A solution- and solid-phase approach to tetrahydroquinoline-derived polycyclics having a 10-membered ring

With the goal of library generation using a polycyclic derivative 5 having an enamide functional group, a simple and practical, enantioselective synthesis of tetrahydroquinoline derivative 2 was achieved. The phenolic hydroxyl group in compound 2 was utilized as an anchoring site for solid-phase synthesis. The ring closing metathesis approach yielded the desired polycyclic product 5 on solid phase in five steps (overall 40% yield). Compound 5 is a novel scaffold for the library generation of natural product-like polycyclics having a functionalized medium ring for obtaining a new class of small molecules to be utilized as chemical probes.     

Prediction of gas condensate properties by Esmaeilzadeh–Roshanfekr equation of state

The Esmaeilzadeh–Roshanfekr (ER) equation of state (EOS) is used to predict the PVT properties of gas condensate reservoir fluids. Three gas condensate fluid samples taken from three wells in a real field in Iran, referred here as SA1, SA4 and SA8, as well as five samples from literature have been used to check the validity of the ER EOS in calculating the PVT properties of gas condensate mixtures. Some experiments such as constant composition expansion (CCE), constant volume depletion (CVD) and dew point pressures are carried out on these samples. In order to have an unbiased comparison between the ER and the Peng–Robinson (PR) equation of state, van der Waals mixing rules are used without using any adjustable parameters (k_ij = 0). Also, no pure component parameters are adjusted. The critical properties and acentric factor for plus-fraction are estimated by the Kesler–Lee, Pedersen et al. and Riazi–Daubert characterization methods. The results of dew point pressure calculations show that the ER EOS has smaller error than the PR EOS. For some mixtures, relative volume, gas compressibility factor and condensate drop-out in CVD and CCE test were also predicted. Comparison results between experimental and calculated data indicate that the ER EOS has smaller error than the PR EOS. The total average absolute deviation was found to be 0.82% and 2.97% for calculating gas compressibility factor and gas specific gravity in CVD test. Also, the total average absolute deviation was found to be 2.06% and 3.42% for calculating gas compressibility factor and relative volume in CCE test.     

Synthesis of pyrazoles and oxyquinoxalines from 2,4-dioxohexenoales

Condensation of ethyl 2,4-dioxo-6-phenylhex-5-enoates (I; R = H, I; R = Me, I, R = Ph) with various hydrazines yielded ethyl 5-styrylpyrazole-3-carboxylates (III), which were hydrolyzed to the acids (IV), and ozonized to 5-keto pyrazole esters (VI) and acids (VII). Reduction of the 5-formylpyrazoles (VI; R = II) with borohydride afforded the 5-hydroxymethyl derivatives (VIII). The same 2,4-dioxohexenoates (I) when treated with o-phenylenediamine gave 2-oxy-quinoxalines (V; R = H, V; R = Me, V; R = Ph). The uv spectra data of these compounds are given.     

Determination of carbamazepine in formulation samples using dispersive liquid–liquid microextraction method followed by ion mobility spectrometry

A simple, sensitive, fast and efficient method based on dispersive liquid–liquid microextraction (DLLME) followed by ion mobility spectrometry (IMS) has been proposed for preconcentration and trace detection of carbamazepine (CBZ) in formulation samples. In this method, 1 mL of methanol (disperser solvent) containing 80 μL of chloroform (extraction solvent) was rapidly injected by a syringe into a sample. After 5 min centrifugation, the preconcentrated carbamazepine in the organic phase was determined by IMS. Development of DLLME procedure includes optimization of parameters influencing the extraction efficiencies such as kind and volume of extraction solvent, disperser solvent and salt addition, centrifugation time and pH of the sample solution. The proposed method presented good linearity in the range of 0.05–10 μg mL^?1 and the detection limit was 0.025 μg mL^?1. The repeatability of the method expressed as relative standard deviation was 6 % (n = 5). This method has been applied to the analysis of carbamazepine formulation samples with satisfactory relative recoveries ≤75 %.     

The Lichtenbaum-Hartshorne theorem for modules which are finite over a ring homomorphism

Let φ:(R,m)→S be a flat ring homomorphism such that mS≠S. Assume that M is a finitely generated S-module with dim_R(M)=d. If the set of support of M has a special property, then it is shown that if and only if for each prime ideal satisfying , we have . This gives a generalization of the Lichtenbaum-Hartshorne vanishing theorem for modules which are finite over a ring homomorphism. Furthermore, we provide two extensions of Grothendieck’s non-vanishing theorem. Applications to connectedness properties of the support are given.     

Modification of Esmaeilzadeh–Roshanfekr equation of state to improve volumetric predictions of gas condensate reservoir

The Peneloux–Rauzy–Freze (PRF) method of improving volumetric predictions by introducing the volume shift into the equation of state, is applied to the Esmaeilzadeh–Roshanfekr equation of state (ER-EOS). The ER-EOS is a new three parameter equation of state that was developed in 2006 aiming to be applied to reservoir fluids. First, this equation of state was developed for pure hydrocarbons and then was extended to mixtures by using mixing rules [M. Bonyadi, F. Esmaeilzadeh, Fluid Phase Equilib. 260 (2007) 326–334]. The modified ER-EOS (mER-EOS) is expected to improve volumetric predictions of gas condensate by applying volume shift for heavy end(s). In this study, three gas condensate fluid samples taken from three wells in a real field in Iran, referred here as SA1, SA4 and SA8, as well as two samples from literature have been used to check the validity of the modified ER-EOS in calculating the PVT properties of gas condensate mixtures. Some experiments such as constant composition expansion (CCE), constant volume depletion (CVD) and dew point pressures are carried out on these samples. Relative volume and condensate drop-out in CCE and CVD tests were predicted by ER-EOS, mER-EOS, PR-EOS and SRK-EOS [D.Y. Peng, D.B. Robinson, Ind. Eng. Chem. Fundam. 15 (1), (1976) 59–64; G. Soave, Chem. Eng. Sci. 27 (1972) 1197–1203]. Comparison results between experimental and calculated data indicate that the mER-EOS has smaller error than the ER-EOS, PR-EOS and SRK-EOS. By this modification, the total average absolute deviations of the predicted liquid saturation from CVD experiments and relative volume from CCE experiments are 13.17% and 0.99%, respectively.     

Adsorption of asphaltene from crude oil by applying polythiophene coating on Fe3O4 nanoparticles

The objective of the present study was to investigate the potential use of applying polythiophene coating on magnetic Fe₃O₄ nanoparticles for the enhancement of asphaltene adsorption. Two stages of experimental were conducted. In the first stage, the ability of coated nanoparticles for asphaltene adsorption in synthetic asphaltene-toluene solution was evaluated. The effects of parameters such as nanoparticles concentration, initial concentration of asphaltene, and temperature were studied. In the second stage, the performance of the coated nanoparticles for the adsorption of asphaltene from crude oil was investigated under atmospheric pressure and a pressure-volume-temperature (PVT) apparatus was utilized for simulated reservoir conditions. Fe₃O₄ and Fe₃O₄-PT MNPs were synthesized using an effective co-precipitation method. The results of the first-stage tests indicated that the maximum adsorption capacity values for Fe₃O₄ and Fe₃O₄-PT MNPs were 0.79 and 1.09?mg?m^?2, respectively. The optimum value of nanoparticles concentration was approximately determined as 10?g?L^?1. According to the adsorption isotherms and kinetics, the Langmuir and pseudo-second-order Lagergren models were consistent with the experimental data, respectively. The average adsorption efficiencies for Fe₃O₄-PT and Fe₃O₄ MNPs were 78.98 and 65.94%, respectively. The results of the performed experiments on crude oil showed that Fe₃O₄-PT MNPs could adsorb asphaltenes from crude oil in a similar trend as synthetic asphaltene-toluene solution.     

Synthesis of molecular imprinted polymer nanoparticles followed by application of response surface methodology for optimization of metribuzin extraction from urine samples

A molecular imprinted polymer was prepared with precipitation polymerization technique and applied as a sorbent for selective extraction and enrichment of metribuzin herbicide prior to high performance liquid chromatography. Optimization of critical variables affecting the efficiency of molecularly imprinted solid-phase extraction (MISPE), such as sorbent mass, sample pH and flow rate of sample, volume, concentration, and flow rate of elution solvent was done by employing central composite design (CCD) of the response surface methodology. Two separate models were developed for the adsorption and recycling steps. The analysis of variance (ANOVA) demonstrated that, experimental data were excellently fitted to the proposed response models. The optimum operating conditions were: a sorbent mass of 25 mg, sample pH 6.19, sample flow rate of 2.15 mL/min, and a 5 mL portion of methanol/acetic acid with 92.7:7.3 (v/v) ratio and flow rate of 2.1 mL/min for the extraction process. Under the optimized conditions, the linear range was obtained from 20 to 120 µg/L (R²?=?0.999) and the lowest detectable concentration (LOD) and the lowest quantitative concentration (LOQ) were calculated as 5.75 and 19.86 µg/L, respectively. Finally, the designed MISPE method was successfully applied to determine trace amount of metribuzin in real samples. The diluted urine samples were spiked with metribuzin at 4 levels and extracted with recoveries ranging from 93.82 to 97.84% and the relative standard deviation (RSD) less than 4.8%.     

Biosynthesis,characterization, and antibacterial activity of silver nanoparticles using Rheum turkestanicum shoots extract

Research on Chemical Intermediates - Silver nanoparticles (Ag-NPs) were synthesized through a facile and “green” method, which uses the aqueous shoots extract of Rheum turkestanicum at...