In this paper, the impact of conformational effect (including stereoelectronic effect and steric effect) on the stereoselectivity in some organic reactions were discussed by estimating the energy difference between the intermediates of the competing reaction routes. Stereoelectronic effect and steric effect played a more or less important roles respectively in affecting the stereochemistry of the reactions because of different reaction mechanisms, conformational structures of the reactants and the reaction conditions. Revealing such relationship would be helpful in correctly predicting the structure of the products and selecting a more practicable synthetic route.

Key words: TRANSITION STATE THEORY, ORGANIC SYNTHESIS, CYCLOHEXANE P, SPIRO COMPOUNDS