Proton transfer reactions between 4-nitrophenylphenylcyanomethanes and cyclic nitrogen bases in acetonitrile solvent

3,3,6,9,9-Pentamethyl-2,10-diazabicyclo[4.4.0]dec-1-ene has been synthesized and its proton transfer reactions, together with those of the bases 2,2,6,6-tetramethylpiperidine and 1,2,2,6,6-pentamethylpiperidine, have been studied with the carbon acids 4-nitrophenylphenylcyanomethane and 2-methyl-4-nitrophenylphenylcyanomethane. Equilibrium constants, rate constants, primary deuterium isotope effects, and activation parameters are reported for the reactions in acetonitrile solvent. Values of the pKa in acetonitrile have been measured for the conjugate acid of each base and the Brønsted β value of 0.56 in acetonitrile has been determined for the proton transfer from 4-nitrophenylphenylcyanomethane.