The reactions of 4-nitrophenylhydrazine and phenylhydrazine with formaldehyde

Abstract

A comparison has been made of the reaction products from 4-nitrophenyl- hydrazine and formaldehyde with those obtained from phenylhydrazine and formaldehyde. Formaldehyde 4-nitrophenylhydrazone does not form a stable dimer analogous to 1,4-diphenylhexahydro-s-tetrazine (1) formed from formaldehyde phenylhydrazone. On heating formaldehyde 4- nitrophenylhydrazone to 180°, or on heating a solution of the monomer in glacial acetic acid, oxidative coupling takes place to give glyoxal bis(4-nitrophenylhydrazone). Three products from 4-nitro- phenylhydrazine and excess formaldehyde have been shown to be (6), (7), and (8), with the unsymmetrical C₁₆H₁₆N₆O₅ isomer (8) predominant. An explanation has been provided for the formation of the symmetrical and unsymmetrical C₁₆H₁₆N₆O₅ isomers (7) and (a), both having a -CH₂OCH₂- grouping, and of only one -CH₂- bridged product. Alternative structures are suggested for an ethoxy compound, (11) or (12), formed from 4- nitrophenylhydrazine and formaldehyde in ethanolic solution. The N.M.R. spectra of a number of reaction products have been examined, and an unusual long-range coupling has been observed between the C 3 and C 5 methylene group protons in 4-anilino1-2-phenyl-2,3,4,5-tetrahydro- 1,2,4-triazine (4).