Dipole Moment as a Possible Diagnostic Descriptor of the Conformational Isomerism of the Ammonia Molecule

Abstract

In this chapter, Ghosh and Rajak have made a detailed quantum mechanical study of the variation of the dipole moment of ammonia as a function of its conformations evolving during the process of its umbrella inversion by invoking their method of dipole correlation of electronic structure as basis. Ghosh et al discover a surprising result that the variation of dipole moment mimics the total energy curve as a function of reaction coordinates revealing the fact that the dipole moment is one possible diagnostic descriptor of the conformational isomerism of molecules containing lone pair electrons. The dipole is calculated and partitioned into bond and lone pair components for a large number of conformations between the equilibrium shape and the transition state of inversion and the results are interpreted and correlated in terms of the localized molecular orbitals, LMOs generated from the canonical molecular orbitals, CMO’s of each conformation. Anderson, from the concept of space time symmetry, postulated that ammonia has zero dipole moment. Present study reveals that Anderson’s correlation relied upon the bond moment only while the major component of dipole of ammonia originates from the lone pair of nitrogen.