Tetrazoles

Tetrazoles, in organic chemistry, a group of heterocyclic compounds, capable of existing in two isomeric series (formulae I 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 J. A. Bladin by elimination of the phenyl group (by nitration, reduction, &c.) and of carbon dioxide obtained free tetrazole, CH 4 N 2; 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. I); from the action of nitrous acid on phenylthiosemicarbazide; and by the action of arylazoimides on aldehyde hydrazones (0. Dimroth, Ber., 1907, 40, p. 2402). The tetrazoles behave as strong monobasic acids, and are exceedingly stable. A series of tetrazolium bases (formula 3) have been obtained by H. V. Pechmann (Ber., 18 94, 2 7, p. 2920) starting from formazyl compounds (formula 4), which are oxidized by means of amyl nitrite and hydrochloric 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 <NNH /N :CH RHN - N: CH HN N:CH or N N:CH RN / RN :N HO R (1), (2), (3), (a).