STUDIES ON THE PRECIPITATION OF SOME PHOSPHATES AND CONFORMATIONS OF CYCLIC COMPOUNDS FROM X-RAY DIFFRACTION DATA
STUDIES ON THE PRECIPITATION OF SOME PHOSPHATES AND CONFORMATIONS OF CYCLIC COMPOUNDS FROM X-RAY DIFFRACTION DATA
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Date
1997
Authors
AJIBOLA , VICTOR OLATUNJI
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Abstract
In part I of the thesis, studies were carried out on
the precipitation of hydroxyapatite. A preliminary
experiment involving the preparation of calcium
hydroxyapatite (HAP) using three different sets of
starting materials was done. The crystallinity and
stoichiometry of the HAP were dependent on the starting
materials.
The precipitation of amorphous calcium phosphate
(ACP), and its transformation to HA? in the presence of
various compounds and ions have also been studied using
x-ray diffractometry. The nucleotides, AMP, ADP and ATP
(usually regarded as type II inhibitors) caused a slight
but discernible decrease in the mean size of the
apatitic crystals. However, citrate another type II
inhibitor did not appear to alter the mean cryst
size in agreement with literature. It would appear that
the effect an inhibitor has on the resultant apatitic
crystal is dependent on the mechanism of inhibition and
not necessarily on whether it is a type I or type II
inhibitor. Results obtained for casein and L-glutamate
shows that they may be regarded as type II inhibitors.
Tetracycline, a broad spectrum antibiotic which may also
be classified as type II inhibitor, caused a slight
decrease in the mean size of the apatitic crystals Inhibition by this compound seems to be more as a result
of steric hinderance rather than attachment to the active
site of the HAP nuclei.
Preparation of tin hydroxyapatite was attempted using
hydrateci cin (II) oxide as the starting material. To the
best of our knowledge, a new tin (II) phosphate was
obtained which has strong similarit; 3 with calcium
hydroxyapatite (HAP) . This new tin (II) phosphate gave
a molybdenum blue colouration due to the reduction f
molybdophosphoric acid during phosphate determination,
indicating that tin existed in the +2 oxidation state.
X-ray diffraction patterns of the products obtained in
the attempted preparation of tin calcium hydroxyapatite
by aqueous and solid state reactions were obtained.
Precipitation from aqueous system containing 3 atom % tin
in solution gave product which is essentially featureless
and characteristic of amorpnous compounds, in agreement
with literature. At tin concentration significantly
greater than 20 atom %, the products of solid state
reaction at both 500° and 700°C were amorphous.
In part II of the thesis, the conformations adopted
by some ring compounds in the solid state are describe,
and parameterized. The effects of the molecular
environment on the geometry and conformation of the rings,
have been elucidated based on x-ray diffraction
structural data.
For cycloheptane ring derivatives, the boat
Description
A Thesis Submitted to the postgraduate School,
Ahmadu Bello University, Zaria.
In Partial Fulfilment of the Requirements for the
Degree of Doctor of Philosophy in Chemistry.
Department of Chemistry
Faculty of Science
Ahmadu Bello University
Zaria, Nigeria.
Keywords
STUDIES,, PRECIPITATION,, PHOSPHATES,, CONFORMATIONS,, CYCLIC COMPOUNDS,, X-RAY DIFFRACTION DATA,