The reaction between aluminium and dimethyl ether Comparative study of density functional theory and EPR results

Stationary points on the surface describing the reaction between aluminium and dimethyl ether (DME) have been located using density functional theory at the B3LYP level with a 6-31G(d,p) basis set. Hyperfine coupling constants (HFCC) of Al and the proton attached to it, as well as total energies, were computed at all stable structures using the B3LYP and BP86 functionals and the 6-311+G(2df,p) basis. Compared to earlier theoretical studies, additional stable conformers have been identified. An initial addition complex is formed between Al and CH3OCH3, located 4–9 kcal mol−1 below the free reactants in energy, depending on computational method. A first transition state connects the addition complex with a structure in which one hydrogen has migrated to the Al atom, whereafter a more stable C–H insertion structure is reached through a second transition state. A second reaction path leading to two C–O insertion products, starting from the addition complex, is also described. The most stable products are the cis and trans conformers of an open chain C–O insertion product which lie 58–65 kcal mol−1 below the reactants in energy. Among the C–H insertion products the most stable ones are cyclic cis and trans structures, which are found to lie 9–10 kcal mol−1 below the reactants.