Bonding between nonbonded sulfur and oxygen atoms in selected organic molecules (a quantum chemical study)

Abstract

A series of model compounds capable of intramolecular sulfur(II)-oxygen interaction of the 1,5-type was investigated by the ab initio SCF-MO method. Compounds of the type X-S-A=B-Y(Z)=O with cis configuration about A=B, containing X = F, OH, NH/sub 2/, CH/sub 3/, and SH; A = CH; B = CH and N; and Z = H, O, as well as lone pair, were studied. This results in four families containing a total of twenty compounds. The geometries of two basic planar conformations of these compounds, s-cis/s-trans (CT) and s-trans/s-trans (TT), obtained by internal rotations about the B-Y and S-C bonds, respectively, were optimized by using three different basis sets. These energy minimum conformations represent optimum geometries with and without S...O interactions, respectively. Four quantities were used to measure the extent of S...O interactions. These included the lengthening of the Y-O bond on going from TT to CT (..delta..R(Y-O)), the shortening of the S...O distance (..delta..R(S...O)), the energy change between TT and CT (..delta..E(S...O)), and the Mayer type bond order in the CT conformations (B(S...O)). The linear interdependence of these four quantities indicated that each of these four parameters was about equally good measure of the extent of S...O interaction. With the aidmore » of these numerical measures earlier qualitative principles may now be evaluated quantitatively.« less