On Construction of k-Clar Structures

Already in the case of smaller benzenoids, such as benzo[ghi]-perylene, it may be somewhat tedious to find by inspection of all the 

Kekule valence structures all the combination of Kekule valence structures of interest. The same is also true for finding combinations of Kekule valence structures involved in HH-Clar structures. A better way to obtain the correct combinations of Kekule valence structures instead of construction of various superpositions is to first write down k-Clar structures (or HH-Clar structures) and then decompose them into underlying Kekule valence structures. The apparent difficulty that remains in such an approach, that cannot be avoided, is the case of benzenoids having a large number of Kekuld valence structures which results in large number of decomposition. 

Let us clarify what we mean as the derivative structure by returning to Fig. 15 in which we listed the six k-Clar structure of 

The above illustration suggests an algorithm for construction of k-Clar structures that can be outfined as follows  

This algorithm as stated can be readily implemented in a computer program, even though it may be somewhat demanding when applied to systems having a larger number of Kekule structures. 

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