Perturbed equilibria and statistical energy redistribution in a gas- phase S(N)2 reaction

The relative translational energy of one set of reactants in the gas- phase equilibrium between chloride ion and chloroacetonitrile 35Cl- + 37ClCH2CN ⇆ 37Cl- + 35ClCH2CN is varied without affecting the energy distribution of the other set. The steady-state ratio of ionic isotopes changes so that there is an increase in the concentration of energized reactants. The ratio provides a measure of the translational energy dependence of the rate constant for the bimolecular nucleophilic substitution (S(N)2) reaction. The observed energy dependence is indistinguishable from that predicted by Rice-Ramsperger-Kassel-Marcus theory, suggesting that the increased translational energy redistributes statistically in the collision complex.

Duke Scholars

Author Stephen L Craig Chemistry