Changes in the Electronic Transitions of Aromatic Hydrocarbons on Chemical Substitution. I. Perturbation Theory for Substituted Cyclic Polyenes

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Abstract
General formulas are derived by first‐ and second‐order perturbation theory for the changes in the transition moment, transition probability, and frequency of aromatic cyclic‐polyene transitions produced by ideal chemical substitutions. The changes are described in terms of the interactions of three kinds of prototype electronic states: carbon‐ring states, substituent states, and charge‐transfer states. The interaction of the ring states with one another is regarded as an inductive effect of substitution; the interaction with the substituent and charge‐transfer states, as a conjugative effect. Using the symmetry properties of the prototype states and assuming that the interactions are caused by a sum of perturbation operators for the individual of substituents, it is shown how the changes depend on the nature, the number, and the positions of the substituents on the ring. Formulas pertaining to the singlet‐singlet pi‐electronic transitions in benzene are given.