HIPPURIC

ACID (Gr. iazros,

See also:

• HORSE (a word common to Teutonic languages in such forms as hors, hros, ros; cf. the Ger. ross)

horse, ovpov, urine)  , benzoyl glycocoll or benzoyl amidoacetic acid, C9H9NO3 or C6H5CO NH•CH2•CO2H, an organic acid found in the urine of horses and other herbivorae . It is excreted when many aromatic compounds, such as benzoic acid and toluene, are taken internally . J. v . Liebig in 1829 showed that it differed from benzoic acid, and in 1839 determined its constitution, while in 18J3 V . Dessaignes (Ann . 87, p . 325) synthesized it by acting with benzoyl chloride on zinc glycocollide . It is also formed by heating benzoic anhydride with glycocoll (Th . Curtius, Ber., 1884, 17, p . 1662), and by heating benzamide with monochloracetic acid . It crystallizes in rhombic prisms which are readily soluble in hot water, melt at 187° C. and decompose at about 2400 C . It is readily hydrolysed by hot caustic alkalis to benzoic acid and glycocoll .

Nitrous acid converts it into benzoyl glycollic acid,

C6H,CO.O•CH2•CO2H . Its ethyl ester reacts with hydrazine to form hippuryl hydrazine, C6H5CO•NH•CH2•CO•NH•NH2, which was used by Curtius for the preparation of azoimide (q.v.) .