Knowledge Bank

“By considering the catacondensed hydrocarbons, $C4v+2H2v+4$ (e.g. naphthalene, anthracene, phenanthrene, benzanthracene, etc.), as distorted cyclic polyenes with `cross-link’ perturbations, it becomes a relatively simple matter to calculate by group theory and perturbation theory how substituent-induced changes in the $\pi$-electronic spectra of catacondensed hydrocarbons should depend on the number and relative positions of the substituent groups. Within the approximation of first and second order perturbation theory, the formulas for the frequency shifts and intensity changes derived on this basis are particularly simple, being analogous to the well known Sklar-Forster rules for substituted benzenes. In this talk, the method of deriving the appropriate formulas for any transition between two $\pi$-electronic states will be discussed briefly. The remaining time will be spent in discussing the application of theoretical results to the correlation and interpretation of various sets of spectroscopic data on substituted catacondensed hydrocarbons available in the literature to date.”