Electronic structure of planar-quasicycled organic molecules with intramolecular hydrogen bond

By means of the HF/6-311G(d,p) method, the electronic structure of the series of organic molecules, among which are malonaldehyde, acetylacetone, thiomalonaldehyde, the derivatives of aniline 2-XC6H4NH2, phenol 2-XC6H4OH, benzenethiol 2-XC6H4SH (X = CHO, COOH, COO-, NO, NO2, OH, OCH3, SH, SCH3, F, Cl, Br), 8-hydroxyquinoline, 8-mercaptoquinoline, tropolone, has been studied. The intramolecular hydrogen bond (IHB) has been established to lead to a local electron redistribution in quasicycle, and primarily to the electron density transfer between the direct IHB participants - from the hydrogen atom toward the proton-aceptor atom. On forming the IHB of the S-H center dot center dot center dot O type, the electron density in gcneral decreases on the sulphohydryl hydrogen atom and increases on the sulphur atom.