Conformations of trimethoxymethane: Matrix isolation infrared and ab initio studies

Conformations of trimethoxymethane (TMM) were studied using matrix isolation infrared spectroscopy and ab initio computations performed at the HF and B3LYP levels, using a 6-31++G∗∗ basis set. Computationally, six minima were identified on the potential surface, of which the conformer with the C1(TG±G±) structure corresponded to the ground state. The features in the matrix isolation infrared spectra could be assigned to this ground state conformer, which was supported by frequency calculations at the B3LYP level. Hot nozzle experiments indicated the possibility that the structures with C3(G±G±G±) and Cs(TG+G−) geometries, which were the next two higher energy conformers above the ground state structure, may also have been populated in the Ar matrix, though only to a small extent. The barrier for conformer interconversion from these higher energy conformers to the ground state geometry, C3(G±G±G±) → C1(TG±G±) and Cs(TG+G−) → C1(TG±G±), were computed to be 2.94 and 1.39 kcal/mol, respectively.