A theoretical and experimental study of the molecular structure of 1-butyne

Abstract The molecular structure of 1-butyne has been determined by gas electron diffraction (GED) and by theoretical ab initio calculations at the MP2 level and with a 6-311G∗∗ basis set. The vibrational amplitudes and perpendicular amplitude corrections have been calculated based on a force field originating from the ab initio calculations and scaled to observed vibrational frequencies available from the literature. The most important structure parameters obtained from the GED study are the following (standard deviations in parentheses): r a ( C  C ) = 1.217(1) A ; r a ( C  C ) = 1.457(3) A ; r a ( C 3  C 4 ) = 1.544(4) A ; ∠CCC = 111.9(4)°.