12-31-03 17:42
No 480063
I was just wondering what are people's preferred method of safrole isomerization and the conversion percentage.
Have tried both the NaOH/CaO method as well as the NaOH only with vacuum. Safrole was good. Both distilled AND frozen.
Does it really seem to be sensitive to the batch sizes? Seems a pain to do it in 100 ml batches. With the NaOH/CaO method using 500ml safrole at a time and refluxed for about 4 hours the amount of isosafrole produced and recovered is usually about 55-65%. Seems a bit low to me.
With the vacuum method it doesn't seem to be much better but friend did not calculate as accurately. Also leaving the pump on overnight ain't really good for the pumps.
Anybody else care to comment on their experience and conversion efficiency?
(Stranger)
12-31-03 18:08
No 480067
Perhaps I should mention that of course I have UTFSE for the "published" conversion yields and I am only looking for anyone to comment on their personal experiences with yields and how sensitive the methods are to 'scale up'.
The vacuum only method does not mention yields. When theoretically working with many liters, 100ml conversions are a pain. Still fun, of course.
Safrole ain't as easy to find anymore so every little bit of insight helps I would think.
Or so I've been told.
(Hive Addict)
12-31-03 22:52
No 480081
(Rated as: good read)
Dunno about personel experiences, but I can recite some info that has been posted here before that you would have found if indeed you did UTFSE!!!!!!
First off, all methods are fine (cept CaO, messy and useless) and 55% yields are pathetic. 166grams of freshly distilled safrole with 3.3g of KOH should be heated to 130-150c for 4-6 hours. Many people have noticed that 150c for five hours provides 159grams of isosafrole from 166g safrole. The beginning of the reaction should be done under strong vacuum. Once the KOH is powdered in a mortar and added to the safrole you should setup for distillation and turn on vacuum. I would suggest something between .5 and 3torr. Once the contents of the flask stop bubbling, continue to draw a vacuum on the apparatus while heating, slowly letting air into the vacuum pump as the temp rises to keep the safrole from boiling. Once you reach 100c (1-2hrs) you can shut down the vacuum pump. It should be noted that you should not bleed air in through the still or apparatus, but through the pump's head itself. Before shutting off vacuum you should close your stopcock inline to your vacuum adaptor to keep air out. Once the mix has been at 150c for at least four hours you can count 130c, so from 130c six to eight hours. The slow temp climb will alow 2hrs from 130c to 150c then four from there. Once the reaction is complete turn off hotplate lower your jack stand and put a fan on the apparatus. Cool to at least 40c and then raise you hotplate back and start heating again with vacuum on. Distill off your iso at 75c with a bath temp of 85-92c. Ruthenium, Rhodium, Osmium metal salts provide the fastest cleanest isomerization of many allylbenzenes. KOH isomerization can be done at 120-130c but require about eight hours. Only running it 130c for four hours provides 80ml from 100ml safrole, but is very clean leaving only amber crystals and no tar allowing multiple batchs back to back with the same KOH residue.
Scaling has no effect on yields. It only effects ease of handling. The full vacuum reflux on large ammounts tend to bump alot. This is hard to eliminate easily, but can be done. You can either use a capilary instead of stirring, bump trap inline from flask to column, and a vertical column to the distilling adaptor. This way if it bumps it won't shoot into the condensor. It would be better to just not reflux under vacuum. Refluxing is not nessecary. Just run a vacuum untill about 20-30c past the bp of water then close off the apparatus using an inline stopcock and shut off vacuum. As long as you can get the temp around 130-180c without it boiling you'll be fine.
(Stranger)
01-01-04 08:55
No 480121
I'll dream that method next since, I agree, 55% yield is pathetic and safrole is pretty dear these days. If, with the vacuum only method, I can approach 95% conversion that is the way to go since the only scale up problems seem to be with the bumping.
(Hive Bee)
01-03-04 06:29
No 480239
Wonder why cub always fail with these super easy vac reflux methods.Only 230C and 3 hours worked him with 55% yield,conversion was 100% though.Will pioneer pentacarbonyliron methods soon and see if these produce better yields.
(Stranger)
01-03-04 06:33
No 480241
Yea, I was pretty sure it wasn't just me. Tried several different methods but always got shitty yields. That's why I was asking for anybody else's personal yield experience because I'm tired of reading methods that claim certain yields but never getting them. And I'm not just talking about isomerization either. I can't even begin to list the various variations in methods that are published somewhere that for all intents and purposes just don't work. Or work very poorly. It gets to the point where you know some people are writing things up that they haven't tried but should "theoretically" work. I'm pretty tired of it.
(Hive Addict)
01-04-04 06:43
No 480361
(Rated as: good read)
I can assure you that the method I posted is from a very credible source and is very accurate. It was derrived from many a discussion on full vacuum reflux methods to only using vacuum at the initial part of reaction. After reading the patent for RuCl3 isomerization and the vacuum reflux by Osmium it was decided that only a few hours were needed.
"at approximately 120°C. The reflux was continued overnight, the vacuum source disconnected, and the reflux condenser was replaced by a fractional distillation setup with a vigreux column and the isosafrole was distilled, again with good magnetic stirring. Refraction index measurements shows the reaction to be mostly completed after approximately 3 hours"
"was stirred at 130°C for 4h. The black oil was distilled at the water pump to give 45g of safrole at 110-117°C, and the bulk of the oil distilled at 118-121°C yielding 360g of crystal clear isosafrole (90% yield based on the reacted safrole)."
../rhodium /isomeri
Failure is most likely your technique of from your oil.
Are you distilling your sassy? Have you done anything to confirm the purity of the supposed safrole fraction? How can you be sure your sassy doesn't contain adulturants? I know of a few bees that have been getting tainted oil from the few sources that still sell it.
3hrs@230c?? Should be more like fifteen minutes!
"Isomerization of distilled 1-alkene with 1% KOH can be done, according to SWIM with >90% yields in under thirty minutes at 243°C.
Experimental: Dissolve using heat and good stirring 1 gram of KOH in ethanol of methanol. Once dissolved, add 100 grams of distilled 1-alkene to mixture and increase heat to distill off the alcohol, which can be reused. Place thermometer in flask and continue to heat and stir until temperature reaches 243°C (it will hit 232°C first, linger awhile, but will soon ascend). Hold for 5 minutes, the turn off heat and let cool. Next, vacuum distill to get desired product."
../rhodium /oxone.e
Iron pentacarbonyl is toxic and expensive and I am unsure of its role in being reusable. I would suggest you buy some noble metal catalyst of some sort. Ruthenium seeming to be the easiest and cheapest to get at just about anywere. Prices for RuCl3 range from $55-165 dollars per five grams. And for what little is used it is quite economical seeing as it is reusable. Also smaller ammounts can be used with an increase of reaction times. The overall low conversion cited on rhodiums page under RuCl3, can be achieved with using only KOH. Using an expenisve catalyst to have 45g safrole forerun is quite ridiculous. You can achieve the same thing in the same 3-4 hours using 1.5%wt KOH catalyst.
Patent US4138411
../rhodium /isomeri
Post 350467 (sYnThOmAtIc: "Isomerization Problems", Chemistry Discourse)
I know that the person who has given me his info to post above doesn't like running reaction past completion, but rather under completion. He likes the confirmation of a first small fraction folowed by a brief second and a final major fraction. Takes some of the guess work and confirmation work out of the final processing.
There is very little misinformation on the hive, period. And what little there is is very obvious or has been posted or rated as such. You would know this if you tried a few of them. After all, most all the information here comes from legit and well respected sources of professional publishings. Often times a failure comes when an individual is unable to reproduce exact conditions because of lack of detailed information or some other circumstance.
Your failure in isomerizing safrole is not the fault of the hive. It is a very simple process that can be done very easily and with high yields when you know what your doing. Isomerization of safrole for what seems to be your intended use is ILLEGAL anyways and you should not be making personal coments about it anyway. You should damn sure not be asking other bees to do the same. Take it all with a grain of salt! I am not proficient in chemistry like our master bee Rhodium, but I can see that refuxing vanillin with dimethyl sulfate produces a di-methyl derrivative from the 3-methyl, 4-hydroxyl aldehyde to make 3,4-dimethoxy aldehyde... It's very simple as is your selected reaction. It is not our problem that you don't take the time to learn this method correctly before proceeding.
SO QUIT BITCHING!! Nothing is perfect. Can't always believe what you read/hear. Blah, blah, blah, etc... That being said, good luck with your next go at it
(Hive Bee)
01-04-04 11:38
No 480381
What magic temperature this 243 C is?It's not a bp of safrole nor isosafrole.Even lower-boiling isomer of isosafrole boils higher than 243 C.Iron pentacarbonyl is toxic but not expensive and only very little is needed for very high-yielding isomerization.Probably not reusable but it's not problem.Safrole used where cub failed was reasonably pure(3 x freezed and d20 1.095-6).
That one with CaO also worked once for cub with 80% yield but same yield couldn't be achieved again for some reason.Will try refluxing with 1-2% KOH at atmospheric pressure for half an hour when new safrole arrives.
(Hive Addict)
01-04-04 12:15
No 480385
The temp of the bath is set higher than bp to ensure initiation of reaction and to allow for measurable temp climb. Once all the safrole has converted to isosafrole the temperature will climb as there is no lower BP oil to take a reading of. At such high temperatures conversion rate is quick and will continue to react untill below 80c. Once a temp climb is noticed then a a nearly full conversion of cis safrole has occured taking about fifteen minutes. It will take another ten to twenty minutes for the mix to cool sufficiently to stop reaction. During this time more trans isomer formation is influenced. If you were to wait intill the 255c temp for trans you will get alot of ruined iso. The iso will decompose into tar lowering your yield and wasting precous sassy.
Who ever pioneered and researched the method did many experiments and found a medium to where yield are maximized and undesired side-reactions are kept to a minimum. Called experimentation!!! I still don't think someone who can't manage to sucessfully achieve a decent yield from a very practical and easy method using only KOH should be handling and using the toxic iron pentacarbonyl! You should learn one before trying another! Aptmospheric reactions are hard to accomplish unless you are using silicone oil bath or haeting mantle. You end up some nasty tars as well though not alot when carried out in the proper time alotment. If you just do what I say and run a vacuum untill you have reached reaction temperatures and sht it down there is absolutely no water in the mix. My friends vacuum pump removes all traces of water at room temp anyway but sees no reason why not to continue to run vacuum untill 100c. When sassy boils at 55c then water has no chance of being in there at room temp and especially not at 100c. Even weaker vacuums will work as long as you run it until reaction temp. You should even need to reduce vacuum gradually during the temp rise to keep sassy from boiling and distilling over. Then only ting you need to do is distill and rinse your flask out with hot water and it's spik and span or us it for another batch.
BTW 242-245c is the boiling point of cis iosmer!! At least as far as I have ever known.
~234c ---safrole
~246c ---cis/isomer >-These are just close estimates
~253c ---trans/isomer
(Hive Bee)
01-04-04 12:47
No 480389
(Rated as: dangerous)
Cub has worked with various toxic chemicals like sodium cyanide(when making benzyl cyanide from benzyl chloride and he succeeded),he doesn't think pentacarbonyl is more toxic and like said before,quantities are small.Cub doesn't know why isomerizing safrole is difficult for him,he has had never problems with performic oxidations or borohydride reductions.He isn't blaming anyone,it just doesn't work for him.There's gotta a way to easily isomerize safrole in few hours at reasonable temps and it seems that pentacarbonyl route should be very viable.Pentacarbonyl is non-watched chemical and is quite common.When used carefully no problems should come.
(Chief Bee)
01-04-04 16:54
No 480418
RuCl3 is what you are looking for. Someone posted a 90% conversion in 4h at 130°C a while ago and it's included in my Safrole Isomerization Review (../rhodium /isomer
The Hive - Clandestine Chemists Without Borders
(Hive Bee)
01-04-04 18:14
No 480422
Iron pentacarbonyl is incredibly toxic, but is easy to make by exposing iron powder to carbon monoxide under pressure and at 120C, I believe. I posted a hypothetical synthesis a while ago that nobody commented on, probably because it was suicidal. I know MSDS's are usually pretty bad, but iron pentacarbonyl's is downright scary.
over and under, then back to the start
this sidewalk's bottom is the same as its top
(Hive Addict)
01-04-04 20:08
No 480433
Your starting to contradict yourself there buddy! Easy? Fe, CO underpressure at 120c =suicidal? Not sounding so easy anymore!
Yes, RuCl3 is far supperior and is actually quite inexpensive when you figure what your getting. Plus it is my experience from making isoeugenol that RuCl3 is also much easier to acquire/store. I would never handle iron pentacarbonyl for any reaction, especially not when something like KOH can be used with suitable results.
(Hive Bee)
01-04-04 22:26
No 480451
Oh, making it is the easy part, keeping it from exploding is the real trick.
And being able to efficiently isomerize 500ml of olefin without the benefit of a vacuum pump has its advantages. I tried the KOH trick without a pump once, and I regretted it terribly (this was before I learned about the mineral oil flask treatment).
over and under, then back to the start
this sidewalk's bottom is the same as its top
(Hive Addict)
01-05-04 01:08
No 480471
What is the mineral oil flask treatment?
Yeah doing this reaction with KOH and no aid from a vacuum at some point doesn't produce desirable effects. Unless you oven dry your glass and hydroxide, then freshly distill sassy at aptmospheric pressure, you will most likely not get good results from using KOH alone. The preparation is sort of tedious, but not complicated. I remember in the isomerization x2 success someone posted a request for a koh, no solvent, and no vacuum process. Has anybody ever tried the conventional preparation for an anhydrous reaction like described above? Might work?
Don't get me wrong I like RuCl3, but I haven't tried it with safrole. I just wouldn't run it for only 3-4 hours. I'd run it a bit longer to get a lil less forerun. As you will soon have spen two vacuum pupms worth of money on salt. What is so bad about using vacuum for a brief period of time? I have only used it with eugenol after many failed attempts at isomerizing it... You people think you got it bad with KOH and sassy, try making isoeugenol with >50% yields. Now that simply just sucks ass! Not to mention the ten fold ratio of alkali to olefin and high temps. I must have tried about five different methods before finally breaking down and getting some RuCl3 and using it, viola!
(Hive Addict)
01-05-04 01:22
No 480473
> viola!
viola is a musical instrument, like this one:
voilà! means something like "and done!", "so there!"
filter(lambda W : W not in 'ILLITERATE','BULLSHIT')
(Hive Bee)
01-05-04 01:50
No 480477
Iron pentacarbonyl is incredibly toxic, but is easy to make by exposing iron powder to carbon monoxide under pressure and at 120C, I believe. I posted a hypothetical synthesis a while ago that nobody commented on, probably because it was suicidal. I know MSDS's are usually pretty bad, but iron pentacarbonyl's is downright scary.
Pentacarbonyl should be bought not made(1 kg 300$ from Aldrich for example and with a kilo you can isomerize few hundred kgs of safrole).It's not practical to prepare it at home.
(Hive Addict)
01-05-04 04:19
No 480492
Could you not sense some sick humor there? It was not meant seriously! At least I don't think gruns was serious
If I wouldn't use it I damn sure wouldn't make it!
hypo--- I hope you meant your post was off topic not mine! And excuse me for not knowing how to use accent markings in the hive
01-05-04 04:22
(Rated as: off-topic)
01-05-04 05:03
(Rated as: off-topic)
(Stranger)
01-05-04 12:14
No 480554
I do appreciate the advice and it's good to see that it has created a dialog of some sort (even a viola picture!).
I'm sorry if you thought I was bitching. I certainly wasn't but maybe I was just whining a bit in hindsight due to being sober and sleepy perhaps. My mistake.
I'm beginning to think that a too-high cis concentration may be involved.
I truly do appreciate the feedback. Thanks.
(Hive Bee)
01-05-04 13:56
No 480585
Synthomatic: Washing the flask with mineral oil immediately after cooling from rearrangement and distillation will get rid of most of the black gunk. If you wash it with ANYTHING ELSE first, this trick will not work and that black gunk will stare at you with hatred in its little black gunky eyes until you scrape it off.
over and under, then back to the start
this sidewalk's bottom is the same as its top