Spectroscopic investigations of hydrogen bonding interactions in the gas phase. V.t The identification and determination of the geometry and electric dipole moment of the hydrogen bonded heterodimer formed between oxirane and hydrogen fluoride, (CH 2 ) 2 O • • • HF, by infrared and microwave spectroscopy

Abstract

The hydrogen bonded heterodimer formed between oxirane and hydrogen fluoride has been identified through its infrared and microwave spectra. Rotational constants/MHz and centrifugal distortion constants/kHz for the following isotopic varieties have been derived from an analysis of the rotational spectra in the vibrational ground state: A B A (CH 2 ) 2 160* • -HF 16099 3638.75 3462.31 15.3 25.8 (CH2)2160- • *DF 15984 3605.66 3434.85 14.1 20.9 For the species (CH2)2180 • • • HF only the rotational constants 7059.7 MHz and B — C = 135 MHz could be obtained. It is established from arguments based on Pband A that the dimer has a pyramidal configuration at the oxygen atom and that the molecular point group is (7g. If the justifiable assumption is made that the monomer geometries are unchanged on dimer formation, then the observed rotational constants for (CH 2 )2160* • -H F leadtor0(O* • *F) = 2.627 A ja n d ^ = 71.8°, where ^ is the angle between the plane of the three-membered ring and the H—F direction. Replacement of H by D in the hydrogen bond does not significantly change these values.