Cis-1-chloro-3-fluoropropene: gas phase molecular structure and conformation as determined by electron diffraction

Abstract

Gaseous cis-1-chloro-3-fluoropropene has been investigated at 20°C by electron diffraction. Only one conformer was observed, but small amounts (<10%) of a second form could not be excluded. The average CCCF torsional angle (τ) was found to be τ = 149(4), where τ = 0° corresponds to the fluorine atom eclipsing the carboncarbon double bond. The potential function for the torsion about the CC bond could be approximated by v(φ) = V 0 (1 + (φ/φ 0) 4−2(φ/φ 0) 2), φ = 180 — τ, with φ 0 = 37(10)° and V 0 = 1.0(1.0) kJ mol −1. The results for bond lenghts ( r a) and bond angles (∠ α) are as follows: r(CC) = 1.347(14) Å, r(CC) = 1.493(14) Å, r(CCl) = 1.737(5) Å, r(CF) = 1.388(9) Å, ∠CCC = 125.4(8)°, ∠CCCl = 122.7(6)°, ∠CCF = 111.2(8)°. The quoted error limits are 2 σ, where σ includes uncertainties in the voltage and nozzle-to-plate distances and corrections for correlation in the experimental data.