SYNTHESIS OF PHENYLPYRUVIC ACID

•  Place 10.3g (0.05 mol) of a-acetamidocinnamic acid and 200 ml of 1 m hydrochloric acid in a 500-ml round-bottomed flask and boil the mixture steadily under reflux for 3 hours. 

• Remove a small quantity of green oil by rapidly filtering the hot reaction mixture through a small plug of cotton wool loosely inserted into the stem of a preheated glass filter funnel, cool the filtrate  to room temperature and leave it at °C for 48 hours. 

• Collect the crystalline product by filtration, wash it with a small quantity of ice-cold water and dry it in a vacuum desiccator over anhydrous calcium chloride and potassium hydroxide pellets. 

• The yield of phenylpyruvic acid, which is sufficiently pure for most purposes, is 4.4 g, m.p. 157 °C (decomp.). 

• A further 1.7g of product of comparable purity (total yield 74%) separates from the aqueous acidic filtrate when this is set aside at °C for about one week.