New Group Contribution Method for Predicting the Critical Pressures of Fatty Acids and Triglycerides
Charles Otobrise,
Kenneth Osondu Monago
Issue:
Volume 3, Issue 6, November 2015
Pages:
45-49
Received:
9 October 2015
Accepted:
21 October 2015
Published:
30 October 2015
Abstract: A new and useful method for evaluating and predicting the critical pressures (Pc) of n-fatty acids and triglycerides was developed in this study. Logarithmic equations which required critical temperature (Tc) and normal boiling temperature (Tb) were proposed for the fatty acids and their corresponding triglycerides. The method predicted with good accuracy the critical pressures (Pc) of the n-fatty acids, even without the input of the compressibility factor (ΔZb). The deviations of predicted critical pressures from experimental values were between (0-7)%, except for Caproic and Caprylic acids; where the method under predicted the critical pressures with deviations of -6.64% and -11.31% respectively. Experimental Pc values for the triglycerides were not available in the open literature for comparison.
Abstract: A new and useful method for evaluating and predicting the critical pressures (Pc) of n-fatty acids and triglycerides was developed in this study. Logarithmic equations which required critical temperature (Tc) and normal boiling temperature (Tb) were proposed for the fatty acids and their corresponding triglycerides. The method predicted with good a...
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Computational Investigation on Substituent and Solvent Effects on the Electronic, Geometric and Spectroscopic Properties of Azobenzene and Some Substituted Derivatives
Isaiah Ajibade Adejoro,
Oluwatoba Emmanuel Oyeneyin,
Babatunde Temitope Ogunyemi
Issue:
Volume 3, Issue 6, November 2015
Pages:
50-57
Received:
18 November 2015
Accepted:
27 November 2015
Published:
16 December 2015
Abstract: Computational investigation on the ground state properties of trans-azobenzene and four kinds of hydroxy-ended azobenzene-type chromophores containing different substituent groups as electron donor and acceptor in different solvent media was carried out. The effects ofsubstituents –I2, -OH- and -CH3, -NH2, and –Cl2 on the electronic properties like the EHOMO, ELUMO, band gap, dipole moments, global hardness, electrophilicity indices were studied using the Ab initio restricted DFT self-consistent field method with the Becke Three Lee Yang Parr (B3LYP)/6-31G* method in vacuum, water, diethylether, ethanol and acetone. The results showed that these properties were altered upon substitution with different groups. The azobenzene gave a slight difference in its band gap in different solvent changing from (3.95 eV) in vacuum to the lowest (3.87 eV) in acetone but changes drastically as we introduce different substituents. It was also found that the dipole moment (μ), polarizability (α), absorption wavelength (λab) gave slight change in different solvents but rapidly increased as the band gap reduces, invoking their reactivities. They are also red-shifted as different substituents are added. Of all the studied molecules, compound H gave the lowest band gap of 0.46 eV, the highest dipole moment (875.02 D), the highest polarizability (64.97C.m2V-1) and it is the most red-shifted (401.13 nm). Molecule H therefore, has the lowest band gap, highest polarizability and dipole moment. It also has the highest molecular size and the highest planarity. This means that the molecule is the most reactive, most polarizable, highest electro-optic response and it is the softest.
Abstract: Computational investigation on the ground state properties of trans-azobenzene and four kinds of hydroxy-ended azobenzene-type chromophores containing different substituent groups as electron donor and acceptor in different solvent media was carried out. The effects ofsubstituents –I2, -OH- and -CH3, -NH2, and –Cl2 on the electronic properties like...
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Complex Hydrides Li2MH5 (M = B, Al) for Hydrogen Storage Application: Theoretical Study of Structure, Vibrational Spectra and Thermodynamic Properties
Melkizedeck Hiiti Tsere,
Tatiana P. Pogrebnaya,
Alexander M. Pogrebnoi
Issue:
Volume 3, Issue 6, November 2015
Pages:
58-67
Received:
9 November 2015
Accepted:
26 November 2015
Published:
18 December 2015
Abstract: Gaseous lithium complex hydrides Li2MH5 (M = B, Al) have been studied using DFT/B3P86 and MP2 methods with 6-311++G(d,p) basis set. High content of hydrogen by these materials accord them with good candidacy as a class of hydrogen storage materials. The optimized geometrical parameters, vibrational spectra and thermodynamic properties of the hydrides and the subunits LiH, Li2H+, Li2H2, MH3, MH4−, and LiMH4 have been determined. For the LiBH4 the equilibrium configuration was tridentate of C3v symmetry. For LiAlH4 two isomeric forms, bidentate (C2v) and tridentate (C3v), were confirmed to exist, and C2v isomer was shown to dominate in saturated vapor. For complex hydrides Li2MH5, different structural forms were considered but only one asymmetric form (C1) appeared to be equilibrium. Several possible channels of dissociation of Li2MH5 were considered; the enthalpies and Gibbs free energies of the reactions were computed. The enthalpies of formation ∆fH(0) of the complex hydrides in gaseous phase were determined: 60 ± 10 kJmol1 (Li2BH5) and 33 ± 10 kJmol1 (Li2AlH5). Heterophase decomposition of the gaseous Li2MH5 with solid products LiH and B/Al and hydrogen gas release was shown to be spontaneous at ambient temperature. Production of hydrogen gas via gaseous decomposition is highly endothermic and achievable at elevated temperatures. The complexes Li2MH5 are therefore proposed to be useful hydrogen storage materials under appropriate conditions.
Abstract: Gaseous lithium complex hydrides Li2MH5 (M = B, Al) have been studied using DFT/B3P86 and MP2 methods with 6-311++G(d,p) basis set. High content of hydrogen by these materials accord them with good candidacy as a class of hydrogen storage materials. The optimized geometrical parameters, vibrational spectra and thermodynamic properties of the hydrid...
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