Abstract:
TITLE: The normal co-ordinate analysis, vibrational spectra and
theoretical infrared intensities of some thiocarbonyl halides.
AUTHOR: J. L. Brema
SUPERVISOR: Dr. D. C. Moule
NUMBER OF PAGES: 89
ABSTRACT: The vibrational assignment of the five-in-plane fundamental
modes of CSClBr has been made on the basis of infrared gas phase
and liquid Raman spectral analyses to supplement our earlier
vibrational studies. Even though the one out-of-plane fundamental
was not observed spectroscopically an attempt has been
made to predict its frequency. The vibrational spectra contained
impurity bands and the CSClBr assignment was made only after a
thorough analysis of the impurities themselves.
A normal co-ordinate analysis calculation was performed
assuming a Urey-Bradley force field. This calculation yielded
the fundamental frequencies in good agreement with those observed
after refinement of the originally transferred force constants.
The theoretical frequencies are the eigenvalues of the secular
equation and the calculation also gave the corresponding
eigenvectors in the form of the very important LLj matrix. The
[l] matrix is the transfoirmation between internal co-ordinates
and normal co-ordinates and it is essential for Franck-Condon
calculations on electronically excited molecules and for infrared
Integrated band intensity studies.
Using a self-consistent molecular orbital calculation
termed "complete neglect of differential overlap" (CNDO/2) ,
theoretical values of equilibrium bond lengths and angleswere calcuted for a series of carbonyl and thlocarbonyl
molecules. From these calculations valence force field force
constants were also determined but with limited success.
With the CNIX)/2 method theoretical dipole moment derivatives
with respect to symmetrized internal co-ordinates were calculated
and the results should be useful in a correlation with experimentally
determined values.
