ENUMERATION AND CLASSIFICATION OF CORONOID HYDROCARBONS

A coronoid is defined as a planar system of identical regular hexagons (no overlapping) with one or more holes of a size not less than two hexagons. The numbers of coronoids with h (number of hexagons) equals 8, 9, 10, 11, and 12 were found to be 1, 5, 43, 283, and 1954, respectively. A detailed report is given on a classification of the coronoids up to h equals 11. They are Kekulean or non-Kekulean. The former class is divided into catacondensed (normal), normal pericondensed, and essential disconnected (pericondensed). The non-Kekuleans (always pericondensed) are divided into obvious and concealed categories. It is pointed out that all integer values of DELTA are possible.