), and a whole lot of gas that went cloudy white when hitting the air. Just to check that this wasn't HCl gas, it didn't react with ammonia vapor. SWIM is almost sure that this is HBr, chemistry chat rooms have agreed.
This gas was bubbled into sassy, which started out yellow and then went green progressing then into dark green. Small amounts of red oil were viewed in splashes on the upper portion of the test tube, but the majority of the sol'n was dark green, almost black. These color changes are nearly exactly what's to be expected when bromosafrole is made with KBr and DMSO. Interesting, what do you think? Also, see thread in chemistry forum "HBr bubbly bubbly"
PS, closer examination has revealed that the oil is indeed redish, but very very very dark, probably contanminated by gas generator, bubble-tube was stainless steel, but has given problems before.
blah blah blah something clever blah blah blah
(Hive Bee)
04-21-01 22:35
No 185830
"These color changes are nearly exactly what's to be expected when bromosafrole is made with KBr and DMSO. Interesting, what do you think?"
Damn! A while back, I was asking how one could make their own bromine, and the answers were more complex than just adding H2SO4 to KBr/NaBr. Are you sure about that? I've heard that the production of bromine can be avoided, and HBr produced by slowly adding the H2SO4 to a chunk of NaBr that has been moistened with a little H2O?
When H2SO4 is added to KBr and DMSO, HBr is produced. <-- Everything in that procedure is anhydrous, so why can't I get the same results by adding H2SO4 to a dry bromide?
Your HCl + bromide idea sounds good to me. Some excess HCl would probably end-up being mixed with the safrole. I wouldn't worry about that, because it's very hard to get HCl to react with safrole..The HBr would get the job done way before the HCl. What does everyone else think? Peace!
I'm going to help all of you cleanse this diseased planet.
(Hive Bee)
04-21-01 23:02
No 185836
R.e. the color changes, I was refering to the color changes decsribed when bromosassy is made via the frozen DMSO method with KBr, I was trying to show that the gassing was indeed producing the bromo safrole.
About the Br2, I tried H2SO4 and NaBr (anhydrous or nearly) once cold and once at room temp. Each time copious amounts of Br2 was produced. The mechanism for this Br2 production was found at
http://www.webelements.com/webelements/e
It states there that the "reaction conditions" oxidize the HBr to Br2, however it fails to elbarote on which conditions cause this, and it appears that chilled or not chilled had no effect.
Perhaps you are right about using moist NaBr and H2SO4, however I tried moist NaBr once and I saw the characteristic orange creep beginnig so I trashed it before it got going.
Youre indeed right about the HCl in the HBr made from NaBr and HCl. I don't think the amount of HCl is all that large. Then again it makes no difference, even if it did react, chlorosafrole would probably behave in the same manner as bromo so it's not a problem.
blah blah blah something clever blah blah blah
(Chief Bee)
04-22-01 08:57
No 185929
Both HBr and HCl will react with ammonia gas, forming ammonium chloride or ammonium bromide. If you didn't get any reaction, then your gas is not HBr or HCl, but something else.
http://rhodium.lycaeum.org
(Hive Bee)
04-22-01 09:43
No 185941
Oh, I'll generate some more and test it with the ammonia again, never really liked that test anyway.
blah blah blah something clever blah blah blah
(Hive Bee)
04-22-01 18:26
No 186037
"About the Br2, I tried H2SO4 and NaBr (anhydrous or nearly) once cold and once at room temp. Each time copious amounts of Br2 was produced."
Damn, thanks man! In my dreams, you saved me from a big-time failure. Peace!
I'm going to help all of you cleanse this diseased planet.
(Hive Addict)
04-22-01 21:22
No 186058
The NaBr and H2SO4 produces nearly all Br2, relatively little HBr:
NaBr (s) + H2SO4 (l) HBr (g) + NaHSO4 (s)
2HBr (g) + H2SO4 (l) Br2 (g) + SO2 (g) + 2H2O (l)
In SWIMs experimental procedures, even producing the gas in an ice water bath or with chilled acid results in load of Br2 and very little HBr (HBr is colorless but goes cloudy white on exposure to air, white wisps in red gas signify small amt.s of HBr in with Br2)
But you weren't using pure NaBr. You were using a mixture of NaBr and an oxidizing agent whose purpose in the mixture is to oxidize the bromide to bromine. Post 185107 (Agent_Smith: "Re: HBr bubbly bubbly", Chemistry Discourse)
(Hive Addict)
04-22-01 21:35
No 186060
"About the Br2, I tried H2SO4 and NaBr (anhydrous or nearly) once cold and once at room temp. Each time copious amounts of Br2 was produced."
Damn, thanks man! In my dreams, you saved me from a big-time failure. Peace!
Actually, Agent_Smith is throwing you a bit of a red herring by leaving out important experimental information - namely that he doesn't have pure NaBr but a mixture containing an oxidizing agent.Post 185107 (Agent_Smith: "Re: HBr bubbly bubbly", Chemistry Discourse)
Vogel prepares hydrobromic acid from from KBr and sulphuric acid. For anhydrous HBr he uses direct combination of the elements or the action of bromine on tetrahydronaphthalene.
(Hive Bee)
04-22-01 21:59
No 186065
wont the sulfuric + KBr produce anhydrous HBr if it works as said?
If pacman influenced us, we'd glide around dark rooms eating pills and listen to repetitive music.
(Hive Bee)
04-22-01 22:56
No 186075
I apologize, I forgot to mention in this post that my NaBr was mixed with a slightly smaller molar amount of dichloro-s-triazinetrione. I still maintain, however, that gaseous HBr will be difficult to produce with the H2SO4 and NaBr method. ( 2HBr (g) + H2SO4 (l) --> Br2 (g) + SO2 (g) + 2H2O (l) )
Nevertheless, I'd love to make it work as much as the next guy, so I've obtained 99% NaBr and will give the H2SO4 method a shot tommorrow, and let ya'll know how it goes.
blah blah blah something clever blah blah blah
(Stoni's sexual toy)
04-23-01 02:32
No 186108
I still doubt that adding HCl to NaBr will produce HBr. At best you will end up with a 50:50 mixture of HCl and HBr.
(Hive Bee)
04-23-01 05:33
No 186142
I posted this in the chem forum "HBr bubbly bubbly", thought it would be of interest to this thread:
"Okeeeokdeee, a small amount of NaBr (99%) was placed in a beaker, and covered with conc. H2SO4. This immediately foamed and released a creamy orange gas (sorta the color of orange sherbert). After 30 seconds the reaction began producing more orange gas, until at about t=60seconds the beaker issued a lot of bromine and apparently little HBr. Probably 'cuz things heated up.
This worked only slightly better than the previous experiment with the triaz. mixed in. Will try again with chilled reactants, although given the heat of the beaker after this trial was over, I'm not sure ice water is gonna cut it, this seems very exothermic.
Since to get good yields the HBr should be bubbled slowly, I still like the HCl method better, it *seems* less exothermic, and keeping the H2SO4 method cold for a long time is gonna be a pain. I'll try to find a reference for the HCl and NaBr reaction.
Chilled H2SO4 test to come..."
Os, why do you think 50/50?
blah blah blah something clever blah blah blah
(Hive Bee)
04-23-01 07:51
No 186170
In "Total Synthesis 2" --> 240g potassium bromide is dissolved in 400ml water. After this is chilled, 180ml H2SO4 is slowly added, keeping the temp. below 75*C to prevent the formation of bromine, and this is distilled to give 48% hydrobromic acid.
----------------------------------------
Here's my idea: Saturate the 48% HBr with sodium chloride, and slowly drip H2SO4 from a sep funnel to produce slightly damp HBr. This could be lead into a chilled flask of acetic acid until it can't hold anymore HBr. A little water won't hurt just as long as the HBr's concentrated enough to be of use in producing bromosafrole. So, what do ya think?
I'm going to help all of you cleanse this diseased planet.
(Hive Bee)
04-23-01 09:21
No 186196
Hiya,
I should have mentioned something earlier, but I just never got around to it. Please, do yourself a favor, and put your energy towards something that will work. You're banging your head against a wall with this one, since you are not going to be able to produce gaseous HBr this way, no matter what. Period. Sure, sulfuric acid and KBr will give you aqueous hydrobromic acid, but you'll never be able to produce hydrogen bromide, the gas. The little KBr/H2SO4 technique is the laboratory preparation method of choice for aqueous HBr, as outilined in Inorg. Syn. 1, 155 (1939), but there is a reason why the only preparations for anhydrous HBr involve the fusion of elemental hydrogen and bromine at elevated temperatures, or the bromination of Tetralin(R) - and the reason isn't that they had nothing better to do with their time. Its not that they're gluttons for punishment or exceptionally anal about purity, its just the only way that works. It all comes down to dissociation constants and the competing ion effect.
Let it go, for your own good...
(Hive Bee)
04-23-01 12:56
No 186263
I disagree... a reaction obviously occurs when H2SO4 and NaBr are anhydrous or nearly so. Thus, any HBr is given off as a gas.
Purity is a big problem here though, thats why HBr gas is produced in the manners you say.
blah blah blah something clever blah blah blah
(Hive Addict)
04-23-01 16:14
No 186311
can you not just brominate it to the dibromo safrole and then decompose this with heat???
Solves all the problems
Do Your Part To Win The War
(Hive Addict)
04-23-01 19:00
No 186348
Os, why do you think 50/50?
Allow me to be a bit presumptuous and answer for Osmium:
Because HBr is extremely soluble in water just like HCl. There is nothing to drive the equilibrium in one direction or another. All that you will end up with is a flask of water containing Na+, H+, Cl- and Br- ions in aqueous solution.
(Hive Bee)
04-23-01 19:15
No 186353
I remind you that everything I've discussed here is anhydrous, the water form adding HCl (aq) is negligable, once saturated with HCL OR HBr, it fumes off the rest.
blah blah blah something clever blah blah blah
(Hive Bee)
04-23-01 19:40
No 186368
Jesus Fucking Christ! What does a guy have to suck to get some fucking HBr!? Alright, lets say you made some 48% HBr that's contaminated with a little Br. Add some sulfur to this and apply heat, which will convert the Br to HBr. Add some more sulfur, so that while dripping H2SO4 if Br's created from over-heating, it'll be converted back to HBr. Just to be safe, have the HBr go through another flask containing sulfur, then lead it to the acetic acid? Would H2SO4 react with sulfur?
Or, could the impure HBr be bubbled into the acetic acid, then sulfur be added without anything fucked-up happening?
I'm going to help all of you cleanse this diseased planet.
(Hive Bee)
04-23-01 20:00
No 186378
This aint hard... all these mthods make HBr, pick you poison:
H2SO4 and NaBr: makes HBr but risk high Br2 formation, and thus dibromo. cooling reduces br2 formation
HCl and NaBr: make HBr but also HCl giving bromo and chlorosafrole mix (light on the chloro)
buy 48% HBr: bromosafole can still be made with the aqueous stuff, see http://rhodium.lycaeum.org/chemistry/hal
blah blah blah something clever blah blah blah
(Hive Addict)
04-23-01 21:53
No 186406
I remind you that everything I've discussed here is anhydrous, the water form adding HCl (aq) is negligable, once saturated with HCL OR HBr, it fumes off the rest.
Sigh, you just don't listen. Hydrochloric acid is hardly anhydrous. Reread my last post and try to pay attention to what is being said. But, if you don't want to, then I wish you much happy windmill tilting.
(Hive Bee)
04-24-01 04:57
No 186445
Terbium:
I don't want to be confrontational, however if you read Os's post, he said the GASES are 50/50, so your presumption that no HBr(g) is produced... I can't believe it.
Also, I aknowledge, quantitatively, youre correct, 33% HCl brings roughly 100ml H2O/mole HCl and produces 80.9g HBr/mole HCl upon reaction with NaBr. Since HBr is almost 200g/100ml soluble, you're correct that all the HBr could dissolve.
Qualitatively, however, experimental procedures reveal that this reaction does in fact produce gas, and lots of it. I could measure the volume of gas to show that more gas is produced that could be theoretically all HCl, however, even you must agree that that isn't the case:
Another quantitative analysis shows that HCl is 62g/100ml soluble, so 33% HCl is only 1/2 the way to saturation. As such, there would be plenty of water to dissolve all the HCl produced as well. By these numbers, there should be NO gas at all, and that is certainly not the case.
I conclude that this reaction produces:
a) lots of gas (which quantitatively, it shouldn't)
b) at least a fraction of it is HBr
That's my thinking, seems sound to me...?
blah blah blah something clever blah blah blah
(Stoni's sexual toy)
04-24-01 06:12
No 186455
As someone said before, you will end up with a solution containing Na+, H+, Cl-, and Br-.
The question now is: since this solution is above saturation, which molecule will be given off? Since HBr is less volatile than HCl, I would expect the HCl to be the mayor component of the gasses. What means mayor? How much? I don't know, that's why I said 50:50. Probably the HCl content will be even higher.
Those solubility numbers you gave up there don't mean much, they are for the pure gasses in pure water.
What we have here is a multi-component mixture, with the Na anions being non-volatile, so whatever happens, they will of course stay in solution. Which gas composition will be given off is hard to say, but it will most certainly be a mixture of both gasses, and the HCl will be the main component.
I'm not trying to discourage anybody, but if you want to try the HBr route, then steer yourself to the serious chemistry forum, and search for the procedure I posted there, which gives over 90% bromosafrole. There is a reason why this HBr shit isn't used widely on these boards.
(Stoni's sexual toy)
04-24-01 06:14
No 186457
> can you not just brominate it to the dibromo safrole and
> then decompose this with heat???
No, doesn't work. Even if that was a clean reaction this would split off HBr from the molecule, and you will end up with a double bond somewhere.
(Hive Bee)
04-24-01 07:32
No 186466
Agent_Smith,
Like I said, it won’t work. I’m trying to figure out where to begin clarifying, but I'm overwhelmed.
First off, let’s scrap this nonsense about HCl + HBr making HBr. Compare, if you will, the pKa’s of the two acids. Oh, you can’t find those numbers? Well, let your good friend Smiley_Boy help you out (the pKa for HBr can be surprisingly elusive when you’re first starting.) The pKa for HBr is around –8.6, and the pKa for HCl is near -7.4 (or so IUPAC would have us believe.) Notice something? Yes, the pKa of HBr is lower, meaning that in fact HBr is about 20 imes more acidic, and indicating that in a mixture the cation (Br-) will generally stay ionic, and that HCl will generally be in far higher concentrations than HBr. To rephrase this, you're not going to get a lot of HBr this way.
Let’s also clear up the matter with ammonia fumes. I have some doubts about the way this experiment was performed, since both HCl and HBr form salts with ammonia. The fact that you got nothing certainly doesn’t indicate that HBr was produced. Rather, the fact that you got nothing indicates the test was performed in a manner that it was not intended.
Moving on, let’s straighten this business out with Osmium, and your quotation of him. Not once in his message did he use the word 'gases', and 50/50 'at best' was what he suggested. He was being polite, but at the same time, he was trying to tell you this is a dead end. Osmium is a nice guy, but parroting him certainly isn’t exactly the stuff of science. Why 50/50? You tell me. Oh, you can’t? Well, neither can I; as far as I can tell, Osmium pulled this number out of thin air, in an effort to explain the reason why the best-possible-scenario with this procedure is still unacceptable.
Now, let’s get into the meaty part:
Another quantitative analysis shows that HCl is 62g/100ml soluble, so 33% HCl is only 1/2 the way to saturation. As such, there would be plenty of water to dissolve all the HCl produced as well. By these numbers, there should be NO gas at all, and that is certainly not the case.
Wow, this makes me nervous.
Okay, let’s go through this, step-by-step. Now what is that whole “%” all about? It’s the percentage of how much of the weight of the solution is made up by HCl. How do we calculate it? Well, let’s say that water weighs about 1 g/ml (certainly close enough for this demonstration.) That means that the solution weighs 162 grams (62 g HCl, plus 100 g H2O). Now, calculate:
(62 g HCl)/(162 g solution)*(100%) = 38.2%
Which, according to the Merck Index, is actually about as much HCl as water can hold under ambient conditions (BTW, if you haven’t picked up a copy of it, do so. It will save you a lot of grief and energy - and chemicals.) Incidentally, a saturated HBr solution is made up of 66% HBr.
I want to make sure you know I don’t mean this at all in a discouraging manner; though I think your understanding of theory could use some polishing, you’ve shown a great deal of promise in practical lab technique. The fact that you went out and actually took some carefully measured direct observations -- that's impressive. I really look forward to seeing your progression.
I hope this helps...
(Hive Bee)
04-24-01 08:45
No 186474
...Plus, I can't imagine that the bromine is going to stay away from that benzene ring for very long, in particular the 6-position.
(Hive Bee)
04-24-01 10:05
No 186488
how about these apples. bubble H2S into cold water until it is saturated. next, drip sulfuric acid onto NaBr or KBr and bubble the resultant fumes into the H2S saturated cold water. that way, any HBr produced will stay in the water, and the Bromine that passes over will react with the H2S to form HBr. should work in theory, works for HI production.
oh yeah, wear SCBA gear if you want to be able to carry on with the bromination procedure.
If pacman influenced us, we'd glide around dark rooms eating pills and listen to repetitive music.
(Hive Bee)
04-24-01 13:23
No 186518
Ok, ya got me :) Thanks to everyone for keeping the "flames low"...
To head back to reality now, does anyone have any data for ratio of Br2 to HBr production at various temperatures with the H2SO4 method?
Ok, I just thought of something, so I'll hafta diverge a little bit back to the imaginary. I see that Br2 reacts with H2O to form a mix of HBr and HBrO (and heating or exposing HBrO to sunlight gives HBr) (http://www.ucc.ie/ucc/depts/chem/dolchem
blah blah blah something clever blah blah blah
(Hive Bee)
04-25-01 07:05
No 186731
Check this out: http://l2.espacenet.com/dips/viewer?PN=G
Pat. GB551789
Process for preparing hydrobromic acid
I'm going to help all of you cleanse this diseased planet.
(Hive Bee)
04-25-01 08:23
No 186747
To head back to reality now, does anyone have any data for ratio of Br2 to HBr production at various temperatures with the H2SO4 method?
You're overlooking something here: The oxidation potential of H2SO4 (or any oxidizer) depends on the activity, which itself depends on the concentration!
If you look at a table of standard potentials you will see that Cu is not oxidised by 1M (or was it 1N??) H2SO4, still you can dissolve Cu with conc H2SO4.
So the problem will not only be temperature but (and foremost?) concentration!
(Hive Bee)
04-25-01 10:27
No 186784
Ok, say one has a pile of bromine and wants some HBr(g). I don't have a copy of Vogel around but i think i remember reading something about this. Do you just add sulfur and bromine to get HBr? You can get bromine very easily by adding oxone to NaBr solution...
what about creating a small jet of hydrogen gas via electrolysis of water and placing the capillary tube with the hydrogen flame into the flask with the bromine? Just light the hydrogen jet and then place it into the bromine. (extreme caution should be taken when working with hydrogen gas. Small scale only!) This should theoretically work right? I don't know exactly how to set something like this up though, will probably explode if it isn't set up right. Mabe you guys should check out festers method of bubbling HCl(g) into Safrole/GAA/48% HBr mix to cause dehydration of the acid. Ritter says it works, SWIM tried it once but didn't bubble enough gas and used HBr that was too weak so no reaction took place.
Don't bang your heads against the wall too much with this one bees, SWIM has had many a head banging experience with this method!
-improv
--Preventing odors from escaping to nearby noses is essential.....
(Hive Bee)
04-25-01 14:30
No 186851
what conditions are needed to combine elemental hydrogen and bromine into HBr? say, if one were to run an electrical current through a saturated solution of KBr in distilled water and pipe off the gas produced at the negative electrode, how hot would you have to get it for the two to combine, and would more than atmospheric pressure be needed?
If pacman influenced us, we'd glide around dark rooms eating pills and listen to repetitive music.
(Hive Bee)
04-25-01 14:42
No 186855
Good questions! Now we're getting somewhere. Okay, so what are we looking at as far as equilibria? Well, under aqueous conditions, with a mixture of Br2 and HBr, we have the following:
H-Br (hydrogen bromide) + H-O-H (H2O) <-> H3O+ (hydronium anion) + Br- (bromide cation)
Br-Br (elemental bromine) + H-O-H (H2O) <-> H-Br (hydrogen bromide) + HOBr (hypobromic acid)
and, we have the following reaction:
2 HOBr + (UV light) -> 2 HBr + O2
Now, when you add bromine to water, you get an equilibrium, where Bromine dissociates and reacts with one equivalent of water, forming one equivalent of hydrobromic acid, and one equivalent of hypobromic acid. After awhile, the HBr and HOBr react with each other, and the product is H2O and Br2. This goes on and on, back and forth, countless times in the solution, and its a relatively stable pattern.
Now if you shine some strong UV light source on the solution (like sunlight), something else happens. The light causes an irreversible reaction to happen,so that O2 gas and HBr evolve. Since the solubility of O2 in solution is only about 9 mg/L, it bubbles off quite quickly. However, like it was said before, a saturated HBr solution is 66% HBr, meaning you'd have to produce a hell of a lot of HBr before the solution wouldn't hold any more, and then you'd still have to separate HBr from the Br2 fumes. Also, you'd need a lot of light, or a lot of time, or both. In theory at least, it should work, but it sure sounds messy.
Hey, here's an idea:
NaBH4 + 4Br2 + 3H2O -> 7HBr + NaBr + B(OH)3
Now, to keep it relatively anhydrous (not completely anhydrous per se, since 3 equilvalents of water are used), we need a relatively innert solvent that will dissolve the starting materials well, but not the final products (well, at least not dissolve the HBr well, anyway.) Glyme or diglyme or even THF sound like fine candidates. If everything is kept relatively cold, perhaps by chilling the NaBH4/glyme solution using ice and rock salt, then one could add elemental bromine with a pressure-equalized addition funnel. Perhaps by adding the bromine and water in series, the borohydride wouldn't have to compete for solvation against boric acid. Hmmm...
Step 1:
NaBH4 + 4Br2 -> 4HBr + NaBr + BBr3
Step 2:
BBr3 + 3H2O -> 3HBr + B(OH)3
It looks like this might work, but I have a funny feeling I'm overlooking something somewhere. To the other killer bees: does this look reasonable? Am I somehow forgetting some crucial side-reaction? I mean, this isn't all that great of an alternative, but would this work?
To Agent_Smith: I just wanted to appologise again too, in case I sounded rude in my last response. I have to admit, sometimes I forget my manners. I'm sure you know that we're all on the same side of this terrible war. I took the time to give a thoughtful answer, which I genuinely hope you enjoy and find useful. I'd hate for that effort to go unappreciated, simply because of some of my bad choices in phrasology.
(Hive Bee)
04-25-01 20:15
No 186906
Fear not smiley_boy, I appreciate all your help, and I'm not fragile enough to be tweaked by tone.
I'll finally concede that the gaseous HBr bubbly method isn't hot shit, so my research into using aqueous HBr has borne this fruit:
Safrole (5.3 g.) added dropwise at 0C to 21 g. 70% HBr, the mixt. left 14hrs. at 0C, poured on ice, extd. with Et20,and the ext. distd. in vacuo yielded 97% 3,4-CH202C6H3CH2CHBrMe (I), n D-24 1.5634.
Chemical Abstracts 1961, column 14350, paragraph e (S.Biniecki &E.Krajewski) - Safrole + 70% HBr at 0C for 12hours produced 97% yield of bromosafrole.
Journal of Chromatographic Science, Vol. 29, april 1991, page 169: Bromination Reactions. Samples of sassafras oil or alkenes (5.0 g of safrole, isosafrole, eugenol, isoeugenol, etc.) in 48% HBr (25 mL) were stirred at room tempature for 7 days. The reactions were then quenched with the addition of crushed ice (25 mL) and extracted with ether (2 x 50 mL). The ether extracts were evaporated to dryness under reduced pressure and the resultant product oils analyzed directly.
FROM "The Journal of Chromatograpghy science, Vol 29, 1991, page 267-271:Bromination with 48% HBr (aqueuos). Stirred for 7 days @ room tempature. Quanities- 5 grams safrole, 25 mL 48% HBr. Quenched with 25 mL crushed ice and extracted with ether.
Wow, 97% yield without that DMSO crap. Interesting.
Also, when making aqueous HBr, the H2SO4 and NaBr will work fine, right?
blah blah blah something clever blah blah blah
(Hive Addict)
04-25-01 23:39
No 186975
Also, when making aqueous HBr, the H2SO4 and NaBr will work fine, right?
According to Vogel, you want to keep the temperature below 75°C.
(Stoni's sexual toy)
04-26-01 01:01
No 186992
> Step 1:
> NaBH4 + 4Br2 -> 4HBr + NaBr + BBr3
All that HBr formed in that first step will lower pH dramatically, which means the bulk of the NaBH4 will be lost to hydrolysis.
I don't think it will work.
(Hive Bee)
04-26-01 05:03
No 187041
Ok, keep it below 75C.
How much water to use? should I calculate an amount that will relate to a final 66% HBr sol'n (which I believe is the max). Or should I dilute the stuff even more than that and then distill?
blah blah blah something clever blah blah blah
(Hive Bee)
04-26-01 07:24
No 187063
Os,
Thanks for your input. Actually, I thought about the hydrolysis problem, which was why I suggested diving the reaction up into two steps - the first being the reduction of Br2 with NaBH4 under anhydrous conditions, followed by quenching with H2. If the conditions are kept anhydrous during the addition of Br2 to NaBH4, then hydrolysis isn't possible. In other words, Br2 is added to an anhydrous solution of NaBH4 in some inert solvent; perhaps the reaction could even be done hetergeneously to minimize the amount of solvent needed. After all of the Br2 has been allowed to react with NaBH4 (indicated by the absence of Br2's characteristic color), the solution is then hydrolyzed by careful addition of water. So, step 1 is the treatment of one equivalent of NaBH4 with 4 equivalents of Br2, yielding 1 equivalent of NaBr, 1 equivalent of BBr3, and 4 equivalents of HBr. Step 2 is the hydrolysis of BBr3 with 3 equivalents of water or alcohol, yielding the final 3 equivalents of HBr. What do you think?
(Hive Bee)
04-26-01 07:44
No 187067
Huh?! I don't get it; in some posts, you sound like you're a early-yet-promising beginner, but in posts like this, you sound like a flaskjockey who's been doing this for awhile - what's the dealio? Is there more than one person posting on this account?
The safrole and 70% HBr looks interesting, except that 70% HBr isn't the easiest or cheapest thing to come by. ACtually, I think that article has been discussed at length here on the Hive in the past.
I don't think I've seen that J.Chrom.Sci. article before. It looks nice; the reaction time is a little long, but reasonable. 47% HBr is something obtainable (readly obtainable from KBr and H2SO4, which can be followed up by distillation to get a reagent of very high purity.) I'm kinda wondering about this, since safrole and aqueous HBr solution isn't going to mix well.
(Hive Bee)
04-26-01 07:57
No 187069
This reduction of bromine with elemental sulfur certainly sounds clever! I'm guessing that the stoichiometry would go something like this:
S + 3H2O + 2Br2 -> 4HBr + H2SO3
or,
S + 4H2O + 3Br2 -> 6HBr + H2SO4
It sounds a little smelly and dangerous, since undoubtedly a little H2S will also be generated due to incomplete oxidation. Maybe if the sulfur is added to an excess of Br2? Hmmm...
(Hive Bee)
04-26-01 08:50
No 187081
In Total Synthesis 2(page 255-256), Strike shows an HBr synth she found in Vogel's "Practical Organic Chemistry":
"48% HBr: Method 3 (from bromine and sulphur)
A 1-litre three-necked flask is charged with 27g of flowers of sulphur and 550ml of H2O. The flask is equipped with a dropping funnel(with tip below the surface of the water), a water sealed mechanical stirrer and an Allihn reflux condenser; Ground glass joints are preferable, but used rubber stoppers are generally satisfactory. The flask is immersed in a bath of water at 60*C, the mixture stirred vigorously and, when the temp. inside the flask is about 50*C, 400g(125.5ml) bromine are introduced from the dropping funnel during about 20 minutes. The temp. of the reaction mixture rises rapidly as the reaction proceeds; the flask is cooled momentarily in a bath of cold water if the condensed bromine vapour is near the top of the condensor. When all the bromine has been added, the mixture is heated on a boiling water bath for 15 min.. The reaction product is cooled, and filtered from residual sulphur and other solid matter through a sintered glass funnel. The filtrate is distilled and the constant b.p. hydrobromic acid collected at 125-126*C/760mm. The yield is 805g.
Note: The reaction between bromine and sulphur in the presence of water may b represented by the equation:
3Br2 + S + H2O = 6HBr + H2SO4
It is rather slow at moderate temps. and the hydrobromic acid formed in the initial stages of the reaction inhibits it's further progress. Bt carrying out the reaction at 50-70*C or above in the presence of a large excess of water, the inhibition observed at lower temps. does not occur."
----------------------------------------
To me, the above synth seems pretty fucking useless for making a concentration above 48%, so right now I'm thinking that bubbling anhydrous HCl through 48% HBr/safrole is the best way to go(at least 2nd in line to the DMSO method) Is any other solvent that can be used in place of that smelly-ass DMSO?
Getting back to my earlier idea: H2SO4 + 48% HBr that is saturated with NaCl creates bromine and HBr - If this gas could be passed over a dry material that binds bromine, but not HBr, then I'd be all set.
By the way, if [b]dibromo
I'm going to help all of you cleanse this diseased planet.
(Hive Bee)
04-26-01 21:07
No 187186
No no, only one person posting, and I am a beginner. I have a good amount of chemistry education under my belt though, but I never really liked it. So, for exmaple, when I got flamed for missing the importance of the dissociation constants of HCl vs HBr, I'm fully capable of making those calculations and understanding them, I just fail to make the intial connections 'cuz I never took much time to understand the "why this is important", but rather just focused on "how do I get an A?"
I was wondering about the sassy and HBr(aq) phases myself. I read somewhere that when the reaction is complete, the solution becomes one-phased and turns red...?
One thing I would like to lnow is how does the rate of this reaction proceed? Logic to me dictates that it proceeds quickly at first then slows as time progresses (since rate is based on concentration of reactants). So if it takes 7 days to completely brominate safrole with 48% HBr, at 3.5 days, the yield is >50% ? Or is the progression linear?
blah blah blah something clever blah blah blah
(Hive Bee)
04-27-01 14:31
No 187386
If you own Uncle Fester's "Secrets of Methamphetamine Manufacture", then check out pages 166 & 167. Dry HBr is produced by dripping 48% HBr onto phosphorus pentoxide..I'm not sure if that's good news, because I can't find a source for this. The best I could find was phosphorus oxychloride, and I doubt this would be of any use?
I'm going to help all of you cleanse this diseased planet.
(Chief Bee)
04-27-01 15:07
No 187399
48% HBr on POCl3 would result in the water in the acid reacting with the POCl3 like this: POCl3 + 3 H2O => H3PO4 + 3 HCl
With P2O5, the water would react like this: P2O5 + 6 H2O => 2 H3PO4
http://rhodium.lycaeum.org
(Hive Bee)
04-27-01 16:06
No 187419
Okeedokee, in classic Agent_Smith fashion, I'm gonna charge ahead with a reaction without accounting for all the parameters.
Heres what my dream will be:
103g 99% NaBr will be dissolved in 169ml of dH2O. Then, about 103g of my "concentrated H2SO4" will be added.
This will make 81g or so of HBr in 169ml of H2O is around a 48% sol'n. There will also be 120g or so of NaHSO4 in sol'n, but I'm not gonna distill, I'm just gonna ignore that.
So then my ~48% HBr will be put in a champagne bottle, and 30g of safrole will be added. This will be sealed and placed on the swirler for 7 days.
Good idea, eh? If all goes well, the mix should turn red and homogenize, as is reported by other similar reactions.
blah blah blah something clever blah blah blah
(Hive Bee)
04-27-01 17:52
No 187440
Ok, dropped in the H2SO4 to the chilled (~5 degrees C) NaBr sol'n. It heated itself up and was placed in the freezer to cool it down. Gas emitted was minimal.
When removed from freezer, it was a nice clear sol'n, and ~30g sassy was added.
Interestingly, during the sassy addition, a bunch of white precip was noticed about the bottom of the bottle... A lot! A small amount of the acid was placed in a beaker, and swirled around, and wherever the acid evap.ed, a crystaline something was left behind... hmmm, NaHSO4 perhaps? That's probably whats in the bottom of the bottle as well. No matter, it's still in there when the bottle was sealed, don't forsee any probs.
So now the bottle will be swirled for 7 days or so... so far so good, only that white precip. seems to be non-bueno.
UPDATE: The bottle showed no reaction when left sit for a few hours. After it was placed on the swirler, the oil layer appeared to turn red (dark bottle makes it hard to tell, but the oil changed to a dark color) in about 10 minutes. Also, the HBr seems to have turned cloudy, but this may be suspended oil. The crystaline suspected-NaHSO4 remained in a solid chunk at the bottom of the bottle, and is unaffected by siwrling. How does this sound?
blah blah blah something clever blah blah blah
(Hive Bee)
04-28-01 01:57
No 187554
nice waste of sassafras oil there. sulfuric acid bonds to 2 molecules, forming Na2SO4. that probably means you added too much sulfuric acid. sassafras oil decomposes upon exposure to sulfuric acid, which accounts for the dark red you noticed. next time distill it.
If pacman influenced us, we'd glide around dark rooms eating pills and listen to repetitive music.
(Hive Bee)
04-28-01 08:52
No 187607
Damn. But please help me learn here:
sulfuric acid bonds to 2 molecules, forming Na2SO4
I expected it to form a salt, however I didn't think it would be a problem. Althought I predicted NaHSO4, why do you say Na2SO4? Not much gas at all was given off in this reaction, and since I used about a mole of everything, there certainly wasn't any gas in an amount similar to the amount of H that'd be released when Na2SO4 was formed.
that probably means you added too much sulfuric acid
I calc'd a slight excess of NaBr, if anything, I thought I added too little H2SO4.
sassafras oil decomposes upon exposure to sulfuric acid, which accounts for the dark red you noticed
I believe sassafras decomposes on exposure to any strong acid, doesn't it? I noticed the same dark red color when I bubbled the HBr/HCl mix into it in a previous experiment
If it means anything, the sassy is slowly being digested into the HBr layer, and the HBr layer is turning darker, even after all the oil is left to settle. That seems like things are progressing correctly...?
blah blah blah something clever blah blah blah
(Hive Bee)
04-28-01 10:03
No 187620
there will be no hydrogen evolution during this reaction. it goes as such:
heat
2NaBr + H2SO4 ---------> 2HBr + Na2SO4
water
if you calculated a slight excess of NaBr, but used a 1:1 molar ratio to base your calculations on, then there was too much sulfuric. sulfuric acid forms a diatomic(?) salt with bases, meaning that each molecule of sulfuric bonds to 2 molecules of the base.
as far as sassafras decomposing on exposure to all strong acids, the only two I suspect a problem with would be sulfuric and maybe concentrated hydriodic.
If pacman influenced us, we'd glide around dark rooms eating pills and listen to repetitive music.
(Hive Bee)
04-28-01 11:11
No 187635
Well youre very right joe, by your equation. I'm confused though about which equation is right... I got mine, with the 1:1 ratio from webelements: Post 186007 (Rhodium: "Re: HBr bubbly bubbly", Chemistry Discourse) and Rhodium shared:
"I don't think that the oil turning red is a sign of bromosafrole being formed (pure distilled bromosafrole is colorless), but rather a sign of safrole decomposition products being formed because acid is piped into it (HBr is known to break the methylenedioxy ring, and even if this reaction does not occur to a great extent if the reaction mixture is kept cool, the phenolic/quinone products formed from such a decomposition should be highly colored, so just a small amount of it will be visible in the solution). "
So which is the correct equation? If joe is right, goddamn did I add to much sulfuric!!!
(by the way, I dunno what the hells going on with the experiment now. The oil looks almost foamy, with an off-white appearance rather than the solid red it had before. It still appears to be digested into sol'n very slowly. If I did in fact use to much sulfuric, then the foamy oil is most likey decomposed safrole... shit)
blah blah blah something clever blah blah blah
(Hive Addict)
04-28-01 13:42
No 187661
So which one is correct?? I'm beginning to think I'm missing something simple, someone just tell me which equation is right?
Either or both are correct.
Didn't you claim to understand pKa? Given the molar amounts of H2SO4 and KBr added to the aqueous solution and the pKas of H2SO4 and KBr you should be able to calculate the relative concentrations of each ionic species in the solution - H2SO4, HSO4-, SO42-, HBr and Br-.
(Hive Addict)
04-28-01 14:03
No 187671
terbium
HBr is a strong acid and will completely disassociate in aqueous solution.
goiter
I doubt that the reaction goes all the way to the disodium salt
Agent Smith
Trisodium Phosphate (Na3PO4)+3H2SO4--->phosphoric acid and NaHSO4
Phosphoric acid + NaBr ---> NaH2PO4 (s) + HBr (g)
Simple/easy way to get HBr gas without Br2
Sould be a one pot shot, I doubt the salts will interfere much with the reaction.
This topic has gone on too long without good results.
If you must you can distill the acid at ~158C or lower temp with a """vacuum aspirator"""!!!
This topic is closed
Do Your Part To Win The War
(Hive Bee)
04-28-01 15:12
No 187680
Yes terbium, I understand pKa when applied to relative acid strengths, i.e. the relative amount of H+ in solution, however I don't fully understand how to apply it outside of a "which acid is stronger" situation. Given my understanding or lack there of, how do I calc. how much H2SO4 to use since one equation is a 1:1 reactant ratio, whereas the other is 2:1
Foxy2, the reaction doesn't proceed all the way to the sodium salt? Thus the thus the NaHSO4 equation is correct? What conditions would cause it to go to the disodium salt?
(your one pot shot to H3PO4 would be great if I had trisodium phosphate)
blah blah blah something clever blah blah blah
(Hive Addict)
04-28-01 16:54
No 187703
trisodium phosphate is easily avaiable at almost any paint/hardware store ect. Look for something that says "TSP". It is a common cleaner. Discontinued in laundry detergent ect but still available for specialty cleaning ie washing walls to paint ect. It is around!!!
I said it probably does not go to the disodium salt because HBr is a stronger acid than HNaSO4. Which means only one Hydrogen is able to be utilized in produceing HBr.
Do Your Part To Win The War
(Hive Bee)
04-28-01 17:23
No 187712
I've done a lot of checking around in chem chatrooms and the like, and this is quite puzzling.
People tell me that this reaction can't be assumed to go to completion. Due to psychological roadblocks and what not, I can't bring myself to understand how to calculate the correct amount of H2SO4 since there are multiple mechanisms that this reaction could follow, with different ratios. I'll assume I need to measure pH over time and stop adding acid when i reach ideal pH. So whats the ideal pH of 48% HBr sol'n?
AHA!!! By looking at other experimental procedures involving the production of HBr, like Drone's synth of Alkyl Halides ( http://rhodium.lycaeum.org/chemistry/dro
blah blah blah something clever blah blah blah
(Hive Addict)
04-28-01 19:14
No 187742
Shit
TSP is EASY to get!!!!!!!!!!!
Why use the fucked method that you are trying when it is so easy to get around it?????
I can't belive you are wasting so much effort thinking about this?
http://fry1.foxinternet.net/tips.htm
http://www.samallen.com/wwwboard/message
http://www.almanac.com/home/washthatsurf
http://www.shelfspace.com/~c-r-ffl/archi
Get out of the house and look around for TSP!
Do Your Part To Win The War
(Hive Bee)
04-28-01 19:37
No 187746
Rhodium,
Hey, that reminds me of another, sure-fire way of making gaseous HBr:
POBr3 + 3H2O -> H3PO4 + 3HBr
I'll be the first to admit that POBr3 is not cheap, nor is common. But it does look like a decent lab-prep for gaseous HBr. For the sake of thoroughness, I thought I'd add that in.
You certainly can't disagree that this method would work, though its practicality "in the field" may be limited to those priveledged enough to have accounts with Sigma, et al.
(Hive Bee)
04-28-01 19:41
No 187747
Thanks for taking the time to type that in. Yes Bwiti, that definately does appear to produce 48% HBr, and yes you're absolutely right that it won't be useful for making gaseous HBr.
Now about this business with HCl and H2SO4/NaBr, NaCl, etc. etc. etc. To tell you the truth, I can't see any of this working, though I'm trying really hard to stay open-minded. Do you have any solid reasons to justify a belief that any of those would work?
(Hive Bee)
04-28-01 20:02
No 187752
foxy2,
I disagree; this discussion should definately be continued. Yes my friend, I think we need a bit of a refresher course in pKa's. I did a quick ref search, and these are the numbers I got:
pKa HBr = -8.6
pKa H2SO4 = -1.9
pKa H3PO4 = 2.18
From source to source, you'll find variances in the numbers, but the order will remain the same, phosphoric acid is far weaker than sulfuric acid, and sulfuric acid is weaker than hydrobromic acid. If you add TSP to sulfuric acid, sulfuric acid will most certainly liberate phosphoric acid. Let's look at the balanced reaction, shall we?
2Na3PO4 + 3H2SO4 -> 2H3PO4 + 3Na2SO4
Now, what you're proposing is this:
3NaBr + H3PO4 -> 3HBr + Na3PO4
Well, that's just not going to happen. That NaBr will sink to the bottom and sit there until doomsday. Phosphoric acid is just not going to liberate it, period. Feel free to prove me wrong; I'd really like to be.
trisodium phosphate is easily avaiable at almost any paint/hardware store ect.
Actually, TSP has been banned from a large number of river watersheds around the world, especially in North America.
Do you think that such a simple solution, if it were to exist, would have evaded the all-mighty Hive?(tm) Oh, the sheer hubris of you, my lad! I chuckle heartily at the very thought. BTW, what acid are you distilling at 158 C? We're talking about producing gaseous HBr, which has a boiling point of -66.8 C -- that's the goal here.
So at this point, we still have no procedure set out that we can point at and say: this is what everybody should use if gaseous HBr is what they want to make (though I think my suggestion using Br2 and NaBH4 comes pretty close.) Our goal isn't met, but I think if nothing else, this has been an educational dialogue.
(Hive Addict)
04-28-01 20:44
No 187759
Hey Smilely Dipshit
Learn some boiling points!!! they will help you in clandestine chemistry much more than fucking pKa's.
Phosphoric acid distills at 158C smarty ooops smilely.
TSP has been banned from laundry detergent and the like but it is still available as a specialty cleaner because it works so well.
See this link. It is banned from household cleaners like laundry detergent and dishwasher soap but NOT for specialty applications. http://members.aol.com/StatutesP5/35.Cp.
Just start calling all the hardware stores in town, someone should have it. If you are in a banned area call some in the next state. I have seen it.
Do Your Part To Win The War
(Hive Addict)
04-28-01 20:59
No 187764
Hey Fuck Stick
"Now, what you're proposing is this:
3NaBr H3PO4 -> 3HBr Na3PO4
Well, that's just not going to happen. That NaBr will sink to the bottom and sit there until doomsday. Phosphoric acid is just not going to liberate it, period. Feel free to prove me wrong; I'd really like to be."
You ARE WRONG!!!!!!!!!!!
Stop trying to talk like a pro with your pKa shit.
I guess this chemistry prof has it all wrong in his tutorial he has online!!!!!!!
If you took the time to read this thread then you would have more of a clue than you do!!!
Time to take the free lesson at this link.
IT PROVES YOU WRONG http://www.rscc.cc.tn.us/faculty/ward/11
Oh yea and one more thing fuck stick, H2SO4 is stronger than HBr
Do Your Part To Win The War
(Hive Bee)
04-28-01 22:24
No 187786
I forgot all about the pKa of NaHSO4 being weaker than that of HBr. thanks for reminding me.
as far as TSP goes, the brand name for as far as I can tell does not contain any actual TSP in north america. maybe somewhere else they still sell it, but here they've determined it's pretty effective at killing fish and preventing them from reproducing. I'd like to find some to take along with my dynamite to fish with at the next greenpeace rally.
If pacman influenced us, we'd glide around dark rooms eating pills and listen to repetitive music.
(Hive Bee)
04-29-01 00:59
No 187790
Wow, calm down bees.
foxy2, I liked the TSP idea very much, however I went out today and couldn't find it! I found one product called "TSP-Aid" but on the back it said in bold "contains no TSP" I'll look some more, I'm sure it's around.
Smiley_boy: the Hcl + NaBr stuff was crap, that was my idea, there are no refs to support it. The H2SO4 + NaBr reaction is everywhere however, I've posted 4 or 5 references in this thread. My problem is that I've seen the reaction proceed two different ways, and the balanced equations use 2 different ratios of reactant:
2NaBr + H2SO4 -> 2HBr + Na2SO4
or
NaBr + H2SO4 -> HBr + NaHSO4
I gather that bother reactions are correct, however, I don't know which one works in which case, probably both. As such, since I used a 1:1 ratio of H2SO4 and NaBr, I don't know if I've used too much H2SO4 or not.
The excess H2SO4 is a problem because I'm dreaming right now, and I don't know if the excess H2SO4 in the HBr sol'n will destroy my sassy. I know I should have distilled, but I no longer have any sort of controlled heat source so it's extrememly tedious to do.
So now I have an HBr sol'n (that should be 48% or so if the reaction followed the NaBr + H2SO4 -> HBr + NaHSO4 mechanism), with sassy on top. According to that J. Chromatography article I posted earlier, this should form bromosafrole if stirred at room temp for 7 days.
Is there excess H2SO4 in my sol'n? Will it's presence destroy all my sassy, or does it act slow enough that I'll be ok? My oil is now dark, although it foams very smooth when agitated like the foam on a nice glass of Guiness. What do you think of this?
blah blah blah something clever blah blah blah
(Hive Addict)
04-29-01 01:08
No 187792
as far as TSP goes, the brand name for as far as I can tell does not contain any actual TSP in north america
Yes, for a long time I could no longer find real TriSodium Phosphate in hardware stores. There was a cleaner labeled TSP but it did not contain trisodium phosphate. Recently though I have been able to find real trisodium phosphate in hardware stores in Southern California.
It doesn't really, directly, kill fish or keep them from reproducing. The problem with phosphates is simply that they are fertilizers, essential for plant growth. Quantities of phosphates finding their way into bodies of water promote algal blooms. The algal blooms can then kill fish by consuming the available oxygen in the water.
(Hive Bee)
04-29-01 06:52
No 187868
Wow, somebody's entirely too upset!
If your arguements are that strong, I'd imagine you wouldn't need to resort to name-calling. Somehow the words 'fuck stick' just never struck me as something that I'd think would be a constructive contribution to a scientific discussion, but hey, I guess I don't know everything...
Learn some boiling points!!! they will help you in clandestine chemistry much more than fucking pKa's.
I'd have to disagree; pKa's and boiling points are both crucial in organic chemistry, depending on what a person is trying to accomplish. I really don't know what else to say to that.
Now that we have that troubled matter behind us, let's move on.
First, TSP and its availability. TSP has been banned not only from laundry detergents, but from a great deal of other places, too. As a matter of fact, a few months ago, when I needed to do some heavy-duty cleaning, I called the local hardware stores and found that they no longer carried it; in fact, it had been banned from hardware stores in my entire watershed, which occupies a fairly large chunk of the continent. I just thought you'd like to know.
As far as the tutorial online goes, this certainly is news to me. If this really works as it says, I'd like to thank you for pointing it out to me. This really is remarkable; I've looked through more secondary and tertiary literature sources for preparations of HBr gas than I care to mention, but never was this outlined. We still don't have anything resembling a set procedure, but its nice to think that this might work.
Now finally, I'd like to talk to you about your last misunderstanding.
[quote]Oh yea and one more thing fuck stick, H2SO4 is stronger than HBr[quote]
I stand by my original statement. Somehow, I remain unconvinced, despite your clever use of the term 'fuck stick'. Please, look at the pKa numbers given above, and explain to me how sulfuric acid is stronger than hydrobromic acid. I thought it was pretty straight-forward, but perhaps not.
(Hive Addict)
04-29-01 14:25
No 187934
Well i was having a bad day and ******* (i won't say it) pisses me off. Your pKa values have absolutely NO impact on this discussion. pKa vales apply to dilute aqueaous solutions which we are NOT talking about. A different measure of acid strength is necessary. One that defines the strength based on the force of attraction for a counter ion, not pKa. Read this short description of what I mean. pKa measures an acids dissociation in water, that is not necessarily the same as its strength of attraction of a counter ion. Time to sign up for a few more classes, actually it sounds like those classes hurt you more than they helped.
Here is an online discussion that illustrates my point, I didn't do a good job of making my case earlier however I knew I was right.
Question: What is the strongest acid?
How do you distinguish between two acids that are both 100% dissociated?
jim day
Answer:
Interesting question there...the strongest acids are sometimes
referred to as "superacids." These have an extremely large
proton-donating ability. Usually an acid is considered to
be a superacid if it has a proton-donating ability greater
than / equal to that of 1nhydrous (100%) sulfuric acid.
Apparently the strongest acid is hydrogen flouride (HF).
Upon reading, it seems that it is actually tough to distinguish
between the superacids on the basis of their pH alone. All strong
acids are fully ionized in dilute solution, and therefore they
all appear to have the same strength, equal to that of the
hydronium ion (h3O+), which is the most highly acidic species
that can exist in water. So all of these have the same pH on a
per-proton basis.
So, to rank superacids, chemists measure how strongly they tend to
react with a given base, B;
HA + B --> BH+ + A
This way, even superacids can be ranked relative to one another
in terms of their "strength." HF is the strongest in the table I
am looking at, followed by HSO3F, H2S2O7, HSO3CF3, HSO3Cl,
and H2SO4 (sulfuric acid).
All my data is from the McGraw-Hill Encyclopedia of Sci/Tech. -topper
Question: You say that Hydrofluoric acid (HF) is the strongest acid. However, from
what I understand its not even a super acid meaning it doesn't ionize 100%.
When I looked up the Ka value for it it was said to be 3.53X10^-4
(according to the CRC hand book of chemistry and physics) giving it a pH
of 1.73 and a %ionization of 1.8%. How can this be the strongest acid?
Different scales of acidity can give different rankings. It's all a matter
of what is being measured. It is true that HF does not fully dissociate in
water unless you add a base to it. (Incidentally, a "superacid" can be
defined in several ways; I have never before heard 100% dissociation as one
of them. The two definitions I have heard are 1. more acidic than
anhydrous AlCl3, and 2. more acidic than concentrated H2SO4.) Anhydrous HF,
however, is considered one of the most acidic substances known. This means
that it readily protonates other reference bases, even though it does not
extensively dissociate in water.
Why is this? I don't know. I imagine that it might have something to do
with hydration preferentially stabilizing HF over H+ + F-. Indirect
measurements indicate that HF is much better hydrated than any of the other
hydrogen halides. This fact alone will make it less ionized in aqueous
solution. The fact that anhydrous HF exists as hydrogen-bonded polymers
probably also has something to do with it.
Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois
========================================
Dear Ivan,
Upon rereading that answer I wrote long long ago,
I see that I made at least one error. I said that
"all strong acids are fully ionized in dilute solution."
This is much too strong a statement. There is in reality
a continuum of behaviors as one goes from weak acids
to strong acids. And many strong acids, HF being
one of them, are not 100% dissociated in aqueous solution
(although one tends to treat them that way as a first
approximation).
As I tried to explain in the message you referred to,
it is my understanding (although I could be mistaken) that
one cannot correlate the reactivity of a strong acid
with its Ka value. Weak acids can indeed be so
correlated, but not strong ones. This is, as I mentioned,
due to the fact that no acid in aqueous solution can have
a greater Arrhenius acidity than H3O+. Therefore,
one ranks the strength of strong acids according
not to the Arrhenius definition (tendency to
dissociate in aqueous solution) but according to the
Bronsted-Lowry definition (tendency to transfer a proton
to a given base in an acid-base reaction).
A superacid is not one which is 100% dissociated
but one which has a tendency to undergo BL acid-base
reactions more readily than anhydrous sulfuric acid
(this is, I believe, the IUPAC definition, but again
I could be mistaken).
I hope this helps. I suggest you consult the same primary
reference I consulted, i.e., the McGraw-Hill Encyclopedia
of Science and Technology.
Best regards,
prof. topper
dept of chemistry
the cooper union
new york, ny
Links
http://newton.dep.anl.gov/askasci/chem99
http://newton.dep.anl.gov/askasci/chem99
Fuckstick (take it as a term of endearment)
Now lets see a responce with something to back up what you have to say instead of pKa this and pKa that.
Do Your Part To Win The War
(Hive Bee)
04-29-01 15:42
No 187952
what, are you going to make flourosafrole now? do you think your glass will handle that one? maybe instead of bullshitting about who knows what and which method of ranking you should use for acid strength, why not just post the rankings of sulfuric and HBr in the presence of a base, which was the original delimna anyway? then you could decide once and for all who was correct. this pissing contest you have going on is making a nasty mess of a thread that used to be very interesting.
If pacman influenced us, we'd glide around dark rooms eating pills and listen to repetitive music.
(Hive Addict)
04-29-01 16:11
No 187958
Yea Fluorosaf now wouldn't that bee fun, and good for the teeth and bones too!!!!
I thought it was obvious that H2SO4 has a stronger affinity otherwise you would not get HBr/Br2 when you combine H2SO4 and NaBr. Hey goiter, sorry about the ranting and raveing, but there are a few good lessons in between it all (as long as you don't read any of smellys posts). This post was actually knd of dry at the start tho, it was try after try of a method that fails. Try it this way try it that way, while i admire the experimental attempts, sometimes you need to take the blinders off and look for a new way.
Hope i didn't hurt any feelings
hehehehe
Do Your Part To Win The War
(Hive Bee)
04-29-01 18:52
No 187986
Thanks to foxy and smiley_boy for that exchange, it was informative to me at least. What of this puppy I've got brewing here then? It's sassy sitting in a sol'n of HBr and an unknown amount of unreacted H2SO4, along with some SO4 salt (me thinks the salt is inconsequential). How much will that unknown concentration of H2SO4 fuck things up?
My reasoning is that it shouldn't matter, and that decomposition from the H2SO4 isn't that big of a deal. Many bromosafrole texts report yields above 95%, even though the HBr used (applied in many different forms) is known to break down the safrole in a similar fashion as H2SO4.
R.e. the futility of this method: I don't think it should be dismissed because it hasn't worked on the first few tries. Many references support whats trying to be done, its not like were pulling this out of our asses. There are methods even more cryptic than this one (pseudonitrosite?) that don't get the flame fest.
R.e. H3PO4, I've heard of this reaction many time, and tried it with NaI, however it's not as cut and dried as you think. It often requires heating to begin, and most of the time, I can't make it go at all. I'm not the only one: Post 10334 (Biscuit2: "Re: Halosaf via DMSO not working, NMR data to proove", Methods Discourse) Regardless, I shall deal with this later, what of the reaction I have in progress?
Also, if someone has time, check this out and tell me wtf he is talking about: Post 9583 (Chopper_: "Re: Halosaf via DMSO not working, NMR data to proove", Methods Discourse), Post 9993 (Chopper_: "Re: Halosaf via DMSO not working, NMR data to proove", Methods Discourse)
blah blah blah something clever blah blah blah
(Hive Bee)
04-30-01 08:26
No 188114
'Fuck stick' as a term of endearment? Must be some sort of regional colloquialism. It takes all kinds to make a world, I guess.
I'm glad to see we're all focused again on chemistry. If this HBr/HI gas generation works as well as you claim it to, I really think you have something here. I see that you brought it up once before, but I'm surprised there hasn't been more interest, especially when it comes to HI. I'm also surprised that this method isn't mentioned more often in the literature. This is really something exceptional. Well done; I really appreciate this.
Still, I have to disagree to your treatment of pKa's and their importance. The definition of 'pKa' is the negative natural logarithm of the ionic dissociation constant for a compound, and is not limited necessarily to dilute aqueous solutions; that's why whenever a pKa value is given in the literature, it usually comes with a few caveats (pKa measured at so-and-so degrees Celcius, in solvent X, in molar amounts of Y, etc.) You're absolutely right that there are many different ways of defining acids and bases, and different properties can be used to rank their strength.
Admittedly, the pKa's I used described their respective acid's activity in 1 M aqueous solutions at 25 C. And I stand steadfastly by my original statement -- under those conditions, HBr is hands-down more acidic than H2SO4. That's the quality by which I'm measuring relative acidity, its a perfectly reasonable and valid one, and by that standard, there is no other possible conclusion other than HBr is stronger than H2SO4. Period. If you truly believe that H2SO4 is stronger than HBr, I'm sure you'll be able to find hard numbers to back that statement up, and explain under which conditions this would be applicable.
I'm really not sure what you were trying to say with that quotation regarding superacids. What was that exactly supposed to prove? Sure, there are other systems by which to measure acids, but you haven't put forth anything specific, and you haven't provided any numbers. Sure, the acids' ranksing may be different using other measurements under other conditions, but without actual values to back that up, why should we believe it? Nope, the burden of proof rests on the side of the affirmative in any arguement, and if you truly believe you're right, then you'll have to give some hard evidense to back yourself if you want to convince people.
Now, moving on to bigger, better, and more practical things, like taking advantage of this new information you've given us. I think its important not to limit yourself with the idea of TSP as your only source of OTC phosphoric acid, especially due to its limited availability in many parts of the world. We must always "think outside of the box". Phosphoric acid itself is cheap and plentiful; its used as a food preservative, as well as a cleaning agent in the dairy industry. The local farm supply places sell phosphoric acid and polyphsophoric acid by the gallon, and its cheap. Buying it this way certainly beats trying to liberate it from a salt, that's for sure!
Still, if you don't have that available to you (which may be the case if you live in a non-dairy part of the world, like the modern urban jungle), you can always go the fertilizer route. Again, at many local farm supply places, a person can buy calcium hydrogen triphosphate and other related salts in big, huge sacks. This is where almost all phosphorous that is mined in the world ends up.
I have to say, this new HI/HBr preparative procedure is quite exciting. Do you have any experimental details available, or know where to find them? Somewhere in there, I imagine there's a solvent of some sort being used to whet the reagents, but what?
Anxiously awaiting more details,
- Smiley_Boy
(Hive Bee)
04-30-01 15:05
No 188191
"So at this point, we still have no procedure set out that we can point at and say: this is what everybody should use if gaseous HBr is what they want to make"
I guess that the DMSO method is the safest way to go, but that kinda sucks for cheap bastards like me, because 1 gallon of DMSO + shipping costs about $45. Oh well, at least there's no fucking haz-mat fee!
Here are some excuses to buy trisodium phosphate:
http://vm.cfsan.fda.gov/~dms/prodguid.ht
"Ozone has been used to sanitize wash and flume water in packinghouse operations. Ultraviolet radiation may also be used to disinfect processing water. Chlorine dioxide, trisodium phosphate, and organic acids (such as lactic and acetic acids) have been studied for use as antimicrobial agents in produce wash water, although more research needs to be done. Operators should consider options for water sanitation most appropriate for their individual operations."
Check out Custom Building Products [url]http://www.custombuildingproducts.c
Other uses:
Photographic Beveloper Ingredient
Denture Cleaner Formulations
Emulsifier And Neutralizer For Food
I'm going to help all of you cleanse this diseased planet.
(Stoni's sexual toy)
04-30-01 15:27
No 188198
> I guess that the DMSO method is the safest way to go, but
> that kinda sucks for cheap bastards like me, because 1
> gallon of DMSO + shipping costs about $45. Oh well, at
> least there's no fucking haz-mat fee!
Check the serious chemistry board. A few months ago I posted a much better way to bromosafrole there.
(Hive Addict)
04-30-01 15:48
No 188200
Smiley
I am surprised by the lack of interest too, but who knows?
You want a procedure?
Well you should look at "THE MAN's Site" more often.
http://rhodium.lycaeum.org/chemistry/hyd
Thanks Again Rhodium
Do Your Part To Win The War
(Hive Bee)
04-30-01 17:27
No 188218
couldn't HBr gas be produced from an aqueous solution if the aqueous solution were saturated with HBr at extremely cold temperatures, and then heated to just below its boiling point? I believe that HBr, as with most other haloacids, has a higher saturation concentration at lower temperatures than it does at higher temperatures.
If pacman influenced us, we'd glide around dark rooms eating pills and listen to repetitive music.
(Hive Bee)
04-30-01 17:53
No 188229
(Rated as: excellent)
For those who are interested in knowing the time tested methods from "Inorganic Laboratory Preparations":
Hydrobromic Acid
Of the six methods given here, the first three may be used for the production of gaseous hydrogen bromide as well as for aqueous solutions of the gas; IV, V, and VI can be employed only for making the constant-boiling acid.
(I)
H2 + Br2 --> 2HBr
The following apparatus is assembled in order:
1. A gas-washing bottle filled with water.
2. A distilling flask filled with 50 ml of bromine cooled in ice with the inlet tube leading almost to the bottom of the flask.
3. A Pyrex tube, 50 cm long, packed with about 80 cm of activated charcoal which is held in place with glass wool plugs.
4. A U-tube filled with glass beads or porcelain chips coated with moist red phosphorus.
5. Two wash bottles in series filled with 100ml and 50ml of water, respectively; if constant-boiling acid is desired, the second bottle should contain 100ml of water. Both bottles are surrounded by an ice-salt bath. The reaction train is set up in the hood.
A steady flow of hydrogen is started through the apparatus to displace the air. This operation requires about thirty minutes, during which time the bromine is kept in the cooling bath.
The furnace is now slowly warmed to 350-375' C and the flow of hydrogen is increased to a point where the bubbles are just too rapid to count. A bath of water at 40-45' C is now placed under the vessel containing the bromine; under
these conditions, conversion to hydrogen bromide is complete in about 20 minutes. No vapors of bromine should be visible at the outlet of the reaction tube; otherwise the bromine must be cooled somewhat in water.
At the end of the experiment the two wash bottles are removed and the hydrobromic acid absorbed is determined from the gain in weight; if the smaller volume of water was used, the concentration of acid should be 60-65% by weight. If constant-boiling acid is desjred, the solution should be distilled and the fraction boiling at 122-127' C collected as 47-48% hydrobromic acid. A rapid method for determining the concentration of the solution produced is by a rough determination of specific gravity. 65%, 1.78; 60%, 1.68; 55%, 1.60; 50%, 1.52; 45%, 1.44.
(II)
2P + 3Br2 --> 3HBr + H3PO4
In a distilling flask fitted with a dropping funnel are placed 25 g of clean sand and, over this, a mixture of 25g of red phosphorus and l00 g of sand. The mass is moistened with 40-45ml of water, and 50 ml of bromine are introduced into the funnel. A U-tube and absorption bottles as described under (I) are connected to the flask. The reaction flask is cooled in ice while the bromine is added dropwise at a very slow rate; the phosphorus may glow with each addition of halogen. In order to avoid a suck-back of the water in the absorption flasks, it is advisable to place an empty safety trap between the U-tube and the water traps. As the reaction proceeds, the evolution of gas is more readily controlled and the cooling bath may be removed. When all the bromine has been added, the distilling flask is gently warmed to drive off the remaining acid vapors. The working-up of the hydrobromic acid solutions is the same as previously described.
Yield in I and II is over 90% of theory
(III)
C10H12 + 4Br3 ---> 4HBr + C10H8Br4
If anhydrous hydrogen bromide is desired, the procedure is carried out in the absence of water, using dry reagents. The apparatus of method II is used.
Thirty-five grams of tetrahydronaphthalene are placed in the flask with either 150 or 200ml of water, depending on the desired concentration of the acid. At first the flask is cooled in ice while 50ml of bromine are slowly added dropwise; about one gram of iron filings catalyzes the bromination. As the reaction proceeds, the flask may be allowed to warm up to room temperature. After all the bromine has been added the flask should be shaken for some time; the aqueous layer should be colorless. The acid layer is then separated from the organic material and worked up as in I.
Yield about 90%
(IV)
H2SO4 + KBr ---> HBr + KHSO4
A mixture of 120g of potassium bromide and 200ml of water is cooled in ice while 90ml of concentrated sulfuric acid is slowly added. The temperature must not rise over 75' C during this addition; otherwise free bromine may be formed, causing a loss in yield. The reaction mixture is cooled to room temperature and the potassium bisulfate is filtered off by suction through a fritted funnel or a hardened filter paper. The filtrate is then fractionated and the material boiling from 122-127' C is collected as constant-boiling acid.
Yield = 85%
In all cases where a mixture of sulfuric and hydrobromic acids is obtained, a redistillation is necessary to remove about 0.01% of sulfate in the first fractionation; only the acid with a steady boiling point is retained. This operation entails a loss of about 15% in yield.
(V)
Br2 + SO2 + 2H2O --> 2HBr + H2SO4
Fifty milliliters of bromine are covered with 200ml of water and sulfur dioxide is passed into the mixture, under the hood, until a straw-colored liquid results. Fractionation yields about 300g of 47-48 % acid, which is an almost theoretical yield.
As this reaction proceeds, the bromine dissolves in the hydrobromic acid that is formed, yielding a homogeneous liquid into which the sulfur dioxide may be more rapidly introduced.
HBr+Br2 <==> HBr2
(VI)
2S + Br2 --> S2Br3
S2Br3 + 5Br2 +8H2O -->12HBr + 2H2SO4
One hundred and fifty grams of bromine are weighed into a glass-stoppered bottle in the hood and l0g of powdered sulfur are quickly introduced. The bottle is then agitated and the sulfur rapidly dissolves to yield a red oily liquid.
Two hundred grams of ice are placed in a 500ml glass-stoppered bottle and the vessel is immersed in ice. About one-third of the sulfur-bromine mixture is added; over the course of about one hour the red oil disappears. Cooling is maintained throughout the hydrolysis. The second third of the sulfur-bromine compound is now added, followed by the last portion about 30 minutes later. When all the material has dissolved and reacted, a pale yellow liquid remains which is fractionally distilled as usual; b.p. 122-127' C.
Yield about 300g of acid
Hydrobromic acid may be kept colorless for long periods of time by storage in a dark bottle in the refrigerator.
References:
(I) 1. I, vol. 1:152.
(II) 2. FILETI AND CROSA, Gazz. chim. ital., 21:64 (1891); B:71
(III)3. I, vol. 1:151; footnote, p. 152.
(IV) 4. I, vol. 1:155.
(V) 5. Organic Syntheses, Collective Vol. 1, p. 23, Wiley, 1936.
(VI) 6. FARKAS et oL, J. Soc. Chem. Ind., 66:116 (1947).
7. P:464.
(Hive Bee)
04-30-01 20:41
No 188266
Just to update on my ghetto experiment, oil has passed the foamy phase and is now back to dark colored oil/ no foam. The oil layer isn't being absorbded as quickly as I'd hoped, however I've been quite lazy and left it off the swirler for most of Sun. and Mon. The oil is brown / red, but not dark, still fully transparent. The HBr layer (more appropriately the ion soup layer) is cloudy white (started off clear).
I'm convinced a reaction with 48% HBr will work (references are numerous), although the purity and concentration of mine might cause my attempt to fail.
blah blah blah something clever blah blah blah
(Hive Bee)
05-01-01 08:53
No 188367
Foxy2,
Thanks for bringing that reference on Rhodium's page to my attention. Curiouser and curiouser. There are a couple peculiar things about the procedure as it is written. The first thing that caught my attention was that there's no reference; knowing where this came from would certainly be helpful (but beggars can't be choosers, I guess.) The second thing that I thought was strange is that there's no solvent, and though the reaction is run at 60 C, sodium dihydrogen phosphate has a mp of 95, meaning that as the phosphoric acid is used up, there'd be a mess of crystals, and reaction would have a difficult time going to completion, though maybe the mixture of salts causes a lowering in the melting point. But the thing that really made me wonder was the fact that they recommend using either 100 g NaI or KI, even though there is a considerable difference in the molar mass of these two salts, meaning a fairly large difference in the amount of final product.
This really has caught my attention. I'm going to do a little searching on my own, and see what I can find as far as where this idea originally came from (or at least, where published experimental details of this can be found.) There's a lot of ground to cover here, so I think it'll take a little time...
(Hive Bee)
05-01-01 13:30
No 188415
One reference you should check out is Ber. 23, 1642 (1890).
(Hive Bee)
05-01-01 14:35
No 188426
R.e. the lack of interest: I knew about the phosphoric acid + NaBr stuff long ago, I just tried to work around it cuz phosphoric wasn't easy to get. I found some TSP today, kudos to foxy for shownin me that one, I think I'll be making my own phosphoric now.
Hate to be a pest, but does the lack of comments on the experiment I have in progress mean that people don't know?
blah blah blah something clever blah blah blah
(Hive Bee)
05-01-01 15:31
No 188437
It turns out that the reaction of bromine with tetrahydronapthalene producing hydrogen bromide gas is an example of bromine reacting with many other hydrocarbons such as benzene, napthalene, anthracene or paraffin, as found in Anleitung zur Darstellung chemischer Praeparate by H. Erdmann (1890):
Pour 100 g of dry benzene into a flaks containing a few grams of anhydrous ferrous bromide, or fine iron powder, or aluminum powder. Run 135 cc of bromine very gradually into the flaks be means of separating funnel with the tube drawn out into a fine point. The flask should be put into cold water to prevent bromine or benzene from distilling over. When about half the bromine has been added, the reaction runs so quietly that the cooling is no longer necessary. The reaction is: C6H6 + 2Br2 --> C6H4Br2 + 2 HBr. To scrub the gas from the benzene and bromine vapors, pass the gas through a large U-tube, one leg which is filled with ferric bromide and the other with anthracene.
If one were to double the amount of benzene, one would have the same reaction for producing bromobenzene that is in Vogel's, which obviously produces hydrogen bromide gas along with bromobenzene.
As far the experiment, good luck, SWIM never had any with this route. If SWIM ever tries again, it will be using dry HBr gas in DCM as Osmium suggests.
(Hive Bee)
05-02-01 09:52
No 188648
The only conclusion that I ever came to about the HBr/Safrole production of bromosafrole was that it needed to be done at low temperatures, room temperature being the ceiling for this one.
The higher the temp. the greater the ether fission; the lower the temp. the slower the bromination of the double bond...
You get the point. I also don't beleive that the HBr method gets wonderful yields, I venture a guess of 75% tops...
(Stranger)
05-08-01 19:28
No 192818
SWIM think this is the best bromo-addition method SWIM have seen:
(OCRed from J. Org. Chem. 1980, 45, 3527-3529)
Addition of Hydrohalogenic Acids to alkenes in Aqueous-Organic, 2-phase systems in
the presence of Catalytic amounts of onium Salts.
Experimental Section
The general procedure for the preparation of 2-bromododecane is as follows. A mixture of 16.8 g of 1-docecene (0.1 mol), 55.5 mL of 48% hydrobromic acid (0.5 mol), and 5.1 g of hexadecyltributylphosphonium bromide (0.01 mol) is heated at 115 °C (bath temperature) with magnetic stirring for 2 h. After this time, NMR analysis shows a 94% conversion into 2-bromododecane. The organic layer is separated, the aqueous phase is extracted with dichloromethane, and the solvent is evaporated. The resulting oil is distilled to give 21.4 g (86.0%) of pure 2-bromododecane: by 125-126 °C (9 mm); n22 D 1.4594 [lit .5 by 125-130 °C (10 mm); n2lD 1.4600]. By treatment of the distillation residue with petroleum ether 4.8 g (94.0%) of phosphonium bromide [mp 52-54 °C (lit.' mp 54 °C)] is recovered, which can be reused without further purification.
SWIM is sure other PTCs can also be tried.
(Chief Bee)
05-09-01 05:21
No 192926
Yes, this procedure has been tried on safrole (see halosafrole.txt on my page) with Aliquat 336, and was found to work satisfactorily with 37% HCl, but not with 48% HBr, in the latter case the methylenedioxy bridge was cleaved.
http://rhodium.lycaeum.org