On the spectacular structural isomorphism between CnHs monoradical and Cn+sHs+3 diradical benzenoid hydrocarbons: from reactive intermediates to vacancy (Hole) defects in graphite

The formula/structure informatics of monoradical and diradical benzenoid hydrocarbons that are potential reactive intermediates is studied. Some new enumeration and structural results with analytical expressions are presented. The topological paradigm and one-to-one correspondence between the monoradical and diradical constant-isomer series is demonstrated. Constant-isomer benzenoid monoradicals of the formula CnHs have a one-to-one correspondence in isomer number and topology to constant-isomer diradicals of the formula Cn+sHs+3. Some electronic properties of benzenoid radicals are delineated. Excising out a monoradical or diradical benzenoid carbon molecule from a perfect hexagonal graphite layer leaves a matching monoradical or diradical vacancy hole defect called an antimolecule; this observation can be generalized to include excising out all nondisjoint and obvious benzenoid polyradicals from a perfect (Kekuléan) hexagonal graphite layer. It is shown that the characteristics of graphite vacancies (antimolecules) can be deduced from knowledge about the carbon molecules removed in their formation.