A concealed property of total pi-electron energy

In the theory of total Tc-electron energy (E) an auxiliary quantity is defi ned via gamma* = [n(2mn - E-2)]/ [2m(2m + n - 2E)], where n and m denote th e number of vertices and edges of the molecular graph. Within classes of st ructurally similar conjugated systems a very good linear correlation betwee n gamma* and n is observed, apparently contradicting to the way in which ga mma* (by definition) depends on n, m, E. We now establish the condition whi ch E must satisfy, in order that gamma* be a linear function of n: the cond ition for an exact linear relation between - and n is E = m. (C) 2001 Publi shed by Elsevier Science B.V.