Ab initio through space/bond interaction analysis on the stereoelectronic effect by modifying the exponents of the basis set

The concept of the stereoelectronic effect has been widely used for the elu cidation of organic reaction mechanisms. However, a detailed analysis of th is effect has not been developed, especially at the level of the ab initio molecular orbital method. In the present article, the through space/bond in teraction analysis was applied to the stereoelectronic effect at the level of the ab initio molecular orbital method. To obtain a reliable result for the through space/bond interaction analysis, we introduced a novel procedur e to cut off a specific through space/bond interaction, that is, cutting of f a specific integral is performed by increasing the absolute magnitude of the exponent in a Gaussian function. By this procedure, we can easily find a balance in cutting off the nuclear-electron attractions, the nuclear-nucl ear repulsions, and the electron-electron repulsions. By using the above-me ntioned procedure, we carried out a through space/bond interaction analysis to the stereoelectronic effect for aminomethanol as a model molecule. As a result, the diagonal terms for the electron transfer play a more important role than do the off-diagonal terms. Since the diagonal term corresponds t o the conventional steroelectronic effect, the obtained result is in accord ance with the conventional model for the stereoelectronic effect. This resu lt may give a novel insight into the stereoelectronic effect. (C) 1999 John Wiley & Sons, Inc.