TETRAZOLES, in organic chemistry, a group of hetero cyclic compounds, ” capable of existing in two isomeric series (formulae 1 and 2), although the methods of preparation do not always permit discrimination between the possible isomers. They are prepared by the action of nitrous acid on cyanamidrazone (dicyanophenylhydrazine) and hydrolysis of the resulting nitrile, from which I. A. Bladin by elimination of 'the phenyl group (by nitration, reduction, &c.) and of carbon dioxide obtained free tetrazole, CH4N2; from amidines by the action of nitrous acid, followed' by the reduction of the intermediately formed dioxytetrazotic acids with sodium amalgam; from amidoguanidine by diazotization, the diazonium nitrate-» on treatment with acetates or carbonates yielding aminotetrazole (J. Thiele, Ann., 1892, 270, p. 1); from the action of nitrous acid on phenylthiosemicarbazide; and by the action of arylazoimides on aldehyde hydra zones (O. Dimroth, Ber., 1907, 40, p. 2402). The tetrazoles behave as strong mono basic acids, and are exceedingly stable. A series of tetrazolium bases (formula 3) have been obtained by H. V. Pechmann (Ber., 1894, 27, p. 2920) starting from formazyl compounds (formula 4), which are oxidized by means of amyl nitrite andihydrochloric acid. They are strong bases, which in aqueous solution, absorb carbon dioxide readily. The free bases have not been isolated, but their salts are well-crystallized solids.
N=N /N-NH N:CH RHN~N:CH
HN N:CH°rNN:CH RN NN RN:N
HO R
(1), (2). . (3), (4)