Knowledge Bank

The rotational spectra of four isotopomers of the 1,1,2--trifluoroethylene-hydrogen fluoride complex (HF-CHFCF$2$, DF-CHFCF$2$, HF-$\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}$CHFCF$2$, and HF-CHF$\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}$CF$2$) have been collected in the 7--22 GHz region with a Fourier transform microwave spectrometer. The complexes are generated using pulsed jet expansion of a mixture of HF (or DF), CHFCF$2$, and Ar, and the two $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}$C-containing isotopomers are observed in natural abundance. Only $a$-type transitions are seen for all isotopomers, and for most lines in the DF-containing isotopomer, deuterium nuclear quadrupole hyperfine structure is not resolved within the experimental linewidth of 10--15 kHz. Both the Kraitchman substitution coordinates and the rotational constants are consistent with a planar structure in which a hydrogen bond is formed between H in HF and the F on C-2 in CHFCF$2$ with a secondary interaction between the H (geminal to the F involved in the hydrogen bond) in CHFCF$2$ and the F in HF.