The Number of Normal Components of Essentially Disconnected Coronoid Systems

An essentially disconnected coronoid system is defined as a coronoid system with some Kekule structures and fixed bonds. The number of Kekule structures (or perfect matchings) of a coronoid system G is the product of the number of perfect matchings of each normal component in G. In this article, it is proved that the boundary polygon of a normal component without any vertex lying on the boundary of an essentially disconnected coronoid system is a hexagon. Consequently, a lower bound on the number of normal components of an essentially disconnected coronoid system is obtained.