Microwave spectrum and molecular structure of g a u c h e-1,2-difluoroethane

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Abstract
The microwave spectra of four isotopic species of gauche‐1,2‐difluoroethane have been observed. Having combined the rotational constants obtained with those of the normal species, all the structural parameters have been determined as follows; r(C–C)=1.493(8) Å, r(C–F) =1.390(3) Å, r(C–Hg)=1.099(2) Å, r(C–Ht)=1.093(5) Å, ∠CCF=110.6(5)°, ∠CCHg=108.4(6)°, ∠CCHt=111.3(6)°, ∠HCH=109.1(5)°, ∠FCHg=109.6(3)°, ∠FCHt=107.8(6)°, and FCCF (dihedral angle)=71.0(3)°. The spectra of normal species in the excited torsional states have also been observed up to vt=4, and the results of the analysis indicate that the gauche‐gauche barrier should be higher than the value, 468.6 cm−1, reported by the analysis of vibrational spectra.