A THEORETICAL AND EXPERIMENTAL-STUDY OF THE MOLECULAR-STRUCTURE OF 1-BUTYNE

The molecular structure of 1-butyne has been determined by gas electro n diffraction (GED) and by theoretical ab initio calculations at the M P2 level and with a 6-311G* basis set. The vibrational amplitudes and perpendicular amplitude corrections have been calculated based on a f orce field originating from the ab initio calculations and scaled to o bserved vibrational frequencies available from the literature. The mos t important structure parameters obtained from the GED study an the fo llowing (standard deviations in parentheses): r(a)(C=C) = 1.217(1) Ang strom; r(a)(=C-C) = 1.457(3) Angstrom; r(a)(C-3-C-4) = 1.544(4) Angstr om, angle=C-C-C = 111.9(4)degrees.