Molecular structure of n-butane: calculation of vibrational shrinkages and an electron diffraction re-investigation

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 (+/- 3[sigma] ): rg(C-C) = 1.531(2)A, rg(C-H)= 1.117(5)A, [angle]CCC (trans. gauche average) = 113.8(4)[deg], [angle]CCH (ave) = 111.0(5)[deg] , gauche CCCC dihedral angle 65(6)[deg], % trans CONFORMER = 54 +/- 9%, and [Delta]G[deg] (gauche-- trans) = 497 +/- 220 cal mol-1.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22926/1/0000492.pd