STUDY ON VARYING RULE OF THE ELECTRON POL ARIZABILITY OF STRAIGHT-CHAIN POLYENE WITH INCREASING OF CARBON-CHAIN LENGTH

In this paper, the quantum chemistry method introduced within external electric perturbation field approach is used to calculate the electro n polarizability of straight-chain polyene H-(CH=CH)(n)-H(n=1, 2, ... ..., 15). Further, we adopt the alpha(1), the electron polarizability of ethene, as the value of reference, using the relational expresion a lpha(n) = a(n) . alpha(1) . n to discuss the varying rule of electron polarizability of sigma, pi and total electron system with the increas ing of n. The results show: (1) the a(sigma)(n) approach a constant 1 very much, i.e. alpha(sigma)(n) = alpha(sigma)(1) . n; (2) the a(pi)(n ) increases obviously at first, then the increasing vilocity decreases gradually, when the n is over a certain value n(0) the alpha(pi)(n) t end to a limit, i.e. when n < n(0), alpha(pi)(n) = a(pi)(n) . alpha(pi )(1) . n and a(pi)(n) > a(pi)(n - 1), when n greater than or equal to n(0), alpha(pi)(n) = a(pi)(n(0)) . alpha(pi)(1) . n; total valence ele ctrons' is same as pi electrons'. Otherwise, we use the picture of dis placement of gravity-center of electron distribution to describe this conclusion.