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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 higherenergy 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 TGconformers 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** level, the energy difference between the G -G + and TGconformers was computed to be 0.67 kcal/mol.

The (1:1) clusters of 1,2,4,5-tetrafluorobenzene (TFB) with methanol and with 2,2,2-trifluoroethanol (TFE) were studied both experimentally and computationally. Through use of fluorescence-detected infrared spectroscopy, the (1:1) clusters were identified in supersonic jets. Intermolecular interactions in the clusters were characterized by the spectral shifts of the aromatic C-H stretching modes in the TFB moiety owing to the cluster formation. The molecular structures, stabilization energies, and vibrational frequencies of the clusters were computed at the MP2/6-31+G level. Both computational and experimental data indicate that an aromatic C-H...O hydrogen bond is present in the TFB-methanol cluster, while it is absent in the TFB-TFE cluster.