Shape of the Adduct Formic Acid–Dimethyl Ether: A Rotational Study

Formic acid and dimethyl ether are combined in a supersonic expansion to form a molecular adduct with the two subunits held together by a “classical” OH···O hydrogen bond and a bifurcated weak CH₂···O hydrogen bond. The rotational spectra of the parent and of two ¹³C isotopologues in natural abundance show that the complex has C_s symmetry, with the heavy atom symmetry planes of HCOOH and (CH₃)₂O perpendicular to each other.