Iranian Journal of Chemistry and Chemical Engineering
Volume:35 Issue: 1, Jan-Feb 2016

We performed molecular dynamics simulations using the coarse-grained model to study the freezing behavior of pure water and 14% water-salt mixture in a wide range of temperatures for a very long time around 50 nanoseconds. For the salty water, an interface in nanoscale was used. For both systems, the freezing behavior of water molecules was studied using some qualities such as density, total energy, and radial distribution function. For the 14% water-salt mixture, the equilibrium freezing temperature depression observed in the simulations was well consistent with the experimental data. Contrary to the water-salt mixture, however, the above-mentioned quantities changed dramatically for the pure water at the freezing point. The plots of the total energy versus time shows the freezing point of 14% water-salt mixture was 265 K that is 9 K less than the freezing point of pure water. The reduction of freezing point is in very good agreement with the experimental freezing point. The results of the simulation showed that in the less temperature than obtained freezing point, the sodium and chloride ions tendency to network formation and rejection of solution lead to reduction of water molecules accumulation.

Ab initio calculations were employed to investigate nitrogen inversion as a configuration change that can supply an infinitely useful switchable control mechanism for some complex systems. In this paper, design of a new artificial molecular nanohinge is discussed based on nitrogen inversion in which reciprocating motion of substituent in effect of inversion phenomenon, led to an open–close motion in the molecule. Since the simple secondary amines easily face inversion process in the room temperature, a carboxamide derivative was selected as the initial driver for the molecular motion. The most critical finding from this study was that, following the displacement of the substituent attached to the amide nitrogen,making the xanthenes planar be dislocated and form hinge like reversible move.

One-pot multicomponent reaction between isatin, barbituric acid, and 6-amino-1,3-dimethyl uracil was investigated in the presence of sulfonic acid functionalized nanoporous silica (SBA-Pr-SO3H) and resulted in the formation of spirooxindole dipyrimidines. Spirooxindole unit is found in many natural products and biologically active molecules and 1,4-dihydropyridines are an important class of compounds with interesting biological activities such as vasolidator, antitumor, antidiabetic, bronchodilator and anti-atherosclerotic activities. Excellent yields and short reaction timesare related to the highefficiency of SBA-Pr-SO3H that the reactions take place easily in its nano-pores. Mild reaction conditions and easy work-up procedures are other advantages of this green method.

This study represents a highly efficient and regioselective ring-opening of epoxides with acetic anhydride in the presence of NaOAc·3H2O at solvent-free conditions. The ring-opening of different classes of epoxides were carried in oil bath (70-80 °C) to afford 1,2-diacetates in high to excellent yields

A simple and efficient one-pot route for the synthesis of novel spiro [indolin– oxadiazol] derivativesby 1,3-dipolar cycloaddition reaction of nitrile oxides and isatin imine under classical or microwave irradiation conditions is described.4-amino-5-methyl-2,4-dihydro-3H-1,2,4-triazole-3-thione was synthesized by cyclization of thiocarbohydrazide and acetic acid. 3-((3-methyl-5-thioxo-1,5-dihydro-4H-1,2,4-triazol-4-yl)imino)indolin-2-one was prepared by condensation of primary amine of 4-amino-5-methyl-2,4-dihydro-3H-1,2,4-triazole-3-thione with isatin through a single step and 4'-(3-methyl-5-thioxo-1H-1,2,4-triazol-4(5H)-yl)- 3'-(substituted phenyl)-4'-hydro spiro[indolin-3,5'[1,2,4]oxadiazol]-2-one were afforded by the reaction of corresponding Schiff base with hydroximinoyl chloride and their derivatives under basic conditions at room temperature. The products were obtained in good yields. Elemental analysis, IR, 1H NMR, 13C NMR, and Mass spectral data confirmed the structure of newly synthesized compounds.

3,5-disubstituted-2,6-dicyanoaniline derivatives have been synthesized via the reaction of aryl methylene- and 1-arylethylidenemalonodinitriles using 1,8-diazabicyclo[5.4.0] undec-7-ene (DBU) as a novel and highly efficient catalyst under conventional as well as microwave conditions. Use of non-hazardous, inexpensive and readily available base catalyst, convenient procedure, short reaction time and improved product yields are some added advantages of the present protocol.

We wish to report a mild and efficient one-pot three-component reaction of an aryl aldehyde, malononitrile and barbituric acid or 4-hydroxycoumarinfor the synthesis ofpyrano[2,3-d]pyrimidine and dihydropyrano[c]chromene derivatives in the presence of iron ore pellet as a natural and reusable catalyst under heterogeneous and green conditions. The present methodology offers several advantages such as excellent yields, simple procedure and work up steps, short reaction times and easy recovery of the catalyst. We have also demonstrated that the catalyst can be reused successfully after six times using the same catalyst with high yields. Use of water as the reaction medium makes the process environmentally benign.

In this study, copper chromite (CuCr2O4) nanoparticles was prepared by inverse co-precipitation method. In this method, cupric nitrate trihydrate, (Cu (NO3)2.3H2O) and chromium nitrate nonahydrate, (Cr (NO3) 3.9H2O) with a mole ratio of 1:2 were used. Characterization of CuCr2O4 nanoparticles was performed by Fourier Transform Infrared Spectroscopy (FT-IR), Raman Spectroscopy, X-ray Diffraction Spectroscopy (XRD), Thermo-Gravimetric/Differential Scanning Calorimetry (TG-DSC), and Field Emission Scanning Electron Microscopy (FE-SEM). The results show that CuCr2O4 crystal can be obtained at temperature 520 °C. Also, phase structure of the CuCr2O4 depends on both Cu:Cr molar ratio and temperature in the starting reactants. Based on this method and under optimum conditions, the temperature for calcination (520 oC), the crystallite size of nanoparticles (18 nm), the spherical structure particles (30 to 70 nm) were obtained.

Self-assembly of densely packed ZnO nanorods were grown on Porous Silicon (PS) substrate by low-temperature chemical bath deposition. The structural and optical properties of the obtained ZnO nanostructures on PS substrate were systematically studied. The strong and sharp (002) peak compared with other peaks in the X-Ray Diffraction (XRD) indicated thatZnO nanorods formed with superior orientation toward the (002) plan.In addition, the small crystallite size and low compressive strain revealed that the self-assembly of densely packed ZnO nanorods had good crystallinity. Field-Emission Scanning Electron Microscopy (FESEM) indicated that the self-assembly of densely packed ZnO nanorods occurred on the surface, inside the pores and on the pore walls of the PS substrate. FESEM images indicated that the average diameter and length of the ZnO nanorods were 150 and 500 nm, respectively. Photoluminescence spectra (PL) exhibited a strong, sharp UV emission peak at 369 nm.

In the present investigation, a novel adsorbent, ionic liquid modified magnetic nanoparticles (IL-Fe3O4), was successfully synthesized and characterized by FT-IR spectroscopy, ThermoGravimetric Analysis (TGA), XRD analysis, Scanning Electron Microscopy (SEM) and theory of Brunauer, Emmett, and Teller (BET) for removal of Reactive Orange 122 (RO-122) from aqueous solutions. The effects of various experimental parameters such as pH, contact time, nanoparticle dosage and ionic liquid amount were studied and optimized. Experimental results indicated that the IL-Fe3O4 nanoparticles had removed more than 98% of proposed dye under the optimum conditions. Detection and quantification limits of the proposed method were 14 and 46µg/L, respectively. Desorption process of the adsorbed dye was also investigated using methanol, ethanol and propanol as the solvent. Both the adsorption and desorption of dye were quite fast. The adsorption process preferably followed the Freundlich isotherm and pseudo-second-order kinetic model. The RO-122 was removed successfully from environmental water samples too.

Adsorption of cations Al, Zn, Fe, Cr and Pb from aqueous solution of hydrogen peroxide using IR-120 cation-exchange resin was studied. The removal percentage of the cations was examined by varying experimental conditions (such as pH of the hydrogen peroxide solution, temperature, contact time and dosage of adsorbent) in a stirred-batch system. Under the optimal conditions (pH=1, T=25oC, contact time=150 min, adsorbent dosage=5g), it was found that more than 98% removal was achieved. The cations adsorption was studied on the basis of Langmuir, Freundlich and linear isotherms in the concentration range of 0-50 mg/L. Adsorption of the cations on the resin followed first-order, pseudo-first-order (Lagergren) and intraparticle diffusion kinetic models in the cations range of 10-20 mg/L. The best fitted model for kinetic model was obtained as Lagergren model. The obtained studies showed that IR-120 cation-exchange resin was successfully used as an efficient adsorbent for removal of the cations from aqueous solution of hydrogen peroxide.

α, ω-alkane-bis(N-myristoyloxyethyl-N, N-dimethyl)-diammonium bromide were synthesized and confirmed by FT-IR, FT-Raman and 1H-NMR spectroscopy. Surface tensions were measured by sigma 70 and conductivity meter EC-470C. Critical micelle concentration values were 2.70×10-4∼3.05×10-4 mol/L. The Krafft points were measured at 39.1 ~ 43.2℃. Their inhibition effects on the corrosion of low carbon steel were tested by the weight loss method in hydrochloric acid. The corrosion inhibition capacity of synthesized cationic gemini surfactant was 24.8% at 1 X 10-7mol/L concentration. Corrosion inhibition efficiency has increased by 93.8% after the concentration was increased to 1 X 10-4mol/L. As a result, these surfactants are expected to be applied as corrosion inhibitors.

A brass Vortex Tube (VT) with interchangeable parts is used to determine the optimum cold end orifice diameter, main tube length and diameter. Experiments were carried out to study the effects of operating pressure as well. It is shown that there is an optimum value for cold end orifice diameter, which is equal to 4mm and there is an optimum value for cold and hot exit temperature difference at CF=0.4.A 2-D Computational Fluid Dynamics (CFD) model is validated against the present experimental data. CFD code is applied to investigate the role of vortex tube diameter and length on the temperature separation. The code is also used to investigate and analyze the highly rotating flow field structure and its characteristic with respect to various cold fractions. Finally the results are extrapolated for investigating the effect of inlet pressures up to 1053kPa, VT on separation performances.

A numerical model for simulating Residence Time Distribution (RTD) of turbulent flows in helical static mixers is proposed and developed to improve the understanding of static mixers. The results of this model is presented in terms of different volumetric flow rate to illustrate the complicated flow patterns that drive the mixing process in helical static mixers. The computed results are also used to predict the amount of mixing that occurs within a mixing device. Such theoretical estimates need, however, always to be thoroughly checked against observations in static mixer. To check the reliability of the theoretically estimated RTD from the simulation by the application of the model equation, a comparison of the same with those obtained from observed data experiments in static mixer using statistical characteristics is done. Comparison between RTD curves shows that motionless mixture can improve the performance of reactor.