Relative reactivities of radicals derived from several 1-(N,N-dimethylamino)ethylene-2-derivatives towards the polymerization of butyl acrylate have been calculated. It has been observed that the reactivity of the radicals increases as the electron withdrawing character of the groups attached in the beta position to the N atom increases. The experimental efficiency factor (f) has been found to be proportional to the sigma(F) value defined in the Taft equation. The dependence of the reactivities with the nature of the radicals has also been explained through their frontier orbital characteristics. The presence of heteroatoms next to the radical center could modify, in some cases, the accuracy of these calculations, although the inclusion of more sophisticated quantum-mechanical methods does solve this drawback. Moreover, the enthalpy calculation of the possible radicals formed from a certain molecule gives a good approach to realize about the existence of anomalous behaviors.