Journal of Physical and Theoretical Chemistry
Volume:10 Issue: 2, Summer 2013

Separation and capture of carbon dioxide from the flue gas of power plants in order to reduceenvironmental damages has always been of interest to researchers. In this study, aqueous solution ofmethylamine was used as an absorbent for CO2 capture. In order to study this reaction, DensityFunctional Theory (DFT) was employed at the level of B3LYP/6-311++G(d,p) by using theconductor-like polarizable continuum model (CPCM). Two possible reaction products were studied:carbamate ion and bicarbonate ion. The estimation of the thermodynamic parameters indicated thatthe reaction of bicarbonate ion forming is not thermodynamically feasible at room temperature.However, the reaction of carbamate ion formation is exothermic (ΔH= -12.4 kcal mol-1) andexergonic (ΔG= -1.48 kcal mol-1). Also, various atomic radii were employed to build up the solutecavity within CPCM model and the effects of the solute cavity on the thermodynamic properties ofthe reaction were studied.

In the present work, impact of Lewis acid (LA) catalysts BF3, BCl3, and BBr3 on the kinetics andregioselectivity of 1,3-dipolar cycloaddition (1,3-DC) reaction between azidobenzene and acroleinwas theoretically studied using B3LYP/6-31G* level. Our results indicate while the uncatalyzed 1,3-DC reaction under investigation takes place via a non-polar, non-regioselective, and lowasynchronous process, the LA catalyzed 1,3-DC reaction takes place via a polar, regioselective, andhigh asynchronous process. In addition, the barrier height of the studied 1,3-DC reaction isconsiderably reduced in the presence of LA catalysts, and the catalytic activity of LAs in order toincrease the electrophilicity character of acrolein and, consequently, to reduce barrier height ofreaction, is increased with the increase of halogen atom size; BBr3> BCl3> BF3. Regioselectivity inthese LA catalyzed 1, 3-DC reactions appears to be controlled by steric repulsion effects between theLA catalyst and the azide phenyl substituent instead of the electronic effects.

In the present work, the regioselectivity for a series of Diels–Alder reactions (4 reactions) has beenstudied using hardness, electrophilicity and polarizability of products.Furthermore,thermodynamicand kinetic calculations have been done. In all results predicted pararegioisomer is more favorableregioisomerinthese investigated reactions.All calculations have been done at the DFT-B3LYP/6-31G(d) level of theory.

Using the Gaussian 2003 software and MP2/ 6–311 ++ G** method for He: He, Ne:Ne andMP2/6-31G method for Ar: Ar, Kr: Kr and HF/STO-3G method for Xe: Xe, the optimizedinteraction energies between two like atoms of rare gases (He, Ne, Ar, Kr and Xe) as a functionof the distances between the centers of two considered atoms were evaluated and the resultswere interpreted according to the Lennard – Jones equation . In addition, the second virialcoefficient of each rare gas was calculated upon the appropriate equations of statisticalthermodynamics. The resultent coefficients were comparable with those are available in theliterature.

Methyl orange is one dye resulted from the textile industry. The aim of this study is to test theadsorption capacity of nickel oxide nanoparticles for removing the methyl orange from aqueoussolution. The parameters studied were the effect of temperature, contact time and initial pH ofsolution. Results indicate that the removal efficiency of nickel oxide nanoparticles increases withincreasing concentration of methyl orange and temperature. Adsorption isotherms were investigatedto complete understanding the adsorption processes. The adsorption behavior was analyzed byLangmuir, Freundlich and Tempkin isotherms. The values of correlation coefficients (R2) showedthat the Langmuir isotherm model has a better fitting than Freundlich and Tempkin isotherms.Sorption kinetic data were fitted to the pseudo second-order model.

Hydroxyapatite nanocrystals were synthesized by sol-gel combustion method for the sorption ofHg(II) ions from aqueous solutions. The effects of varying parameters such as pH, temperature, initialmetal concentration, and contact time on the adsorption process were examined. Adsorptionequilibrium was established in 360 minutes and the maximum adsorption of Hg(II) on thehydroxyapatite was observed to occur at pH 7.0. The adsorption data correlated with Freundlich andLangmuir isotherms. The Langmuir isotherm showed a better fit to the equilibrium data. Theadsorption thermodynamic parameters (ΔG 0, Δ H 0, and Δ S 0) were calculated which showed anendothermic adsorption process. The equilibrium parameter (RL) indicated that hydroxyapatitenanocrystals are useful for Hg(II) removal from aqueous solutions.

Metal oxides play a very important role in many areas of chemistry, physics and materials science.The metal elements are able to form a large diversity of oxide compounds. In this investigation, wesynthesis SnO2 and C,N,S-tridoped SnO2 nanoparticles by precipitation method. The synthesizedSnO2 and C,N,S-tridoped SnO2 nanoparticles were characterized by instrumental analysis methods,such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electronmicroscopy (SEM) and transmission electron microscopy (TEM) techniques. The observed resultsshowed particle size 30 nm.

In this paper we studied the thermal negativity in a two-qubit XX spin ½ chain model and XXX spin1/2 chain model(isotropic Heisenberg model)spin-1/2 chain subjected to an external magnetic field inz direction. We calculate analytical relation for the thermal negativity for two qubit XX and XXX spinchain models in the external magnetic field. Effects of the magnetic field and temperature on thenegativity are shown. We have also plotted two kind of behavior in the thermal negativity whichscales by magnetic field and temperature. It is shown that when the magnetic field along in axis z isconsiderable, thermal negativity can be decrease for higher temperature. We found the criticaltemperature of negativity for XX spin chain model and XXX spin chain model with added externalmagnetic field where there are independent from magnetic field. We also have shown in both of twomodels after T=TC the negativity is zero. We find the critical temperature for this models and showthat the critical temperature is independent of magnetic field. We found that the negativity withincreasing the temperature T, at first the quantum correlations in the system increase, smoothlyreaches the maximum, and then after the critical temperature turn into zero.