THE WEAKLY STRAINED BENZENE CHROMOPHORE AND THE INTERACTION VECTOR MODEL OF THE SECONDARY TRANSITION, IN TETRALINE LIKE MOLECULES, IN TOCOPHEROLS, THYMOL, TETRAHYDROCANNABINOL, AND CANADINE

Many natural products display a benzene chromophore with simple pi don ating substituents such as alkyl, -OR, or -NH2 groups. Often these mol ecules bear rings fused to the benzene moiety,and the strain imposed b y these rings induces specific behaviours. (1,2) The intensity of the secondary transition (towards 255 nm for the benzene molecule itself) has been a puzzling challenge during many years for the experimentalis t, unless he could use sophisticated quantum approaches, unfitted to i ts needs. The SKLAR's vector approach has been quite interesting, but far too much qualitative. (3) It has been shown recently,using simple vector addition rules within the interaction vector model(4,5) (IVM), that it is possible to calculate the intensity of the secondary transi tion of the benzene chromophore in the above molecules, on a simple ba sis. The present work will be devoted to show how to extend the applic ation of the IVM to other molecules displaying six membered fused ring s with weak strain effects, and doing so to test the limits of the mod el. Experimental intensity is given as epsilon(sm), the maximum of the smoothed absorption curve, as it has been defined by BALLESTER and RI ERA (6) (the calculated value is :epsilon(sm,c)). The epsilon(sm) valu es given in their work are used when necessary.