conservation of orbital symmetry
The @[email protected] control of concerted reactions; this requires @[email protected] of the molecular orbitals of reactants into those of products to proceed continuously by following a @[email protected] 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]