Noncovalent Interactions and Internal Dynamics in Dimethoxymethane-Water

The millimeter-wave absorption and Fourier transform microwave spectra of five isotopologues of the 1:1 adduct dimethoxymethane-water have been measured in supersonic expansions. Each rotational transition appears as a quintuplet, due to the internal rotation of the two methyl groups, which are non-equivalent in the adduct. The water moiety, linked asymmetrically to dimethoxymethane, behaves as a proton donor to one of its oxygen atoms and interferes with the internal rotation of the farther methyl group through a C-HO interaction. From the analysis of the observed splittings, the V3 barriers to the internal rotation of the two methyl groups have been determined to be 6.83(8) and 6.19(8) kJ/mol, respectively. The hydrogen bond structural parameters have been determined, the O-HO and C-HO distances being 1.93(1) and 2.78(4) Å, respectively.