The C−F···H−O Hydrogen Bond in the Gas Phase. Rotational Spectrum and ab Initio Calculations of Difluoromethane-Water

Abstract

The free jet millimeter wave spectra of four isotopomers of the 1:1 complex between difluoromethane and water have been observed and assigned. The water molecule lies in the FCF plane of difluoromethane, linked through an O−H···F hydrogen bond to one fluorine atom, and entgegen to the second one. The H bond parameters are r(F···H) = 2.20 Å, ∠(F···H−O) ≅ 135°, and ∠(C−F···H) ≅ 93°, respectively. The oxygen is zusammen to the C atom, and the “free” water hydrogen is entgegen to the difluoromethane moiety. The value of 90° of the C−F···H angle is indicative of the preservation of the p character of the lone pairs of fluorine in the adduct.