The structure and conformation of dichloroacetyl chloride as determined by gas-phase electron diffraction

The structure and conformation of dichloroacetyl chloride have been determined by gas-phase electron diffraction at nozzle temperatures of 20 and 119°C. The molecules exist as a mixture of two conformers with the hydrogen and oxygen atoms syn and gauche to each other. The composition (mole fraction of syn form) of the vapor was found to be 0.72 ± 0.06 and 0.73 ± 0.12 at 20 and 119°C, respectively, corresponding to almost equal energy for the two forms. The results for the distance (r_g), angle ∠α and r.m.s. amplitude (l) parameters obtained at the two temperatures are entirely consistent. At 20°C the more important parameters, with estimated uncertainties of 3σ are: r(C-H) = 1.062(0.049)Å, r(C0) = 1.189(0.003)Å, r(C-C) = 1.535(0.008)Å, r(CO-Cl) = 1.752 (0.009)Å, r(CHCl-Cl) = 1.771(0.004)Å, ∠C-CO = 123.3(1.3)°, ∠C-CO-Cl = 113.9 (5.9)°, ∠C-CHCl—Cl = 109.5(1.5)°, ∠C1-C-Cl = 111.7(0.5)°, ∠Cl-C-H = 108.0(1.5), φ₁ (HCCO torsion angle in the syn conformer) = 0.0° (assumed), φ₂ (HCCO torsion angle in the gauche conformer) = 138.2(5.1)°.