Kinetic study of 1,5-hydrogen transfer reactions of methyl acrylate and butyl acrylate using quantum chemistry

1,5-Hydrogen transfer reactions in methyl acrylate and butyl acrylate free-radical polymerization are studied using quantum chemistry and transition state theory to estimate the kinetic parameters (k _tr, E _a, and A) with tetrameric radicals, requiring a number of atoms that ranks among the largest polymeric mimics to date. A two-step transformation accounted for the overall reaction: rotation from an extended conformation to a coiled conformation and abstraction of the fifth hydrogen atom by the end-chain radical. UB3LYP/6-31G(d) was used for geometry optimization, validation of the transition states, and calculation of frequencies that were used to obtain thermodynamic properties. The more computationally demanding level of theory, MPWB1K/6-31G(d,p), was used for calculation of the electronic energy.