Conformations of 1,1-Dimethoxyethane: Matrix Isolation Infrared and ab Initio Studies

Abstract

Conformations of 1,1-dimethoxyethane (DME) were studied using matrix isolation infrared spectroscopy. DME was trapped in an argon matrix using an effusive source maintained at temperatures over the range 298−431 K. Deposition was also done using a supersonic jet source to look for conformational cooling in the expansion process. As a result of these experiments, infrared spectra of the ground and first higher-energy conformer of DME are reported for the first time. The experimental studies were supported by ab initio computations performed at HF and B3LYP levels, using a 6-31++G** basis set. Computationally, five minima were identified corresponding to conformers with G-G+, TG-, TG+, TT, and G+G+ structures, given in order of increasing energy. The computed frequencies at the B3LYP level for the G-G+ and TG- conformers were found to compare well with the experimental matrix isolation frequencies, leading to a definitive assignment of the infrared features of DME for these conformers. At the B3LYP/6-31++G*...