A theoretical study of ROX (R = H, CH3;: X = F, Cl, Br) enthalpies of formation, ionization potentials and fluoride affinities

We report the results of a systematic Gaussian2 ab initio study of the ROX (R = H, CH3; X = F, Cl, Br) series. The calculated standard enthalpies of formation (Delta H-f(298K)) provide the following estimates for the previously undetermined R = CH3 series; Delta H-f = - 94.9, - 74.0, and - 57.0 kJ mol(-1) for X = F, Cl, and Br, respectively. The calculated ionization potentials (IP) provide an estimate of 10.24 eV for the previously undetermined IP of CH3OBr. The first determination of fluoride affinities for ROX species are presented and are shown to depend strongly on the orientation of the F-+ ROX complex and on the identity of the halogen substituent. (C) 1999 Elsevier Science B.V. All rights reserved.