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Ab initio studies of structural features not easily amenable to experiment. 32. Conformational analysis and molecular structures of isopropyl and ethyl formate and comparison with spectroscopic data

✍ Scribed by V. J. Klimkowski; Lothar Schäfer; Robert K. Bohn

Publisher
John Wiley and Sons
Year
1984
Tongue
English
Weight
509 KB
Volume
5
Category
Article
ISSN
0192-8651

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✦ Synopsis

Abstract

The geometries of several conformations of ethyl and isopropyl formate were optimized by the ab initio gradient method on the 4‐21G level. The calculations are in agreemnt with the existence of two conformers of ethyl formate of nearly equal energy. The COCC torsional angle in one is anti (180°) and in the other is gauche (about 80°). The equilibrium configuration of the isopropyl group in the formate is found to be unsymmetrical, with a COCH torsional angle of about 40°. A second minimum of torsional energy, at COCH = 180°, is 1.2 kcal/mol less stable than the unsymmetrical form. The calculations demonstrate the tranferability of internal rotational‐potential parameters and of conformationally dependent geometrical trends between ethyl and isopropyl formate. There is good agreement between the calculated results and empirical potential‐energy functions and rotational constants determined from microwave spectroscopy.

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