conservation of orbital symmetry
The @O04320@ control of concerted reactions; this requires @T06446@ of the molecular orbitals of reactants into those of products to proceed continuously by following a @R05174@ along which the symmetry of these orbitals remains unchanged. Reactions which adhere to this requirement are classified as symmetry-allowed reactions, and those which do not as symmetry-forbidden reactions.
PAC, 1999, 71, 1919. (Glossary of terms used in theoretical organic chemistry) on page 1931 [Terms] [Paper]