Molecular structure and conformation of phenylacetyl chloride as obtained by gas-phase electron diffraction and theoretical calculations

作者：Aarset Kirsten^*; Hagen Kolbjorn

来源：Journal of Molecular Structure, 2008, 892(1-3): 373-377.

DOI：10.1016/j.molstruc.2008.06.001

• Structure
• Gas-phase electron diffraction
• Theoretical calculations
• Phenylacetyl chloride

The structure and conformation of phenylacetyl chloride, PhCH(2)-(C=O)Cl, has been determined by gas-phase electron diffraction (GED), using results from ab initio calculations (HF and MP2/6-311+G(d,p)) to obtain restraints on some of the structural parameters. The molecules exist in the gas-phase (118 degrees C) as a mixture of two stable conformers; syn with C=O eclipsing C(alkyl)-C(phenyl) and gauche with C=O eclipsing C-H. For both conformers the phenyl ring is about 90-120 degrees out of the plane of the acetyl group. The experimentally observed conformational composition was 75(8)% gauche and 25(8)% syn (parenthesised values are 2 sigma). Using theoretical Values for the entropy difference between conformers, including the fact that there are two identical gauche forms, this composition corresponds to an enthalpy difference of Delta H degrees(gauche-syn) = -0.8(12) kJ mol(-1). The results for the principal distances (r(a)) and angles (angle(h1)) for the gauche conformer obtained from the combined GED/ab initio study (2 sigma uncertainties) are: r(C-H)(phenyl) = 1.078(6) angstrom, r(C-H)(alkyl) = 1.089(12) angstrom, r(C=O) = 1.180(6) angstrom, r(C-C)(phenyl) = 1,396(4) angstrom (average value), r(C(phenyl)-C(alkyl)) = 1.509(16) angstrom, r(C(alkyl)-C(carbonyl)) = 1.513(12) angstrom, r(C-Cl) = 1.780(6) angstrom, angle C(phenyl)-C(alkyl)-C(carbonyl) = 110.6(12)degrees, angle C-C=O = 125.5(8)degrees, angle C-C-Cl = 113.3(6)degrees, angle C-C-H(phenyl) = 19.9(2)degrees (average value), angle C(phenyl)-C(alkyl)- H = 110.8(2)degrees (average value), phi(C-C-C-C) = 118(4)degrees, phi(C-C-C=O) = 95(2)degrees.

• 出版日期2008-12-15