Adiabatic Connection Method for X^- + RX Nucleophilic Substitution Reactions (X = F, Cl)

Kormos, B.; Cramer, C. J.
J. Phys. Org. Chem. 2002, 15, 712.

A modified Perdew-Wang one-parameter hybrid density functional (mPW1N) has been developed for nucleophilic substitution reactions by optimizing the fraction of exact exchange in vPW1PW91/6-31+G(d). Activation energies for twenty identity nucleophilic substitution and alkyl halide heterolysis reactions involving fluorine and chlorine were compared to values computed at the MCG3//MC-QCISD level to arrive at an optimal value of 40.6% HF exchange in mPW1N. This choice also leads to improved transition state geometries over the training set. Results from mPW1N are compared to those from other common DFT methods, and some sources of error are explored.

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