To study the size-dependent properties of the n-perfluoroalkyl associations, the highpressure-limit rate coefficients for the four reactions considered have been plotted together in At all temperatures, the self-association reaction of C 2 F 5 possesses the lowest rate coefficient. Both steric and electronic effects can contribute to this behavior. Bulky trifluoromethyl groups attached to not one, but both fragments involved, generate comparatively unfavorable steric effects along the reaction coordinate, and the potential along the MEP is also seen to be less attractive than for all the other cases. At higher temperatures, the self-association reaction of CF 3 possesses a consistently higher rate coefficient than both of the cross-association reactions. Given that the optimal transition-state dividing surfaces at these temperatures are located at shorter separation distances, the observed trend can be explained by steric effects. At lower temperatures, the optimal transition-state dividing surfaces are located at further separations. Thus, the higher coefficients for the cross-association reactions can likely be justified by their more attractive potentials along their MEPs. As temperatures rise into more intermediate levels, a combination of the steric and electronic effects described above appear to determine the size-dependent behavior of the association rate constants.