Methyl and Hydrogen Transfer in Free Radical Reactions

It was speculated that hydrogen transfer was not the only type of transfer reaction that could take place during thermal conversion, and that methyl transfer could also take place. There was a large body of literature on intramolecular methyl migration, but little mention of intermolecular methyl transfer as a potentially important reaction type in free radical systems. Methyl transfer during thermal conversion at 400 °C was investigated using indene, 2-methylindene and α-methylstyrene. It was demonstrated that methyl transfer took place. Reaction products that could be explained only in terms of intermolecular methyl transfer were identified, including products that were formed by transfer of two methyl groups. Thermal conversion that considered both intermolecular methyl transfer and hydrogen transfer highlighted potential implications for industrial practice. Products from methyl transfer were more reactive for thermally induced free radical initiation and hydrogen/methyl transfer reactions. Methyl transfer during molecule-induced homolysis provided a plausible pathway for release of methane that does not require a reaction involving hydrogen and methyl radicals. This work not only showed the importance of intermolecular methyl transfer in free radical systems, but also indicated that methyl transfer as opposed to hydrogen transfer affected the composition and bulk properties of the reaction product.