Spectroscopical and electron diffraction studies of some unsaturated chlorohydrocarbons

Detta är en avhandling från Stockholm : Stockholm University

Sammanfattning: This thesis deals with structural properties of unsaturated chlorhydrocarbons of general formulas C^H^Cl, C^H^Cl and as studied by microwave spectroscopy, electron diffraction and vibrational spectroscopic methods. The two former methods both give values of molecular structure parameters in gas phase, but due to different averages of the thermal motion the structures arrived at are not comparable. The link between the different structures is provided for by a reliable force field, derived from the observed fundamental vibrational energy transitions, on which the emphasis of this work lies.The vibrational spectra of cis- and trans-monochlorobutadiene, cis, cis-, cis.trans- and trans,trans-dichlorobutadiene and of 4-chlorobuten- 3-yne were recorded in the medium and far infrared region and in Raman.Assignment of the spectra was possible. Band contours of the spectra in the gaseous state as well as Raman polarization data were taken into account. Normal coordinate analyses were carried out with the help of a computer program, in which the estimated force field of the simplified valence type of each molecule, constructed of parameter values from similar molecules, is fitted to the observed frequencies. For the monochlorobutadienes, force fields of 22 diagonal and 8 off-diagonal elements, of which 17 values were kept fixed, succeeded in reproducing the observed fundamental frequencies. For the disubstituted butadienes, force fields of 29 parameters, 7 of which off-diagonal, were employed. Root-mean-square amplitudes of vibration and perpendicular amplitude correction coefficients for subsequent use in the refinement of electron diffraction data were also calculated.In the chlorobutenyne case, the force field consisted of 27 parameters, 10 off-diagonal elements. The agreement between the observed frequencies and those calculated with the force field was very good.

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