HYDANTOIN (glycolyl

See also:

• UREA, or CARBAMIDE, CO(NH2)2

urea), C3H4N202  or CO< NH•CH2 NH•CO the ureide of glycollic acid, may be obtained by heating allantoin or alloxan with hydriodic acid, or by heating bromacetyl urea with alcoholic ammonia . It crystallizes in needles, melting at 216° C . When hydrolysed with baryta water yields hydantoic (glycoluric) acid,H2N • CO .NH . CH2• CO2H, which is readily soluble in hot water, and on heating with hydriodic acid decomposes into ammonia, carbon dioxide and glycocoll, CH2•NH2•CO2•H . Many substituted hydantoins are known; the a-alkyl hydantoins are formed on fusion of aldehyde- or ketone-cyanhydrins with urea, the '3-alkyl hydantoins from the fusion of mono-alkyl glycocolls with urea, and the 7-alkyl hydantoins from the action of alkalis and alkyl iodides on the a-compounds. y-Methyl hydantoin has been obtained as a splitting product of caffeine (E . Fischer, Ann., 1882, 215, p . 253) .