Force constants and equilibrium geometries in H 2O 2 and other small molecules containing an OH group

Abstract

General harmonic ab initio and semi-empirical force fields have been established for hydrogen peroxide and hypofluorous acid. Previous experimental force fields for H2O2 are unreliable due to the lack of sufficient experimental data for gaseous H2O2 and isotopic derivates.Harmonic and some anharmonic force constants are compared in a series of XOH compounds with X standing for H, H3C, H2N, HO and F. In this sequence,the OH stretching force constant frr decreases while the XOH bending force constant increases. There is a noticeable opposite trend for fRα (increasing) and fRα (decreasing) with the sum fRα + frα being almost constant. This effect maybe simulated by a simple model. The stretch-stretch coupling constant frR is always small and negative.The calculated OH bond lenghts are in very good agreement with available experimental values and support the previously assumed value of 0.965 A for H2O2. Bond angles are reproduced within an accuracy of 1 to 2 degrees.