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Molecular mechanics studies (MM4) of sulfides and mercaptans
Author(s) -
Allinger Norman L.,
Fan Yi
Publication year - 1997
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/(sici)1096-987x(19971130)18:15<1827::aid-jcc1>3.0.co;2-q
Subject(s) - ab initio , chemistry , conformational isomerism , torsion (gastropod) , force field (fiction) , standard enthalpy of formation , computational chemistry , ab initio quantum chemistry methods , thermodynamics , molecule , physics , organic chemistry , quantum mechanics , medicine , surgery
The MM4 force field has been extended to the title class of compounds. The vibrational spectra, structures, conformational equilibria, and heats of formation have been studied for 47 conformers of 29 compounds. In general, the properties may be calculated with accuracy that is competitive with that for hydrocarbons. The structures are better fit than previously because of the inclusion of a torsion–bend interaction term, which has its origin in the lone pair (Bohlmann) effect. Available experimental data do not suffice to yield detailed torsional potentials, or geometries as a function of torsion angle, and these quantities were determined by ab initio calculations at the MP2/6‐31G* level. The rms error in the calculated frequencies of seven representative structures (with a total of 64 experimental and 96 ab initio frequencies) is 25 cm −1 . The heats of formation for 23 compounds have a weighted rms error of 0.36 kcal/mol. © 1997 John Wiley & Sons, Inc. J Comput Chem 18 : 1827–1847, 1997