The Equilibrium and the Determination of D₀⁰ (H—CN)

Abstract

The rate constants and equilibrium constant for the proton transfer reaction [Formula: see text] have been measured at 296 ± 2 K using the flowing afterglow technique: k forward = (2.9 ± 0.6) × 10 −9 cm 3 molecule −1 s −1 , k reverse = (1.8 ± 0.4) × 10 −10 cm 3 molecule1 s −1 , and K = 16 ± 2. The measured value of K corresponds to a standard free energy change, ΔG 296 °, of −1.6 ± 0.1 kcal mol −1 which provides values for the standard enthalpy change, ΔH 298 °= −1.0 ± 0.2 kcal mol −1 , the bond dissociation energy, D 0 0 (H—CN) = 124 ± 2 kcal mol −1 , and the proton affinity, p.a.(CN − ) = 350 ± 1 kcal mol −1 .