Algorithm and Annulenoid Kekule Structures for Primitive Coronoids

2 Algorithm and Annulenoid Kekule Structures for Primitive Coronoids 

The algorithm is illustrated below the same example as in Gutman and Cyvin (1989) is used, but a different angularly annelated hexagon (of mode A2) has been chosen as A. 

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. 

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

The improper annulenoid Kekul6 structures possess aromatic sextets in contrast to the proper ones, and they are included in the sets of k and k Kekul6 structures, one in each set. 

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