Alkylation of the toluene methyl group: A DFT study

Alkylation of the methyl group of toluene was modeled at the B3LYP/6-311++G∗∗ level. In the presence of Na2; the model basic catalyst, the methyl group is more active for the Na/H exchange than the H atoms at the aromatic ring. The PhCH2Na molecule formed is next alkylated by ethene to produce PhC3H6Na. This needs a 30 kcal/mol barrier to be overcome. Finally, the Na/H exchange between PhC3H6Na and (unreacted) toluene molecules proceeds through a 18 kcal/mol barrier and ca. 10 kcal/mol is released. The study has confirmed the basic alkylation scheme proposed by Pines, Vesely, and Ipatieff more than 50 years ago.