Equilibrium Acidities and Homolytic Bond Dissociation Energies of N−H and/or O−H Bonds in N-Phenylhydroxylamine and Its Derivatives

The equilibrium acidities (pKHA values) in DMSO of the following hydroxylamines have been measured: (1) N-phenylhydroxylamine and its p-bromo and p-cyano derivatives, (2) N-benzyl-N-phenylhydroxylamine and its p-bromo and p-cyano derivatives, (3) O-benzyl-N-phenylhydroxylamine, (4) N-benzoylphenylhydroxylamine and its p-bromo and p-cyano derivatives, and (5) N-hydroxylpiperidine. The BDEs of the O−H and/or N−H bonds in these 11 weak acids have been estimated by combining their pKHA values with the oxidation potentials of their conjugate bases according to the following equation: BDEHA = 1.37pKHA + 23.1Eox(A-) + 73.3 kcal/mol.