A quantitative analysis of the changes induced by solvation and static uniform electric fields on the potential energy surface of the SN2 Menshutkin-type reaction between ammonia and methyl chloride has been performed with the help of different indexes. These indexes have been defined to account for the structural and electronic degree of advance of the transition state with respect to the reactant complex and ion pair product through the use of geometrical parameters, dipole moments and electron density distributions. Indexes reveal that external perturbations yield transition states which are both electronically and structurally advanced as compared to the transition state in the gas phase. The overall study is complemented with HOMO-LUMO orbital considerations, quantification of the global charge density redistributions by means of quantum molecular self-similarity measures and an analysis of the topological features of electron density distributions.
The Institute of Computational Chemistry of the University of Girona dedicated this contribution to Professor Joan Bertran i Rusca on the occasion of his 65th birthday.