Solvent Effects on Acrylate kp in Organic Media: A Response

Radical propagation rate is adequately understood in the light of fundamental kinetic theory. Differences in bulk and solution k(p) are primarily of entropic origin, with the effects depending on the differences in polarity and size of monomer and solvent molecules, respectively. Experimental data for the propagation rate coefficient of secondary acrylate radicals demonstrate that bulk and solution-in-toluene k(p) exhibit distinctly different behavior. Bulk k(p) is clearly enhanced in passing from methyl acrylate (MA) to dodecyl acrylate (DA), whereas solution-in-toluene k(p) is approximately constant with a slight tendency to decrease from MA to DA. This kp behavior has also been found in a recent study, in which it has, however, been concluded that k(p) in solution of toluene (and of butyl acetate) displays a similar behavior to bulk. This surprising and ina-dequate conclusion requires the present comment and rectification to be made.