2. We must be cautious in applications to species other than hydrocarbons. The current BEBOP model overestimates the strength of each --C -F bond by ∼ 10 kcal/mol, and often underestimates the strength of C --O bonds by a comparable error. These effects combine to produce a BEBOP error of more than 30 kcal/mol for the C -F bond dissociation energy of F 2 C --O.