Annulenoid Kekule structure

Algorithm and Annulenoid Kekule Structures for Primitive Coronoids... 

The origin to the number 2 under point (3) of the above algorithm are the two annulenoid Kekule structures, which have been referred to as proper annulenoid or in—phase (Cyvin SJ 1990). They are indicated below. 

Notice that the two perimeters of kekulene have merged into one. In consequence, Mobius—kekulene has only two annulenoid Kekule structures versus the number four in kekulene (cf. Par. 2.5.2). The total number of Kekule structures in Mobius—kekulene is K = 198 (Cyvin 1990). 

There exist also two improper annulenoid or out-of—phase Kekule structures of a primitive coronoid (Cyvin SJ 1990). In the present example ... 

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