New radical constants based on the sigma dot (sigma(x)) scale have been calculated for six new para substituents; N(CH3)(2), CHO, NH2, NO2, COOH and OH, of toluene using density functional based electronic structure methods. Calculated radical constants show excellent agreement with available experimental values. The study also clearly demonstrates that the calculated bond dissociation enthalpy (BDE) of para substituted toluenes depends solely on radical stabilisation. (c) 2006 Elsevier B.V. All rights reserved.