The molecular structure, conformation, force field and potential function to internal rotation of 2,2-dichloroacetamide as studied by quantum chemical calculations and gas electron diffraction data from photographic plates using a commercial scanner

A description of how we presently use a commercial scanner to obtain electron diffraction data from photographic plates is given. Compared to data previously obtained from a microdensitometer the R-factors and the derived standard deviations for the structure parameters were reduced with approximately 50%. Quantum chemical calculations have been made using HF, DFT and MP2 and the basis sets 6-311þþG** and Aug-cc-pVTZ. The calculations are not entirely consistent in their predictions. A syn-like conformation is determined experimentally. The dihedral angle H–C–CyO is about 18 degrees, i.e. the C–H bond is pointing towards the CyO bond. The most important structure parameters referred to a planar structure with Cs symmetry are: R(CyO) ¼ 1.223(4), R(C–N) ¼ 1.358(5), R(C–C) ¼ 1.538(6), R(C–Cl) ¼ 1.776(5), /OCN ¼ 125.1(5), /CCCl ¼ 110.8(3), /CCN ¼ 116.3(5) where distances are in A° and angles in degrees. Estimated error limits are three standard deviations from the least-squares refinement. The experimental results are esse2,2-Dichloroacetamide; Structure; Conformation; Potential to internal rotation; Quantum chemical calculations; Application commercial scannersntially in agreement with the quantum chemical calculations. q 2003 Elsevier B.V. All rights reserved.