Conformational analysis of 1,2-dimethoxyethane by ab initio molecular orbital and molecular mechanics calculations: stabilization of the TGG' rotamer by the 1,5 CH3/O nonbonding attractive interaction

Ab initio molecular orbital calculations at the MP3/6-311+G * //HF /6-311+G * level show that relative energics of TTT, TGT, TTG, GTG, GTG', TGG, TGG', GGG, and GGG' rotamers of 1,2-dimethoxyethane are 0.0, 0.51, 1.65, 3.47, 3.34, 2.24, 0.53, 1.97, and 2.30 kcal/mol, respectively. Populations of rotamers predicted from calculated ΔG's at 273. 15 K agree satisfactorily with the gas-phase electron diffraction results reported by Astrup