Roser' obtained the amyl ester of benzoyl-formic acid from the acid chloride of mono-amyl oxalate, benzene and aluminum chloride. This preparation suggested the use of the acid chlorides of the mono-alkyl esters of the phthalic acids for the preparation of various keto acids. The isophthalic acid and the terephthalic acid were prepared by the oxidation of commercial xylene, which had been fractionated with a 15Ocm. column, by Professor Kenrick in this laboratory. It was found that the fraction

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... oiling at 138.2' to 138.4" gave the largest yield of terephthalic acid. Oxidation of the Xylene.-Fifty g. of xylene, b. p. 138.2' to 138.4", 5 liters of water and 30 g. of sodium hydroxide were heated to 90" in a 10-lLter can which had a tight-fitting cover containing openings for condenser, mechanical stirrer and thermometer. All the openings were made steam tight. To the mixture was added 300 g. of potassium permanganate in 4 equal portions at half-hour intervals. After 19 hours' heating a t 83" to 95" the solution was decolorized with methyl alcohol, cooled, filtered and the filtrate acidified. The precipitate dried at 110" weighed 60 8. Separation of the Acids.-This product was found to be practically free from phthalic acic! which is soluble 0.58 g. in 100 g. of water at 20". The isophthalic acid and terephthalic acid were separated by means of their barium salts. The solubility of barium terephthalate and barium isophthalate, determined by evaporating a saturated solution and drying the residue a t 200" for 8 hours, was found to be approximately 0 . 5 g. and 14.0 g. respectively in 100 g. of water at 20 ' . Fittig2 using this method boiled the acids with barium carbonate but this is not convenient when using large quantities. Sixty g. of the mixed acids was made into a paste with water and warmed with 125 cc. of conc. ammonia on a water-bath for 20 minutes; more water was then added to dissolve the ammonium salts, and the solution was boiled to expel the excess of ammonia. When nearly neutral, the volume was made up to 350 cc. and a hot solution of 40 g. of barium chloride in 70 cc. water added. After shaking for one hour and standing for 12 hours the barium terephthalate was filtered off, washed, and digested on a water-bath for 6 hours with 100 cc. of 1 5 % hydrochloric acid; yield Roser, B e y , 14, 910 (11381) ? Fittig, A n n , 153, 369 (1870).