Structural Data, Linear and Nonlinear Optical Properties of Some Cyclic Phosphazenes: A Theoretical Investigation
Pages 132-142
D. Hadji and A. Rahmouni

DOI: http://dx.doi.org/10.6000/1929-5030.2015.04.03.1

Published: 08 September 2015

Abstract: We report ab initio and DFT calculation of structural data, dipole moment, diagonal vibrational and electronic contributions to polarizability, vibrational and electronic contributions to first hyperpolarizability of some cyclic phosphazenes. The electronic structure of substituted cyclic phosphazenes has been investigated using Hartree-Fock and density functional theory. The vibrational and electronic contributions to polarizabilities and first hyperpolarizability of these molecules were calculated with HF method, and different DFT levels used the traditional B3LYP and PBE functional and the long-range corrected functional like Coulomb-attenuating method CAM-B3LYP, LC-BLYP and wB97XD used different basis sets. These cyclic phosphazenes adopts a planar structure. The study reveals that the cyclic phosphazenes derivatives have large vibrational contribution to static first hyperpolarizability values. The results obtained from this work will provide into the electronic properties of this important class of inorganic polymers.

Keywords: Mean polarizability, polarizability anisotropy, vibrational and electronic polarizability, vibrational and electronic first hyperpolarizability.

Substituent Effects on the Activation Parameter Changes for the Aminolysis in the Bimolecular Nucleophilic Reactions in Solution
Pages 81-93
Vladislav M. Vlasov

DOI: http://dx.doi.org/10.6000/1929-5030.2014.03.02.6

Published: 30 May 2014

Abstract: Variation of the activation parameters for the aminolysis in the S_N2, acyl-transfer, S_NAr and Ad_N reactions offers an additive mechanistic tool for the studies of these reactions in solution. This approach uses the substituent effects on the benzene and pyridine rings to the variation of the activation parameters, ΔX^≠ (X = H, S, G), in the above reactions in the frameworks of the Hammett – like equations in order to evaluate the resultant δΔX^≠ reaction constants. The single linear dependences of the internal enthalpy constants δΔH^≠_int on the δΔG^≠ and the Hammett ρ constants show that the substituent effects in the leaving and nonleaving groups and nucleophiles on the mechanistic features in aminolysis of bimolecular nucleophilic reactions are governed by the magnitude of δΔH^≠_int when one of the steps of the process is the single rate-determining step.

Study of Molecular Interactions in Binary Mixtures of Diethyl Carbonate + Benzene Derivatives at Different Temperatures
Pages 119-127
K. Narendra,B. Sudhamsa, M. Sarath Babu and T.S. Krishna

DOI: http://dx.doi.org/10.6000/1929-5030.2015.04.02.4

Published: 16 June 2015

Abstract: Investigation on the molecular interactions between binary mixtures containing diethyl carbonate in combination with nitrobenzene, chlorobenzene and aniline is presented. Ultrasonic velocity and density values were determined for the individual components as well as binary mixtures of the above benzene derivatives with diethyl carbonate at temperatures (293.15, 298.15, 303.15, 308.15, 313.15, 318.15 and 323.15) K over the entire composition range. Further, adiabatic compressibility and acoustic impedance values were calculated using the experimental results. In addition to these parameters, the excess parameters like excess adiabatic compressibility, excess acoustic impedance and deviation in ultrasonic velocity were also obtained. Based on all these results, molecular interactions among the selected components were discussed.

Keywords: Ultrasonic velocity, density, molecular interactions, binary mixtures, diethyl carbonate.

Surfactant Assisted Synthesis of Homogeneous Calcium Based CO₂ Sorbent at Room Temperature
Pages 175-185
Chee Yew Henry Foo, Abdul Rahman Mohamed, Keat Teong Lee and Dahlan Irvan

DOI: http://dx.doi.org/10.6000/1929-5030.2014.03.03.6

Published: 18 September 2014

Abstract: Calcium oxide (CaO) sorbents have been recently used for removal of CO₂ gases in fossil fuel-fired power plant. However, there are some limitations of CaO in CO₂ capturing such as rapid loss of activity during the capture cycles, which is a result of sintering, attrition, and consequent elutriation. Therefore, this paper has demonstrated a novel synthesis method to produce CaO at room temperature to avoid abovementioned drawbacks. In addition, introduction of ionic surfactant of sodium dodecyl sulfate to the CaO formation solution has shown a positive result of formation of homogeneous spherical particle with a mean Z-average diameter of 345.2 nm and polydispersion index (PDI) of 0.335 by dynamical light scattering measurement. Subjected to a high calcination temperature of 1200^oC, developed CaO is able to maintain a CO₂ uptake capacity of 0.1025 g_CO2/g_sorbent under 30 minutes of carbonation time. Despite its lower CO₂ uptake capacity compared to maximum theoretical limit of 0.78 g_CO2/gsorbent, CaO particles is able to withstand a high calcination temperature of 1200^oC and reported a particle size distribution ranged from 0.4 - 1.2µm after calcination which is just slightly larger than fresh developed CaO. Given that such small narrow distributed size of CaO, developed CaO at room temperature is good for packed-bed reactor in calcium looping processes and more studies are required to find a suitable support for fluidized bed reactor type. This successful synthesis story of CaO particle at room temperature has unraveled the possibility to develop nanosized CaO at room temperature in order to achieve high CO₂ uptake capacity while enjoying its superior thermal stability over multiple carbonation/calcination cycles. .