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 |
| |
Authors: | V. J. Klimkowski,Lothar Sch fer,Robert K. Bohn |
| |
Affiliation: | V. J. Klimkowski,Lothar Schäfer,Robert K. Bohn |
| |
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. |
| |
Keywords: | |
|
|