Some structural relationships between acenes and cyclacenes both Hucke
l- and Mobius-type and within the same class of compounds were demonst
rated by the recursive analysis of their E-pi and I-pi values or the f
irst differences thereof. It was found that the first differences of E
-pi and I-pi tend to have certain limit values as the number of benzen
oid rings increases in each class of compounds studied.