Molecular structure of n-butane: calculation of vibrational shrinkages and an electron diffraction re-investigation |
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Authors: | WF Bradford Susan Fitzwater LS Bartell |
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Institution: | Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109 U.S.A. |
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Abstract: | A normal coordinate analysis was carried out based on the force field of Schachtschneider and Snyder in order to calculate all amplitudes of vibration and shrinkage corrections for n-butane. The results are tabulated to aid diffraction analyses of related substances. A vapor-phase electron diffraction reinvestigation of n-butane led to experimental measurements of the principal amplitudes of vibration and to the following molecular parameters (± 3σ ): rg(C-C) = 1.531(2)Å, rg(C-H)= 1.117(5)Å, ∠CCC (trans. gauche average) = 113.8(4)°, ∠CCH (ave) = 111.0(5)° , gauche CCCC dihedral angle 65(6)°, % trans conformer = 54 ± 9%, and ΔG° (gauche— trans) = 497 ± 220 cal mol?1. |
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