Abstract
Recently, we presented structure鈥搑eactivity correlations for the gas-phase rate constants for hydrogen abstraction from sp3-hybridized carbon by three electrophilic radicals (X鈥� + HCR3 鈫� XH + 鈥R3; X = Cl鈥�, HO鈥�, and Br鈥�); the reaction enthalpy effect was represented by the independent variable 螖rH and the 鈥減olar effect鈥� by the independent variables F and R, the Hammett鈥揟aft constants for field/inductive and resonance effects. Here we present a parallel treatment for the less electronegative CH3鈥�. In spite of a limited and scattered database, the resulting least-squares fit [log鈥痥437(CH3鈥�) = 鈭�0.0251(螖rH) + 0.96(危F) 鈥� 0.56(危R) 鈥� 19.15] was modestly successful and useful for initial predictions. As expected, the polar effect appears to be minor and its directionality, i.e., the 鈥減hilicity鈥� of CH3鈥�, may depend on the nature of the substituents.