Conformations of 1,1-diethoxyethane: A matrix isolation infrared and ab initio study

Conformations of 1,1-diethoxyethane (DEE) were studied using matrix isolation infrared spectroscopy. Infrared features of the lowest energy, G∓G±(tt) conformer and the first higher energy, TG−(tt) conformer of matrix-isolated DEE were observed for the first time. The experiments were supported by ab initio computations performed at the HF and B3LYP levels, using a 6-31++G** basis set. The computed vibrational wavenumbers at the B3LYP/6-31++G** level for the G∓G±(tt) and TG−(tt) conformers, were found to agree well with the experimentally observed features, leading to a definitive assignment of the infrared features of these conformers of DEE. At the B3LYP/6-31++G** level, the energy of TG−(tt) conformer was found to be 0.42 kcal/mol above the ground state G∓G±(tt) conformer. AIM calculations were also performed to understand the role of intramolecular CH⋯O interaction in the conformational preferences in DEE.