K. Hagen, Q. Shen, R. Carter
Apr 1, 2002
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Abstract
The molecular structure and conformational composition of 1,1-dichloro-2-propanone (1,1-dichloroacetone) have been investigated by gas-phase electron diffraction at 60 °C. Results from ab initio molecular orbital calculations were used as constraints in the analysis. The experimental data are consistent with a model where the molecules exist predominantly with the hydrogen synperiplanar to the carbonyl group. Small amounts (up to 15%) of a second anticlinal form (C−Cl eclipsing CO) cannot be ruled out. Ab initio calculations showed that both synperiplanar and anticlinal forms are stable conformers with the former conformer lower in energy by 2.25 kcal mol-1 (MP2/6-311+G(d)). The geometrical parameters for the synperiplanar conformer (rg and ∠α) obtained from least squares analyses of the electron diffraction data, using results from the theoretical calculations to provide some constraints in the model used, are r(C−H)av = 1.093(14) A (average value), r(CO) = 1.196(6) A, r(C1−C2) = 1.524(4) A, r(C2−C3) = 1...