Gas-Phase Chemistry of the Negative Ions Derived from Azo- and Hydrazobenzene

Article abstract of DOI:10.1021/jo00002a023

The proton affinities of the azobenzene radical anion and the conjugate base of hydrazobenzene have been determined to be 1465 kJ mol^-1 and 1514 kJ mol^-1, respectively, with the use of a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer equipped with an external ion source.The proton affinities lead in combination with a measured electron affinity of azobenzene (55 kJ mol^-1) to a N-H bond dissociation energy (BDE) of 306 kJ mol^-1 for hydrazobenzene while the N-H BDE of the PhNHN^.Ph radical is estimated to be 208 kJ mol^-1.The difference between the N-H BDE values of 98 kJ mol^-1 approximates the ?-bond energy of the nitrogen-nitrogen bond in azobenzene.The reaction of the PhN^.N^-Ph and PhNHN^-Ph ions with derivatives of trifluoroacetic acid are characterized.The occurrence of dissociative electron transfer instead of S_N2 substitution in reactions of the azobenzene radical anion with halogen-substituted methanes is discussed.