Iterative estimation of total π-electron energy

In this work, the lower and upper bounds for total π-electron energy (E) was studied. A method is presented, by means of which, starting with a lower bound E L and an upper bound E U for E, a sequence of auxiliary quantities E 0 , E 1 , E 2 ,... is computed, such that E 0 = E L , E 0 < E 1 < E 2 <..., and E ∞ = E U . Therefore, an integer k exists, such that E k ≤ E < E k + 1 . If the estimates E L and E U are of the McClelland type, then k is called the McClelland number. For almost all benzenoid hydrocarbons, k= 3.