Kinetics analysis of the idealized heavy hydrocarbon system comprising a reactant A(1) = mu H-1 converting through a Rice-Herzfeld chain in the presence of a chain transfer solvent A(2) = mu H-2 revealed the conditions and structural features of A(2) for optimal rate enhancement E-1 = r(A1) (A(1), A(2))/r(A1)(A(1)) = (1 + (k) over capS theta)/(1 + (k) over capS), where (k) over cap= k(12)/k(21) is the index of chain transfer and theta = k(21)/k(11) is the index of the kinetic effect of chain transfer. Imposition of the Evans Polanyi relationship for these two hydrogenabstraction reactions rendered El as a function of the mu(2)-H bond strength x = d(mu 2H)(o) for a given reactant A(1). Qualitatively, (K) over cap decreases and 0 increases with increasing values of x. For low values of S, the intuitive optimum is where the balance between these two dependencies is found. For higher values of S, the optimal value of x is defined by the condition d theta/(theta-1) = d (K) over cap S/((K) over capS(1+(K) over cap S)).