AB-INITIO CALCULATIONS OF PYRIDINE AND ITS 2-CHLORODERIVATIVES AND 3-CHLORODERIVATIVES

Ab initio calculations of the C5H5N, 2-, and 3-ClC5H4N molecules by th e RHF method in the valence split 6-31G basis set with full optimizat ion of the geometry have been carried out. The alternation of the char ges on the atoms of the pyridine ring and of the populations of their p(x)-orbitals is in agreement with the noninductive through-the-field interaction of the geminal atoms. The Cl-35 NQR frequencies and the el ectric field gradient asymmetry parameters at the Cl-35 nuclei in 2- a nd 3-ClC5H4N were estimated using the populations of the valent p-orbi tals of the CI atoms and their components. The Cl-35 NQR frequency for the first compound is lower than that for the second one, mainly due to the higher p(sigma)-electron population of its Cl atom.