The molecular structure of fumaric acid and the deformation of carboxyl group geometry on crystallization |
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Authors: | JL Derissen |
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Institution: | General Chemistry Department, Section Structural Chemistry, Rijksuniversiteit Utrecht, Padualaan 8, UtrechtThe Netherlands |
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Abstract: | The molecular structure of fumaric acid was studied by means of gas electron diffraction at 260° C. The molecular parameters and their standard deviations obtained for a C2h model are (ra distances in Å, angles in degrees): CO: 1.202(0.002), C-O: 1.341(0.006), C-C: 1.486(0.004), CC: 1.356(0.016). C-C-O: 112.1(1.0), C-CO: 124.4(1.1), C-CC: 121.8(1.2). From the available data on carboxylic acids the weighted average deformation of the structure of a carboxylic group on crystallization was determined; a significant expansion of the O-H bond (0.040 Å ), the CO bond (0.010 Å ) and the C-C-O bond angle (1.5° ) and a shrinkage of the C-O bond (0.041 Å ), the Cα-C bond (0.012 Å ) and the C-CO bond angle (2.0° ) was found. The energy for these deformations was estimated to be 1.8 kcal mol?1. |
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