Electron diffraction and quantum chemical study of the molecular structureof para-methylbenzenesulfonyl fluoride and para-methylbenzenesulfonyl bromide

A combined electron diffraction and mass-spectrometric experiment has been performed at 350(2) and 340(2) K, respectively to study the molecular struc ture a of para-methylbenzenesulfonyl flouride and para-methylbenzelzesulfon yl bromide. The electron diffraction data are analyzed in terms of r(alpha) structure. Several geometrical models with different orientations of the s ulfonyl halide group relative to the plane of the benzene ring are consider ed. The angle between the plane of the benzene ring and the plane of the S- Hal band equals 90 degrees indicating that the molecules have C-S symmetry. The structural parameters of the molecules and the internal rotation barri ers of the sulfonyl halide and methyl groups have been calculated by the ab initio and semiempirical quantum chemical methods. The results of calculat ions are compared with electron diffraction data.