வேதியியல் அறிவியல் இதழ்

Alkylation of benzene over new modified ZSM-5 catalysts with Nd has been done in a metallic tubular reactor. The catalyst was synthesized from components modified with NdCl3 characterized by XR-Fluorescence Spectrometer, XRD apparatus, nitrogen adsorption analyzer and TGA for its acidity. The alkylation experiments have been done at different reaction temperatures, pressures and benzene (ethylbenzene)/bioethanol molar ratio in order to establish their influence on the final composition of the reaction product, selectivity and conversion. The results obtained with Nd modified catalyst were compared with those obtained from unmodified catalyst.

In this work, the fully deacetylated chitosan (FCS) was obtained from the deacetylation process of chitosan ( = 31%) in 5% NaOH solution. The structure of FCS was characterized by nuclear magnetic resonance (NMR) spectroscopy, X-Ray diffraction and Bruauer – Emment – Teller (BET) analysis. The FCS was used to adsorb Hg(II) ion from aqueous solutions. The influences of various operating parameters such as pH, temperature, initial concentration of Hg(II) ion and contact time on the adsorption capacity of FCS have been investigated. The results showed that the adsorption capacity of FCS for Hg(II) ion rapidly reached equilibrium within 60 min and strongly depended on pH and temperature. Langmuir and Freundlich adsorption models were applied to describe the isotherms and isotherm constants. It was shown that the FCS had given good correlation with Langmuir isotherm model and the adsorption kinetics of Hg(II) ion could be best described by the pseudo-second-order model.

In this work, a new polystyrene-bound single-onium phase-transfer catalyst was synthesized, and their catalytic activities were investigated in the synthesis of diethyl-2,2’-thio diacetate derivatives of thioether. The new insoluble polymer anchored mono-site phase-transfer catalyst showed significant high catalytic activity as compared to soluble single site phase-transfer catalysts. The comparative kinetic investigation reveals that the diethyl-2,2’-thio diacetate of ethyl-2-bromoacetate is faster than sodium sulfide in the presence of the new catalyst. This catalyst can be used several times with consistent catalytic activity. Experimental observations support an interfacial-type mechanism.

Gas geochemistry, an integral part of petroleum geosciences, has been used for evaluating source rocks potential for shale gas and in conventional exploration as a guide for determining potential productive formations. However, in contemporary times, new concepts of gas geochemistry have been applied in delineating the effectiveness of caprocks. Caprock is a vital element of a petroleum system, the volumes of rocks overlaying reservoirs are responsible for the configuration on which the accumulation sits and fosters essential preservation. In this study headspace gas served the purpose of delineating leakage and determining migration pathways, mechanism and discriminating gas types in the formations overlaying the reservoirs.

A novel series of 3-chloro-N-(4-oxo-2-arylquinazolin-3(4H)-yl)-1-benzothiophene-2-carboxamide analogs derived from 3-amino-2-arylquinazolin-4(3H)-one have been synthesized in good yields and characterized by IR, 1HNMR, mass spectral and elemental analyses. All the compounds were evaluated for their in vitro antibacterial activity against Gram-positive and Gram-negative bacteria and were also screened for antitubercular activity against Mycobacterium tuberculosis H37Rv strain by microplate alamar blue method. The compounds 3b and 3h showed good antitubercular and the compound 3a exhibited good antibacterial activity.

Heterocyclic compounds are acquiring more importance in recent years because of their pharmacological activities. The imidazole nucleus is an important synthetic strategy in drug discovery. Imidazole is a planar fivemember ring system with N atom in 1 and 3 positions. The systemic name for the compound is 1, 3 diazole, one of the N bear an H atom and other to be regarded as a pyrrole type N. Imidazole was first named as glyoxaline. It is amphoteric in nature, susceptible to electrophilic and nucleophilic attack. It also occurs in the purine nucleus & amino acid histidine, 4-amino-imidazole-5-carboxamide occurs naturally as a riboside. This interesting group of heterocyclic compound has diverse biological activities such as antimicrobial, anticancer, analgesic, anti-inflammatory, antiviral, anthelmintic, anticonvulsant, antiulcer, anti-allergic activity etc. Numerous methods for the synthesis of imidazoles and also their various structure reactions offer enormous scope in the field of medicinal chemistry. This articles aims to review the work reported, their chemistry and pharmacological activities of imidazole during past years.

Previous researches show that all members of chalcogene family could be a terminal in the molybdo-enzymes. But their structure as well as catalytic mechanism has not been studied much. In this paper, Density functional calculations have been performed on a model for the reductive half-reaction of the molybdo- enzymes containing Oxo, sulfido, sellenido and tellurido terminals, enabling a discussion of structural details of the Mo coordination sphere involved in the reaction with acetaldehyde.The reductive half reaction active sites, with oxo, sufido, sellenido and tellerido terminal truncated structures, were modeled using GaussView software. Energy, Mullikens charge, single negative frequency and bond descriptions of the complexes were among the very important tools obtained from the transition state structures, to study the properties of the active sites. In this work it has been found that the normalized energies for complexes with oxo, sulfido, sellenido and tellerido terminals were 433.923, 421.742, 419.284 and 403.0578 kcal/mol respectively. The decreasing trend found was the same, though the magnitudes of the energies differ significantly. The complex with oxo terminal shows considerably maximum energy barrier of 433.923 kcal in addition to its highest frequency. These are the evidence for its poor catalytic activity towards hydroxylation reaction. As a result of this and additional evidences from mulliken charge and bond length values, the reactivity of the active site towards acetaldehyde for its oxidation increases from active site with oxo to tellurido terminal. Besides, these findings give a clue for the possible natural existence of a molybdo-enzyme with Te-terminal.

We report on a new amperometric assay for Al(III) ions based on the inhibition of α-chymotrypsin enzyme. The immobilization of the enzyme was performed on screen-printed carbon electrodes modified with gold nanoparticles and polyvinyl alcohol. N-acetyl-tyrosine ethyl ester, used as enzyme substrate, produces an oxidation amperometric signal, which at increasing aluminum concentration is diminished. The developed system has a detection limit of 1.5 ± 0.1 μM (n=7) for Al(III). The reproducibility of the method is 6.6% (n=5) and its repeatability is 8.2% (n=3). Main interferences at low concentration, include As(V), Cd(II), and Mo(VI) ions. The developed method was successfully applied to the determination of Al(III) in spiked white wine sample. Results agree with the certified value giving a value of percent recovery of 103 ± 4% (n=4).