Phenylacetic Acid via the Willgerodt Reaction from Styrene

A mixture of styrene (104 g, 1.00 mole), sulfur (80g, 2.5 moles) and
morpholine (174 g) was refluxed two hours (internal temp rising to about
175°C). The cooled reaction mixture was taken up in chloroform (some sulfur
remained undissolved) and the chloroform solution was washed successively
with an equal volume of water, sufficient dilute hydrochloric acid to
remove the excess morpholine, and finally with an equal volume of water.
The solvent was removed under vacuum, and the residue of crude phenylthio-
acetmorpholide was refluxed for ten hours with 1200 ml of 50% (by weight)
sulfuric acid. The cooled hydrolysis mixture was extracted with three 500
ml portions of ether and the combined ethereal extract was washed with 100
ml of 12% caustic soda. The caustic wash was acidified with conc. HCl and
then extracted three times with 300 ml portions of ether. Removal of the
solvent from the combined ethereal extract gave 114g (84% yield) of nicely
crystalline phenylacetic acid, m.p. 72-74°C.

One run in which the original reaction mixture was concentrated under
vacuum on the steam cone and then hydrolyzed directly with 50% sulfuric
acid gave only a 59% yield of phenylacetic acid, m.p. 71-74°C.

