Nitriles with exceptionally high proton affinity due to a C–N bond formation upon protonation

Abstract

In this work, we show that nitriles whose CN group is in the vicinity of an electron pair-donating group exhibit exceptional higher proton affinity than the ordinary nitriles in the gas phase and solution. The exceptional proton affinity of these compounds is partly due to the formation of a new bond between the C atom of CN and the atom with the electron pair upon protonation of the N atom of the CN group. The calculated proton affinities and gas phase basicities confirm that these compounds have comparable or even higher basicities than simple organic superbases such as proton sponges, guanidine, and phosphazene derivatives. The calculations in acetonitrile showed that some of these nitriles also exhibit high basicity in solution with pKa(BH+) ≥ 25.