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A Comparison of the Rotational Potential Functions in Butane, Propylsilane, Ethylmethylsilane, and 1,2‐Disilylethane: Ab Initio and MM2 Results
Author(s) -
Profeta Salvatore,
Unwalla Rayomand J.,
Nguyen Binh T.,
Cartledge Frank K.
Publication year - 1986
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/jcc.540070416
Subject(s) - ab initio , basis set , conformational isomerism , chemistry , van der waals force , ab initio quantum chemistry methods , computational chemistry , potential energy , bond length , steric effects , molecular geometry , yield (engineering) , molecular physics , atomic physics , crystallography , thermodynamics , physics , density functional theory , molecule , stereochemistry , organic chemistry , crystal structure
Ab initio calculations at several basis set levels were used to examine the rotational potential energy function around the CC bond of 1,2‐disilylethane, also known as disilabutane (DSB). The best basis set for this system was found to be the 3‐21G(*) basis, which was also used to verify the potential function around the CH 2 —SiH 2 segment in ethylmethylsilane (EMS). The torsional parameters developed by Frierson and Allinger for the CSiCC fragments were shown to yield a potential in excellent agreement with those from the 3‐21G(*) basis. Full 3‐21G(*) geometry optimizations were performed on the 0°, gauche (60°), and 180° conformers of DSB and EMS. Data derived from the ab initio calculations on DSB were used to establish MM2 torsional and bond length parameters for the SiCCSi fragment. The MM2 and ab initio structures agree well. A detailed comparison of rotational potentials and the steric energy components is presented. We also report the torsional potential of propylsilane (PS) and compare the MM2 calculated structure with experiment. Our findings suggest that the similarity of the torsional potentials of butane and DSB and the dissimilarity between butane and EMS arise from the same phenomenon—van der Waals interactions that are attractive rather than repulsive dominant.