TETRAZINES, in organic chemistry, a group of compounds containing the ring system CNN C N N CNC CNN, or NNC, or NNN; only derivatives of the first two types are known. The members of the first series may be prepared by oxidizing osazones (i.e. dihydrazones of a-diketones), dihydrotetrazines resulting. Dihydro-derivatives of the second type are formed from hydrazine and imino-ethers (A. Pinner, Ber., 1893, 26, p. 2126; 1894, 2 7, p. 984); these easily oxidize to the corresponding tetrazines, which are stable towards acids; their dihydro-derivatives, however, are decomposed, the group - NH-NH--being eliminated as hydrazine and replaced by oxygen, with consequent formation of the five membered oxybiazole ring. Concentrated acids convert the dihydro-tetrazines into isodihydrotetrazines, thus: - RCNHNH RCNHN RN :C R NNHCR, the N-alkyl derivatives of which type may be prepared by the action of alcoholic potash and chloroform on aromatic hydrazines.
Much discussion has circulated about the diazo-acetic ester, from which A. Hantzsch and 1900, 33, p. 58) obtained what they considered tetrazine, thus: CHCO 2 R H02CCHN:N N :N CHC02H N :N C. Billow (Ber., 1906, 39, pp. 2618, 4106), however, showed this substance to be an N-aminotriazole, which necessitates the first decomposition product being an acid (I.), the conversion into the (I.) HO 2 CCNH-NH H02CC - NNH2 triazole derivative (II.) being due to the ring opening on the addition of the elements of water and then closing again to the five-membered ring with elimination of water again. The decompositions of diazoacetic ester were then again examined by T. Curtius and his students (Ber., 1907, 40, pp. 262, 35 o, 45 0, &c.), who showed that both triazole and tetrazine derivatives could be obtained from the bisdiazo-acetic acid which is formed by the action of alkali on diazo-acetic ester.
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