A Molecular Orbital Treatment of Hydrogen Bonds. I. Preliminary Results

Abstract

Abstract 1) The changes caused by hydrogen bonds in the electronic structure of several molecules have been discussed by the use of the extended LCAO MO method. 2) The delocalization energy have been calculated to be 3.8 kcal./mol. 3) The frequency shifts in the ultraviolet spectrum cannot be explained. 4) In the formic acid dimer it has clearly been shown that the population transfers from the carbonyl group to the hydroxyl group and that a small bond population arises between them. 5) The 2pπ orbital on the hydrogen atom contributes almost nothing to the π delocalization energy. 6) The π hydrogen bond has also been discussed. 7) The defects in the extended LCAO MO method in treating molecules with polar groups or lone pairs have been pointed out, a method for improvement suggested, and some critical discussion of the present treatment added. The calculation was carried out on the IBM 7090 at the Japan IBM Co., with the permission of the UNICON Committee, whose kindnees we hereby acknowledge.