Synthesis of aliphatic hydrazonyl bromides and kinetics of their conversion into hydrazides

Abstract

The hydrolytic conversion of N-(4-nitrophenyl)-, N-(2-bromo-4-nitrophenyl)-, and N-(2,4-dinitrophenyl)-alkanohydrazonyl bromides into the corresponding alkyl hydrazides has been investigated kinetically in 80% aqueous dioxan. The rates of hydrolysis for all three series of compounds were found to decrease with increasing alkyl substitution. This was attributed to the bulk of the alkyl group retarding solvolysis, since electron-withdrawing groups strongly retard reaction. Further evidence (large solvent, common-ion, and salt effects) also supports a mechanism involving rate-determining unimolecular ionization. The reaction of benzenediazonium ion with the parent hydrazones was also investigated and showed the same dependence on the bulk of the aliphatic group.