Molecular structure and internal rotation of CH2Cl group of chloropropanone oxime: gas electron diffraction, microwave spectroscopy, and quantum chemical calculation studies

The molecular structure of chloropropanone oxime [ClCH 2 C(CH 3 )=NOH] has been determined by gas electron diffraction (GED), microwave spectroscopy (MW) and quantum chemical calculations. Potential energy curves for the internal rotation of CH 2 Cl group in ( E )- and ( Z )-isomers as well as the optimized geometries and force constants for four conformations have been calculated by the quantum chemical calculations. Combined data analysis of the GED and MW data revealed the conformational mixture of 68(4) % ( E )- anticlinal and 32 % ( Z )- synclinal conformers. The principal values of geometrical parameters of the E- anticlinal conformer are: r g (ClH 2 C–C) = 1.499(2) Å, r g (C–CH 3 ) = 1.503(2) Å, r g (C=N) = 1.276(4) Å, r g (C–Cl) = 1.805(3) Å, r g (N–O) = 1.398(4) Å, ∠ α C–C=N = 113.2(16)°, ∠ α C–C–Cl = 111.1°(5), ∠ α H 3 C–C=N = 127.0°(13), ϕ (NCCCl) = 121.1°(21). Numbers in parentheses are three times standard deviations of the data fit.