Revision of the a2H value for N,N-dialkylhydroxylamines based on kinetic and spectroscopic measurements

Kinetic solvent effects on hydrogen-atom abstraction from N,N-diethylhydroxylamine and N,N-dibenzylhydroxylamine by the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH.) indicated that these compounds are much weaker hydrogen-bond donors than implied by the currently accepted a(2)(H) value of 0.453. Lower a(2)(H) values were also obtained by monitoring 1 : 1 complex formation with two strong hydrogen-bond acceptors, HMPA and DMSO, in tetrachloromethane using IR spectroscopy. It is concluded that the a(2)(H) value for sterically non-hindered N,N-dialkylhydroxylamines should be revised downward to 0.29.