: Comparisons of fluorene, phenalene, and benzanthrene sp3C-H homolytic bond dissociation energy data, data collected with the aid of a cycle that utilizes acid-base and redox data collected in dimethyl sulfoxide solution, indicate that the sp3C-H bonds in phenalene and benzanthrene are about 18 and 16 kcal/mol weaker (in a homolytic sense) than the sp3C-H bond in fluorene. © 1990, American Chemical Society. All rights reserved.