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Internet Electronic Journal of Molecular Design - IEJMD, ISSN 1538-6414, CODEN IEJMAT
| ABSTRACT - Internet Electron. J. Mol. Des. January 2005, Volume 4, Number 1, 31-58 |
A Density Functional and Molecular Orbital Study of the Methylamine Conformers
Dulal C. Ghosh
Internet Electron. J. Mol. Des. 2005, 4, 31-58
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Abstract:
The physical process of the conformational isomerism of
methylamine, H3C-NH2, molecule is studied by density
functional theory, DFT and CNDO SCF MO theory. It is
demonstrated that a number of molecular orbital and density
functional parameters are quite efficient in depicting the
rotation-induced fluctuation of molecular structure. The hardness profile
demonstrates that the evolution of molecular conformations of
methylamine under internal rotation about C-N bond is in
accordance with the maximum hardness principle, MHP. An
energy-partitioning quest of the origin of barrier to internal
rotation is performed. A detailed study of the variation of the
decomposed energy components as a function of torsional
variables reveals that all the one- and two-center bonded and
nonbonded interactions exhibit conformational dependence and
have differential stabilizing effect on staggered and eclipsed
conformations. The study of the nature of the profiles of the one
and two center decomposed energy components as a function of
torsional angle demonstrates that a number of such energetic
effects follow the dynamics of internal rotation of the
methylamine molecule so closely that a number of such energy
components can be used as the descriptor potential functions of
the process of rotational isomerization reaction of the molecule.
The present study concludes unequivocally that barrier does not
originate from some intramolecular nonbonded repulsion rather
the process of the origin and development of barrier involves the
whole skeleton of the molecule.
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