Transition structures for conjugate and carbonyl additions of cyanide to s-cis- and s-trans-acrolein. An ab initio MO study

Abstract

Transition structures for the addition of cyanide anion to s-cis- and s-trans-acrolein and to ethylene and formaldehyde have been located with ab initio MO calculations with use of the 3-21 G and 6-31+G* basis sets. Energies of all stationary points, including reactants, ion-dipole complexes, and products, were evaluated at the second-order Moller-Plesset correlation level with the 6-31+G* basis set. The relative reaction barriers for conjugate and carbonyl additions are discussed for gas-phase and solution-phase reactions. Calculations predict that, in the gas phase, the reaction barrier for conjugate addition to s-cis-acrolein is slightly higher than that for carbonyl addition, wheareas the reverse situation is found for addition to s-trans-acrolein. The conjugate addition products are also more stable than the carbonyl addition products. The reaction barrier for carbonyl addition is expected to become smaller than that for conjugate addition in solution, under which conditions the difference in the stabilities of the conjugate and carbonyl products should become relatively small