element109 (Hive Bee)
04-07-02 22:38
No 293803
      in situ HBr in acetic acid  Bookmark   

If you make in situ HBr in AcOH by reacting KBr and H2SO4, with a small excess of KBr of course, dissolve your olefin in there, 1mol olefin : 2mol HBr, this should brominate it, no?
I'm asking this because I found some contradictionary info about a HBr/AcOH mix cleaving the ether bond. Surely this happens only under increased temperatures?

e109
 
 
 
 
    Rhodium
(Chief Bee)
04-07-02 22:59
No 293817
      The problem is that HBr cannot be generated by ...  Bookmark   

The problem is that HBr cannot be generated by KBr/H2SO4 satisfactorily, some Br2 is formed. UTFSE on the reaction of dillapiole with HBr to find a good method. The Uncle Fester method (found at my page) using HBr dehydrated with dry HCl gas also works.
 
 
 
 
    PolytheneSam
(Master Searcher)
04-07-02 23:19
No 293827
      phosphoric acid  Bookmark   

How about phosphoric acid and KBr?  If you don't have phosphoric acid maybe you could make it in situ using calcium phosphate and sulfuric acid.

http://www.geocities.com/dritte123/PSPF.html
The hardest thing to explain is the obvious
 
 
 
 
    element109
(Hive Bee)
04-07-02 23:19
No 293828
      don't find it on TFSE  Bookmark   

Yes, I noticed that the solution is coloured yellow. Perhaps H3PO4 would be better then?

I did a run on TFSE on dillapiole but didn't found it.




e109
 
 
 
 
    Rhodium
(Chief Bee)
04-07-02 23:54
No 293842
      bromosafrole  Bookmark   

This thread; Post 22772 (Osmium: "Bromosafrole breakthrough?", Serious Chemistry)
 
 
 
 
    ChemicalSolution
(Hive Bee)
04-08-02 03:38
No 293935
      Bromination  Bookmark   

The DMSO/KBr method is, for sure, easier.. But how do the yields compare?

Has anybee distilled bromosafrole before???  details???
 
 
 
 
    hsark
(Stranger)
04-10-02 07:37
No 294894
      bromo distillation  Bookmark   

Yes lots and lots of times. The problem is in the end of the distllation you tend to get a volcano of black ash and smoke even if your careful. Ive been wanting to say this for a long while the 33% HBr in AA is the best to use. You can get 90 to 95% yields in 12 to 16 hours. Even though i was told 24. and you can just leave it in the freezer. although an ice chest works just fine.(with lots of ice.)when you distill it just be ready to disconnect it and have something to dump it in. And whatever you do save whats in the recieving side.wink
 
 
 
 
    Rhodium
(Chief Bee)
04-10-02 07:42
No 294898
      VERY Interested!  Bookmark   

hsark: Tell us more! How did you prepare the HBr/AA (is that Ac2O or HOAc?), what was the distillation temperature and pressure, properties of the distilled bromosafrole etc?
 
 
 
 
    hsark
(Stranger)
04-10-02 08:03
No 294914
      sorry you asked for more detail  Bookmark   

Manly i used to buy the 33% in AA from a chem suply. But i also used to buy the anh.HBr in cylinders and would make the solution myself. Bolth worked great. The main problem is i dont know how easy it is to get now for some. I dont have that problem. At around 20 torr. The bromo would start distill at 175 to 185. and would continue to rise slowly until it reached 212. at 212 decomposition. i generally  would stop at 205 but some times it decomposes even if your careful. i suggest be prepared and check for vac. leaks very carefully. it is generaly a reddish-brown transparent very nice, sweat smelling oil.  
 
 
 
 
    Rhodium
(Chief Bee)
04-10-02 10:20
No 294948
      Q/A  Bookmark   

Sweat- or sweet-smelling? I guess the latter. Finally, what proportions of HBr to safrole did you use?
 
 
 
 
    hsark
(Stranger)
04-10-02 21:24
No 295093
      bromo safrole  Bookmark   

Thats sweet. unless you think sweat is very nice wink. J/J the proportions were 1L 33% HBr in acetic acid to 450ml safrole. 
 
 
 
 
    otto
(Hive Bee)
04-11-02 00:30
No 295196
      further reaction  Bookmark   

hi hsark,

your results look very promising. what about the amination step? did you ever run it? otto was very sad when some alpha-methoxy-beta-bromophenylpropane didnt react in methanolic NH3 @110C for 16 hours (pressure tube).

otto
 
 
 
 
    Ritter
(Master Whacker)
04-11-02 02:10
No 295247
      ash volcano  Bookmark   

I've distilled quite a bit of bromosaf myself, and can tell you that a stronger vacuum will prevent that rapid charcoal-decomposition-volcano from occurring.  The decomposition is occuring because the still pot is getting WAY too hot.  When you only have a few ml's left in the still pot (about 50), cool it down and transfer the remaining liquid to a smaller 100ml flask.  This should allow distillation of the last traces of bromosaf without a problem. 

That charcoal volcano really sucks, I learned about that the hard way.  It actually shot all the way through my vacuum jacketed vigreux and into the condensor and ruined the $350 stillmad
 
 
 
 
    hsark
(Stranger)
04-11-02 04:42
No 295314
      amination  Bookmark   

I used to use the "pipe bomb" method for the reaction buy bubling  NH3 in to methanol. Then moved to isopropanol. It seemed to work better. I would run the reaction at 130 deg C for 3 hours. Mybe you cooked it to long ,but im not sure. a,but 110 worked when i didnt pay attention one time. I am now trying to reasearch better methods because the "pipe bomb" yields are just to low. I just finished the alaquat 336 and sncl method and im not real happy with it but i didnt distill the azide so its probably my own fault.But it wasstill beter than the "pipe bomb".
     
Thanks for the info herr Ritter on the over heating. And i have someone looking for the info you gave me the other day. But where im at i dont think i have access to it. I tried to search on the web but all the journals require membership i dont have. Or i just dont know how to do it. Can you help?      frown
 
 
 
 
    element109
(Hive Bee)
04-11-02 16:12
No 295481
      From Post No. 23995: reaction of o-allylphenols ...  Bookmark   

From Post No. 23995:

reaction of o-allylphenols (12,15) with HBr-AcOH
      aqueous Hbr (48% .2ml) was added to a solution of the phenol 12 (100mg)
in gl. AcHO (1ml) till the whole mixture became turbid.  The mixture was
warmed on a water bathe for 30-45 min at 50-60 c., diluted with water (10 ml)
and fractionated into phenolic and neutral portions. "

It cleaved the MD bond with light heating, but when kept cool, on the ice-bath, this should be of no concern.

45 saf : 100 33% HBr/AcOH and distilling with high vacuum;
followed by Finkelstein reaction (NaI in acetone) and then methylamine or a Gabriel synth, or even Delepine but I ain't going to mess around with the pipe-bomb, 'cause yields are just too low.



e109
 
 
 
 
    PrimoPyro
(Sector G)
04-11-02 16:24
No 295484
      NaI in Acetone?  Bookmark   

You do the Finkelstein reaction in acetone?

But sodium iodide bonds with ketones forming large molecular weight insoluble adduct precipitates. This is very peculiar to me.

                                                   PrimoPyro

Vivent Longtemps La Ruche!
 
 
 
 
    element109
(Hive Bee)
04-11-02 16:46
No 295492
      Huh? Isn't it always performed in acetone?  Bookmark   

Huh? Isn't it always performed in acetone? I haven't performed it myself, but I am 99.95% sure that the reaction medium is acetone.

I'll look up the original article.


e109
 
 
 
 
    Rhodium
(Chief Bee)
04-11-02 19:28
No 295523
      Finkelstein  Bookmark   

The Finkelstein reaction is always done in acetone, I guess the acetone/NaI complex is soluble in acetone, or that it does not form with low molecular weight ketones. I have wondered about that myself, PP.
 
 
 
 
    element109
(Hive Bee)
04-11-02 19:47
No 295531
      NaI  Bookmark   

yes, I remember NaI was being suggested as an alternative for NaHSO3 for MDP2P purification


e109
 
 
 
 
    PrimoPyro
(Sector G)
04-11-02 20:14
No 295549
      Must Be Soluble  Bookmark   

I know it bonds with acetone. There is a reference on your site, that cites Vogel as the original reference, and Vogel gives the example as the purification of acetone by crystallization of the adduct of the ketone and sodium iodide, followed by decomposing the adduct with heat.

I would think that for the crystallization, perhaps that is why the ketone is solvated, rather than NaI being added to the crude ketone itself.

                                                    PrimoPyro

Vivent Longtemps La Ruche!
 
 
 
 
    lugh
(Moderator)
04-12-02 03:11
No 295745
      Not Necessarily  Bookmark   

Post 205087 (lugh: "Re: CH2Cl2 to CH2I2", Chemistry Discourse)
 
 
 
 
    Rhodium
(Chief Bee)
04-12-02 03:33
No 295757
      And an improved method from JCS can be found at ...  Bookmark   

And an improved method from JCS can be found at ../rhodium /ch2i2.html
 
 
 
 
    hsark
(Stranger)
04-12-02 09:48
No 295941
      Yields for bromo to mda  Bookmark   

I thank you for the info on the finkelstien and delpine. But i have carried out these reactions and failed with the delpine. Im going to try them again soon though. my question though was about a post that Ritter mentioned.""Improved Method for the Synthesis of Alkyl Azides" P.238 Vol 22, 1957.  Look in all the major old journals (JACS,JCS,JOC) and you'll surely find it in no time."I was hoping someone could point me in the right direction. Its not the bromosafrole thats a problem. Its getting it to mda with respectable yields. The bromo/azide/mda reactions with alaquat 336 without distilling the azide and then SnCl reduction  yielded a 40.96%. Im going to distillthe azide next time.

It sure would be great to see the write up you mentioned herr Ritter.   

Someone once told me if you dont like it move.So i did.
 
 
 
 
    endo1
(Stranger)
06-16-02 11:01
No 322022
      HBr in GAA is great / Ash volcano sucks  Bookmark   

_____________________ [a]
J/J the proportions were 1L 33% HBr in acetic acid to 450ml safrole.
____________________ [a]

SW uses less HBr (500ml to 300ml sas) but stirring is necessary. HBr  in GAA chilled down in freezer over night and sas cooled as much as possible without freezing before adding both to a gem jar with concave bottom sealed tightly(SW had problems with flat bottom flasks due to friction of the stir bar). Place jar on magnetic stirrer and place whole thing in deep freeze for 48 hours! Quenched on ice and washed as usuall. SW gets 90%+ yields. SW thinks that 24 hours is probably sufficient but he leaves it for 48 because of his schedule.

SW finds that occasionally the "black tar" near the end of the still during purification erupts in to the ash volcano mentioned earlier in the thread. The more "black tar" or "darkness" the more likely the eruption. Sometimes its much more like an explosion than a volcano. SW uses good asperator with high water pressure and cold mountain water. He starts collecting his bromo at about 145 and collects till about 162 (where the flask is almost empty and distilate begins to darken a tad). Some things SW thinks might minimize the "black tar" are:
-wash it while its still cold and wash it well
-keep it in the freezer untill ready to distill it (and after too)
-use vacuum for entire distillation including solvent stripping. and use best vacuum possible for collecting bromosafrole as the distillate. (check for leaks etc.)
-dont run the water anywhere else in the building! this can change the water pressure which may cause a loss of vacuum.

Basically he keeps it as cold as possible even during and after its been washed etc. Since SW has started doing this he has had no explosions! (His walls and cieling thank him... so does his wife!) All of SW's explosions can be tributed to SW leaving the bromo at room temp by accident and forgetting about it after washing it or to accidently flushing the toilette at the wrong time.