The reactions of 4-nitrophenylhydrazine and phenylhydrazine with formaldehyde

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).