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 elucidation of organic reaction mechanisms. However, a detailed analysis of this effect has not been developed, especially at the level of the ab initio molecular orbital method. In the present article, the through space/bond interaction 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 procedure to cut off a specific through space/bond interaction, that is, cutting off 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-nuclear repulsions, and the electron-electron repulsions. By using the above-mentioned 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 to the conventional steroelectronic effect, the obtained result is in accordance with the conventional model for the stereoelectronic effect. This result may give a novel insight into the stereoelectronic effect.