Study of hydrogen bondings in phenol-amine adducts
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Date
2008-05
Authors
Rosli, Mohd Mustaqim
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Abstract
Five samples have been prepared to study the phase transition caused by
hydrogen bonds III phenol-amine adducts. Those samples are (1) 2-
Methylquinolinium 2,4-dinitrobenzoate, (II) the 1: 1 adduct of 3,5-dinitrobenzoic acid
and quinoline, (III) Hexamethylenetetraminium 2,4-dinitrobenzoate monohydrate,
(IV) 4-Aza-l-azoniabicyclo[2.2.2]octane 2,4-dinitrobenzoate and (V)
Hexamethylenetetraminium 3,5-dinitrobenzoate hemihydrate. Single crystal X-ray
crystallography method has been used to determine whether there are any changes in
lattice parameters at room temperature and lOOK.
A number of hydrogen bonds were observed in all the samples. However only
sample (V) showed a phase transition phenomena in which different lattice parameter
values were observed at room temperature and lOOK (doubling the c-axis value). For
sample (V), temperature dependence studies were done to find the critical
temperature Te. From the result, we know that this is a first order phase transition
where the changes of the unit cell parameters occur discontinuously at the transition
temperature Te = 129K. This first order case is also explained macroscopically using
Landau phenomenological theory.
An alternative method of calculating the thermodynamic properties of a
system with the second-order phase transition caused by interaction of hydrogen
bonds and phonon of the crystal was also done in this study. This was carried out by
separating out the pseudo-spin variables completely and using only pseudo-spin
variables when calculating the free energy. The results agree with the previous
published results.
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Keywords
The phase transition caused by hydrogen bonds , III phenol-amine adducts.