Bibliographic Information

Hydrolysis of chlorinated styrene - a new route for the synthesis of
phenylacetic acid and a-ethoxyphenylacetic acid. Lanchow University,
Dep. Chem., Lanchow, Peop. Rep. China. Huaxue Xuebao (1976),
34(4), 295-300. CODEN: HHHPA4 ISSN: 0567-7351. Journal written in
Chinese. CAN 88:104848 AN 1978:104848 CAPLUS

Abstract

Chlorination of styrene in the presence of Bz2O2 at 100-10° gave 12
chlorinated products, which on alk. hydrolysis in alc. gave PhCH2CO2H,
PhCH(OEt)CO2H and BzOH in 56-63, 7 and 0.6% yield, resp. Chlorination of
PhEt gave similar products, and esterification of the crude acidic
products gave 53.4% PhCH2CO2Et. [Reaction proceeds through dehydrohalogenation of a,b,b trichloroethylbenzene to phenylchloroacetylene]

/discuss

Cross post.

After mulling over the problem of producing PAA in high yield from styrene, the following innovative procedure was hit upon, following the same chlorination theme.

It is based on the fact that styrene readily adds chlorine in the cold thru electrophilic addition across the double bond to yield mainly 1,2-styrene dichloride, and also the fact that this styrene dichloride readily undergoes dehydrohalogenation when stirred with aqueous alkali at room temperature, to yield another unsaturated compound, a-chlorostyrene. The key is that this chlorinated styrene can be chlorinated a second time, in the exact same way as the original styrene, to take up two chlorines across the double bond and become trichloroethylbenzene. If you've been paying attention, this is what the chinese papers say can be dehydrohalogenated to phenylacetic acid in 90%+ yields.

To sum up, the simple chlorination of styrene proceeds rapidly to yield dichlorostyrene. Better, the dehydrohalogenation of dichlorostyrene is extremely facile and proceeds in high yield.

According to J. Am. Chem. Soc., 1945, 67 (4), pp 518–520:

Quote

a-Chlorostyrene from styrene dichloride: To a solution of 99g (2.5 moles) of NaOH in 377 ml of EtOH and 124 ml of H2O was added over a 3/4 hr. period 333g (1.9 moles) of styrene dichloride. During the addition and for 4 hrs. thereafter, the mixture was stirred at 50-60C. It was then diluted with water and the product removed by extraction wih benzene. When the benzene solution was distilled, 234g (89%) of a-chlorostyrene was collected at 80-83C (21mm).

.
 From US2898381:

Quote

A slurry of 120 grams of p-nitrostyrene dichloride in 120 ml. of methanol and 250 ml. of 10% sodium hydroxide was warmed at 60° C. for one hour, cooled and filtered. A 100% yield (101 grams) of p-nitro-alphachlorostyrene having a melting point of 63° C. was obtained.

After the a-chlorostyrene is isolated, it is fed back into the chlorination step to yield trichloroethylbenzene in equally high yield. I dug up a reference for this, but it is mostly unexceptional; just to prove that it can be done. It consists of bubbling one mole of chlorine through one mole of styrene derivitive. This is then hydrolyzed in alcoholic NaOH under pressure to yield Na-PAA. Incidentally, this is performed under very similar conditions to the Willgerodt, so the fire extinguisher autoclave is the method of choice here, I am certain. 

Additional refs.:

Interesting patent whereby styrene is chlorinated with in-situ Cl generated by HCl and an oxidizer such as hypochlorite: http://www.google.com/patents/about?id=6VpoAAAAEBAJ

Additional information on the (hypo)chlorination of styrene: http://www.nrcresearchpress.com/doi/pdf/10.1139/v64-428

It is from the-collective.ws, Sedit. See my thread over there for more detailed information concerning the chinese patent. It doesn't really matter, anyway, because the reaction I am suggesting does away with the need for radical initiators, and relies on simple electrophilic chlorination in the cold. Perhaps I will post a diagram in the future if anyone still cannot follow what I am proposing.

I will have to search in the WD archives for I somehow remember that there was already something with styrene dichlorination and a chinese patent. It didn´t work out, as far as I remember there were several problems, one of the bigger ones being the fact that Styrene in all forms is permantly on the edge to polymersation just inhibited by some - yes inhibitor. Thats one reason a lot  of solvent is required and even then... Of course radical initiation is out of question 

It always made plastic...

But prove me wrong I like to see this working!
 
Reading the EU patent I made some observations. First, they keep it very broad in the description, 1mol to 100mol of X may be used preferably 2 to 50 and more of this bullshit. And they had heaps of examples. Looks they had to make up for some inconsistencies in the method. Next, in the reaction they used about 0,1mol substrate with 0,5l alcohol and 0,3l water plus something more, what tells us that for reacting 1mol one would need near to 10 LITERS. This makes it volumetrically uninteresting for practical use. But worse. Even in this highly diluted system they were not able to isolate the product. "Yield" and conversion were only measured by GC. Thats highly unusual, actually it´s a "no-go" filing a patent. At least once the amount of product which can be extracted has to be shown, for this claims to be a practical useful procedure. I suspect that there was product , but it was plasticized in a matrix of polymeres. This would go nicely d´accord  with the experiences made by freelancing experimenters when working on styrene - what looks so tempting but is such a bitch.

I still hope that I am wrong.

/ORG