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Author: Subject: preparation of organic peroxy acids and epoxides help
ThatchemistKid
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[*] posted on 14-1-2011 at 11:53
preparation of organic peroxy acids and epoxides help


I have been searching for a suitable way to prepare peroxybenzoic acid (or some other organic peroxy acid for making styrene oxide via the Prilezhaev reaction) , but all I have found were articles that show its preparation from benzyl chloride and sodium peroxide.

An Improved Synthesis of Peroxybenzoic Acid was the title of the article in ACS

and there was also another synthesis described in orgsyn

http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv5...

that required 70 percent hydrogen peroxide.

my hydrogen peroxide is a 30 % solution and I have no sodium peroxide.

Now I have read of one more method peroxy acid synthesis for peracetic acid that involved mixing of hydrogen peroxide and glacial acetic acid into an aqueous solution containing a catalytic amount sulfuric acid and waiting for ten days for the equilibrium to favor more product. This preparation is basically a variation of the orgsyn one mentioned above.

What I am asking is, is it necessary for the reaction that I am attempting to have a concentrated solution of the peroxy acid or can a solution of hydrogen peroxide and benzoic acid or acetic acid work, on the basis that whatever small amount of peroxy acid present will be used up in the epoxidation pushing the equilibrium thereby forming more peroxy acid that is then used up and the cycle continues until the reaction goes to completion. (as in formation of the peroxy acid in-situ)

Also I am wondering about cross reaction with the free hydrogen peroxide. I am aware that hydrogen peroxide itself can be used to form epoxies but, I am not certain of the conditions for that reaction except that it is often used for the epoxidation of enones, which maybe a mechanistic hint.

any help would will be appreciated
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Nicodem
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[*] posted on 16-1-2011 at 10:28


Quote: Originally posted by ThatchemistKid  
I have been searching for a suitable way to prepare peroxybenzoic acid (or some other organic peroxy acid for making styrene oxide via the Prilezhaev reaction) , but all I have found were articles that show its preparation from benzyl chloride and sodium peroxide.

Peracids are not the best option when it comes to preparing styrene oxide which is prone to ring opening in acidic media (particularly the more acidic ones like performic acid or H2SO4 containing peracetic acid formulations). There are examples in the literature of m-chloroperbenzoic acid being used, but otherwise styrene oxide is best prepared using some of the epoxidation methods in neutral media (Oxone/acetone, H2O2/acetonitrile, t-BuOOH or H2O2 with metal catalysts, etc., or via the halohydrin formation/ring closure). There are literally hundreds of methods described in the literature. I went undiging my old home chemistry lab book to give you this alternative that uses a one-pot chlorohydrin preparation followed by cyclization. It is very simple and highly OTC-ish. The chlorohydrin preparation part is based on Synthesis 2003, 45–48. The cyclization part is trivial.

Styrene oxide: In a flask equiped with a thermometer was added 30 g of styrene (288 mmol), 240 mL acetone and 60 mL water.(1) While stirring on a cooling bath there was slowly added a solution of 24.4 g trichloroisocyanuric acid (TCCA, 100 mmol) in 100 mL acetone at such rate that the temperature never went above 30°C. This took about half an hour and after the first third of TCCA solution was added, cyanuric acid begun precipitating. The mixture was left stirring 45 more minutes and the unreacted TCCA quenched with the addition of 0.5 g Na2SO3. Five minutes later 50 mL of 10M aqueous NaOH (500 mmol) was slowly added drop-wise. The temperature rose from 25 to 32°C and two phases formed. The lower, minor one which was a white slurry and the upper acetone solution which was a clear liquid. The upper phase was separated by decantation after stirring for an additional 1:30 h. This was then washed with 50 mL brine.(2) The acetone was distilled off and the remaining mixture distilled under the vacuum of an aspirator (no distillation column was used). At about 50 °C water with a few drops of the product that steam distilled came over. Then at 100-140°C a colourless liquid came over (bp lit. 100-102 °C at 40 torr according to JACS, 77, 1738-1743; 194 °C at normal pressure). Some yellow gelatinous side product remained in the flask. The distillate was slightly denser than water (lit. 1.054 g/mL at 25 °C according to Sigma), clear, with a slightly sweet smell, without any residual styrene smell, and amounted to 25.15 g (73%). No additional analyses were performed. It was however used in further transformations (like alkylation of amines, etc.) giving expected products with the correct mp.

(1) Probably even less acetone could have been used without detrimental influence.

(2) The extract should have been further dried, because much water remained unextracted by brine and this later caused some minor problems during distillation.




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ThatchemistKid
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[*] posted on 16-1-2011 at 14:07


WOW! thank you so much for your help. Ill post results etc.. once i preform the experiment.
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