Symmetry Forbidden Definition:
A reaction that disobeys conservation of orbital symmetry.
Symmetry Forbidden Explained:
Fontier orbitals, we find that the phases of the MOs do not overlap. This reaction is therefore said to be symmetry forbidden, and the reaction does not occur. A [2+2] cycloaddition. Can only be performed with photo chemical excitation. When one of the compounds is subjected to UV light, it can absorb the light to promote a p electron to the next higher energy level. In this excited state.