Studies on natural Raman optical activity

Escribano Rivero, Juan Ricardo (1985) Studies on natural Raman optical activity. PhD thesis, University of Glasgow.

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Optical activity associated with vibrations of
chiral molecules can provide much stereochemical
information. There are two techniques which observe
vibrational optical activity (VOA), namely: infrared
circular dichroism (IRCD) and vibrational Raman optical
activity (VROA). The first, IRCD, is an extension of
circular dichroism into the infrared and measures a
difference in absorbance of incident left and right
circularly polarized infrared radiation. VROA is
concerned with a difference in the intensity of Raman
scattering when the chiral system is illuminated with
left and right circularly polarized radiation. Recent
reviews that cover both techniques are in the references
of the Summary.
This thesis is divided into two main parts. The
first (Chapters 1 to 4) is concerned with theoretical
studies of ROA. The second (Chapters 5 to 8) with
calculations of the observable parameters in VROA and
their comparison with experimental results.
Chapter 1 comprises a theoretical study in molecular
scattering tensors: one significant new result was the
discovery of a Stokes-antiStokes asymmetry in the ROA
observables. In Chapter 2 is reviewed the experimental
conditions in which VROA experiments have been carried
out and how the artifacts will affect their spectra. For
this, firstly, it has been necessary to provide a general
extension of the established equations which give the ROA
observables at any point in space. Subsequently a new and
more realistic parameter in ROA is defined in terms of
power. The difference with the original one is not
important in the experimental conditions in which the
spectra are recorded, but it is relevant from the
scientific aesthetic point of view. Particular cases are
derived from these general equations in total agreement
with the original and well established ones. In all cases
the influence of artifacts coming from imperfectly
modulated right and left circularly polarized incident
light has been considered. Chapter 3 is a generalization
of the "two group model" in VROA using the bond
polarizability theory. The model has been extended to
include deformations of non-axially symmetric groups. A
general critical revision of these formulae is provided.
Chapter 4 is a survey of miscellanea in VROA. An
interesting prediction is given in the case of Fermi
resonance. At the end of this chapter a new selection
rule is proposed in VROA which relates polarized and
depolarized VROA spectra. This rule is analogous to that
which relates polarized and depolarized conventional
Raman spectra.
The second part of the thesis is devoted to
calculations of the observable parameters in VROA and
their comparison with the experimental results. The
molecule CBrC1FH has not yet been studied experimentally
but it is a good (Chapter 5) example for calculations
because the results can be compared with those from other
theories such as the "atom dipole interaction model".
Chapter 6 treats another easy chiral molecule,
epoxypropane. The advantage of this molecule is that it
can be tested with its experimental spectrum and
considering the approximate force field we can say that
the comparison is good. Chapters 7 and 8 deal with small
chiral molecules derived from cyclohexanone, deuterated
and methylated.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Subjects: Q Science > QD Chemistry
Colleges/Schools: College of Science and Engineering > School of Chemistry
Supervisor's Name: Supervisor, not known
Date of Award: 1985
Depositing User: Adam Swann
Unique ID: glathesis:1985-8690
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 23 Jan 2018 10:07
Last Modified: 23 Jan 2018 10:07

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