Thiobenzamide: Structure of a free molecule as studied by gas electron diffraction and quantum chemical calculations

The equilibrium (re) molecular structure of thiobenzamide along with r(h1) structure has been determined in gas phase using gas electron-diffraction (GED) at about 127 degrees C and quantum-chemical calculations (QC). Rovibrational distance corrections to the thermal averaged GED structure have been computed with anharmonic force constants obtained at the MP2/cc-pVTZ level of theory. According to the results of GED and QC thiobenzamide exists as mixture of two non-planar enantiomers of C-1 symmetry. The selected equilibrium geometrical parameters of thiobenzamide (r(e), angstrom and angle(e), deg) are the following: (C=S) = 1.641(4), (C-N) = 1.352(2), (C-C) = 1.478(9), (C=C)(av) = 1.395(2), CCN = 114.7(5), CCS = 123.4(5), C2C1C7S = 31(4), C6C1C7N = 29(4). The structure of thiobenzamide in the gas phase is markedly different to that in the literature for the single crystal. The differences between the gas and the solid structures are ascribed to the presence of intermolecular hydrogen bonding in the solid phase. (c) 2018 Elsevier B.V. All rights reserved.