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

Abstract

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 6-311++G** 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–CO is about 18 degrees, i.e. the C–H bond is pointing towards the CO bond. The most important structure parameters referred to a planar structure with C s symmetry are: R(CO)=1.223(4), R(C–N)=1.358(5), R(C–C)=1.538(6), R(C–Cl)=1.776(5), ∠OCN=125.1(5), ∠CCCl=110.8(3), ∠CCN=116.3(5) where distances are in Å and angles in degrees. Estimated error limits are three standard deviations from the least-squares refinement. The experimental results are essentially in agreement with the quantum chemical calculations.