ANALYSIS OF THE CHANGES ON THE POTENTIAL-ENERGY SURFACE OF MENSHUTKINREACTIONS INDUCED BY EXTERNAL PERTURBATIONS

A quantitative analysis of the changes induced by solvation and static uniform electric fields on the potential energy surface of the S(N)2 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 pert urbations yield transition states which are both electronically and st ructurally advanced as compared to the transition state in the gas pha se. The overall study is complemented with HOMO-LUMO orbital considera tions, 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.