Experimental and theoretical studies of hydrogen bonding.
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Date
1995
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Abstract
The theoretical and experimental work in this thesis is primarily aimed at
i) the quantification of the strengths of a number of hydrogen bonded
systems, and ii) exploring the relationships that exist between the various
physico-chemical properties determined in this study, which are related to
the hydrogen bonding phenomenon.
To this end a three part study of some hydrogen bonded systems has been
undertaken. The study involves using a number of theoretical and
experimental procedures, including a theoretical ab initio molecular orbital
study, infrared spectroscopic determinations and a thermodynamic
investigation involving measuring enthalpies and volumes of mixing and
applying a theoretical model of interacting liquid mixtures.
Conclusions based on ab initio molecular orbital theory, thermodynamic and
infrared spectroscopic results conducted in this work include:
i) the proton donating ability of the three hydrogen donor moieties
studied in this work decreases in the order O-H > N-H ~ S-H,
ii) the proton accepting competence of the three electron donor atoms
considered in this work decreases in the order N > 0 > S in all cases
except in the liquid phase systems involving dipropylamine and
propane-1-thiol as proton donors, where the proton accepting ability
of the atoms is in the opposite order i.e. S > 0 > N, and
iii) a direct correlation exists between the shift in the A-H stretching
wavenumber and the hydrogen bond interaction energy.
. Although a number of factors influence the stability of the hydrogen bond,
it was also tentatively concluded that in liquid phase systems involving
weakly self-associated hydrogen bond donor molecules, the available surface
area of the proton accepting atom becomes the dominant strength
determining factor, otherwise factors such as basicity and electronegativity
dominate.
Description
Thesis (Ph.D.)-University of Natal, Durban, 1995
Keywords
Hydrogen bonding., Theses--Chemistry.