Iranian Journal of Chemistry and Chemical Engineering
Volume:34 Issue: 4, Jul-Aug 2015

Hartree-Fock (HF) and Density Functional Theory (DFT) methods employed to study the effect of conformational change on the 13C chemical shifts of 6-mono axial and equatorial substituted and 6,7-di axial-axial, equatorial-equatorial and axial-equatorial substituted derivatives of 5,6,7,8-tetrahydrodibenzo[a,c]cyclo-octene. The geometry of the conformers have been optimized in the gas phase employing the 6-311G(d,p) basis set. The 13C chemical shifts were calculated by Gauge Including Atomic Orbitals (GIAO) method. The correlation between calculated 13C chemical shifts in the gas phase and experimental ones in CDCl3 solvent is linear with squared regression coefficient of 0.96. Also the calculated 13C chemical shift in the gas phase by the HF method shows better correlation with experimental ones compared with DFT method. Calculations of both the paramagnetic and diamagnetic shielding of carbon atoms demonstrate that the difference between experimental 13C chemical shifts of the axial and equatorial substituted carbon atoms are more due to the paramagnetic than the diamagnetic shielding.

Trifluoromethylated organic compounds, especially chiral quaternary alcohols bearing trifluoromethyl group are of important intermediates in drugs, agrochemicals and etc. An efficient epoxidation of β-CF3-β,β-disubstituted unsaturated ketones (6) has been developed with environmental benign hydrogen peroxide as the oxidant and F5-substituted chiral quaternary ammonium salt (1g or 5) derived from cinchona-alkaloid as the catalyst. Using 3 mol% of the catalyst, both enantiomers of (R,R) and (S,S) β-trifluoromethyl-α,β-epoxy ketones (7, 8) were obtained in excellent diastereoselectivities (up to 100:1 d.r.) and enantioselectivities (up to 99.7% ee). The effects of catalyst structure, catalyst loading, substrate structure, the nature of oxidant, and reaction conditions on the catalyst capacities have been discussed in full length. The reaction mechanism was proposed to explain the origin of chiral induction. By subsequent reduction with zinc the epoxides are exhibited to be converted into trifluoromethylated quaternary alcohols without any loss in enantioselectivities. All new compounds are fully characterized by IR, NMR, elemental analysis and or high resolution mass spectrum.

: The surface of SBA-15 was modified by diphenylphosphine; then, it was treated with butane sultone and sulfuric acid to obtain Brønsted acid HO3S-phosphonium based ionic liquid functionalized SBA-15 with HSO4- as a counteranion. It efficiently catalyzed synthesis of pyrano[3,2-c]chromenone derivatives through the reaction of 4-hydroxycoumarin and chalcones at 60 °C in water/ethanol. Good yields, mild reaction conditions, and user-friendly procedure are advantages of this method. Also, the catalyst could be easily separated and reused five times without significant reduction of activity.

: An efficient and eco-friendly protocol for the preparation of 2-amino-4H-chromenes employing a multi-component, one-pot condensation reaction between aromatic aldehydes, malononitrile and 1-naphthol has been developed. The reaction of 1-naphthol with malononitrile and various aromatic aldehydes was carried out in water-ethanol (1:1) at reflux using 20 mol% of diammonium hydrogen phosphate as catalyst. The results show that aromatic aldehydes containing electron-donating groups or electron-withdrawing groups could react smoothly to give the corresponding products in good to excellent yields. It was also found that diammonium hydrogen phosphate can be recycled at least four times without loss of activity. The operational simplicity, easy work-up, short reaction time, together with the use of non-toxic, commercially available, inexpensive and recyclable catalyst are remarkable features of the procedure.

In this research work the solid-solutions of (Bi2O3)1-x (Co2O3)x, [x= 0.05, 0.1] (1), (Bi2O3)1-x (Ho2O3) x, [x= 0.025, 0.05] (2), and (Bi2O3)1-x-y (Co2O3)x (Ho2O3)y, [x=0.05]; [y= 0.01, 0.02] (3) have been synthesized using sol-gel method. The effects of transition metal oxides doping on the crystallization and phase transition of the Bi2O3 were discussed by X-Ray Diffraction (XRD). The XRD pattern showed that 1 and 3, have Body Center Cubic (bcc) single phase; similar to γ- Bi2O3. While 2, has phase transition from bcc to tetragonal phase. The surface morphology of the samples was assessed by Scanning Electron Microscopy (SEM). Furthermore electrochemical properties of electrodes modifying by these new synthesized ceramics were studied by Cyclic Voltammetry (CV).

The effect of acetate ion introduced to aqueous solutions was investigated for the extraction/separation of Ni and Co from a dilute sulfate media. The separation of Co and Ni was improved by introducing acetate to aqueous media. By the use of the slope analysis method, the stoichiometric coefficient of the extractant was found to be 4 for cobalt and 3.5 or 4 for nickel depending on the acetate concentration. Fourier Transform Infrared Spectroscopy (FT-IR) was utilized to examine the probable“metal-acetate-D2EHPA” complexes. Increasing the level of acetate, up to 0.4 M showed a relatively significant effect on the extraction curve of Ni, but there was no influence in the Co extraction curve. At the acetate level of 0.6 M, the pH difference at 70 extraction percentage reached 0.55 in compared to 0.2in the absence of acetate.

This article reports a study of the thermo-oxidation and biodegradation in the soil of low-density polyethylene/starch films (LDPE/starch) by infrared spectroscopy: Films of LDPE/Starch blends of different composition (starch content range from 0 to 15% w/w), were prepared and exposed to thermo-oxidation at different temperatures at 80, 90 and 100°C, and buried in the soil of public dump during 300 days. The oxidation, for films subjected to thermal oxidation, was revealed by the appearance of absorption bands of carbonyl groups centered at 1715 cm-1. After the induction period, which varies from 12 to 14 days according to the concentration of starch incorporated in the films, the indication of carbonyl croup increases with time and temperature of exposition. During the first 30 days, the rate of oxidization is the weaker, the larger percentage of starch in the film of LDPE. The biodegradation of films buried in the soil for 300 days, was followed by infrared spectroscopy. The carbonyl index calculated at 1715 cm-1 and at 1744 cm-1 showed the oxidation of films LDPE/starch. This index increases with time of burial and starch percentage incorporated into LDPE films during the first 180 days in soil burial, then decreases.

The mineral contents of Centaura leave and seeds were determined by Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES). Macro element concentrations (P, K, Ca, Mg and S) of samples were found at high levels. K was established at high level in both leave and seed samples of Centaurea. While K contents of leaves changes between 7254.10 mg/kg (Centaurea lycaonica) and 26396.36 mg/kg (Centaurea pterocaula), it ranged from 6242.22 mg/kg (Centaurea salicifolia) to 15182.07 mg/kg (Centaurea cariensis). Ca contents of leaves changed between 6268.70 mg/kg (Centaurea derderiifolia) and 23471.24 mg/kg (Centaurea stapfiana). The same element was found between 1963.45 mg/kg (Centaurea salicifolia) and 12470.46 mg/kg (Centaurea stapfiana). Fe contents of leaves changed between 55.52 mg/kg (Centaurea cariensis Boiss. subsp. longipapposa) and 502.47 mg/kg (Centaurea salicifolia). Na content ranged from 324.27 mg/kg (Centaurea cariensis) to 4938.52 mg/kg (Centaurea cariensis). Anthocyanin contents of leaves ranged from 16.3 µmol/g (Centaurea kizildaghensis) to 109.3 µmol/g (Centaurea stapfiana). While total phenolic contents of leaves change between 693.5 mg gallic acid/g extract and 826.3 mg gallic acid/g extract, total phenolic content of seeds ranged from 655.1 mg gallic acid/g extract (Centaurea derderiifolia) to 1342.0 mg gallic acid/g extract (Centaurea cariensis Boiss. subsp. longipapposa). Total flavonoid contents of Centaurea leaves changed between 49.2 mg catechol/g (Centaurea nigrofimbria) to 157.5 mg catechol/g (Centaurea pterocaula).

Carbon paste electrode was modified by disodium 2,4-diamino-7-methylbenzo[g] pteridine-5,10-dioxide to fabricate a sensor for potentiometric determination of vanadyl ion (VO2+) in aqueous medium. The new ligand was synthesized in three steps with high yield. The optimal composition of the carbon paste was made of graphite powder (64.5%), ionophore (16.6%), paraffin oil (17.8%), and sodium tetraphenylborate (NaTPB, 1.1%). The electrode exhibited a constant sensitivity of 30.20 ± 0.5 mV to VO2+ ions over a concentration range of 5 M to 1 mM. The detection limit was calculated to be 5 with a response time of less than 35 s. The electrode showed to be highly reproducible over a period of 3 weeks. This sensor exhibits high selectivity to VO2+ ions and was successfully employed for potentiometric titration of VO2+ ions with EDTA.

In this paper, vapor pressure for pure compounds is estimated using the Artificial Neural Networks and a simple Group Contribution Method (ANN–GCM). For model comprehensiveness, materials were chosen from various families. Most of materials are from 12 families. Vapor pressure data of 100 compounds is used to train, validate and test the ANN-GCM model. Vapor pressure data were taken from literature for wide ranges of temperature (68.55-559.15 K). Based on results, the best structure for feed-forward back propagation neural network is Levenberg-Marquardt back propagation training algorithm, logsig transfer function for hidden layer and linear transfer function for output layer. The multiplayer network model consists of temperature, acentric factor, critical temperature, critical pressure and the structure of molecules as inputs, 10 neurons in the hidden layer and one neuron in the output layer corresponding to vapor pressure. The weights are optimized to minimize error between experimental and calculated data. Results show that optimum neural network architecture is able to predict vapor pressure data with an acceptable level. The trained network predicts the vapor pressure data with average relative deviation percent of 1.18%.

This paper presents a numerical study of local mass transfer coefficients in a 90° bend using the RNG version of k– model to include the influence of curvature on the turbulent transport. Simulations were performed for flow through a 90°, 3-D bend for Reynolds numbers of 13500, 90000, and 390000, Schmidt numbers of 2.53 and 700 and curvature ratios of 1.5, 2, and 2.5. The differences between the maximum axial velocity to average velocity (Umax/Uave) predicted by the model and the experimental results reported in the literature was generally less than two percent. Simulation results showed that the ratio of the maximum Sherwood number obtained in the elbow to that obtained in fully developed pipe flow (Sh/Shp) decreased by Reynolds number (Re), Schmidt number (Sc) and curvature ratio (r/D). Maximum local mass transfer coefficient was observed at a distance of about one diameter downstream of the 90° elbow. Numerical predictions were in good agreement with experimental results reported in the literature.

Computational Fluid Dynamics (CFD) simulations of gas-solid flow through a positive low-pressure pneumatic conveyor were performed using Eulerian-Eulerian framework. Pressure drop in pneumatic conveying pipelines, creation and destruction of plugs along the horizontal and vertical pipes, effect of 90° elbows and U-bends on cross-section concentrations, and rope formation and dispersion were numerically investigated for the wheat particles at ten different operating conditions. The effects of air inlet velocity and the conveying capacity on the flow behavior were also discussed. Both parameters played a significant role in the conveying flow pattern and also the pressure drop. The numerical simulations validated against the experimental data from literature and also qualitatively compared with trends in experimental data. Excellent quantitative agreement between experimental and simulated results (±1%) was observed in dense-phase conveying. For the dilute-phase conveying simulations underestimated the values of pressure drop by 20%; however, this still falls within the acceptable error ranges reported in the literature. This study stresses the capability of CFD to explain and predict the behavior of complex gas-solid conveying systems and to be used productively for investigations in pneumatic conveying of agricultural and pharmaceutical particles as an aid in the system design..