Classical chemical sciences
The objectives of the reviews are the collection, concise description, comparison and evaluation of the various chromatographic technologies using natural and modified cyclodextrins for the increase the seperation capacity of various chromatographic separation systems.
Keywords: cyclodextrins, high performance liquid chromatography, size exclusion chromatography, ultra performance chromatography, gel permeation chromatography
An efficient Hantzsch four-component condensation reaction for the synthesis of polyhydroquinolines was found to proceed in the presence of L-proline in ethanol at room temperature. The method is really simple and environmentally benign. The keys features of this protocol are the use of a bio, organic and reusable catalyst, high yields of products, using nontoxic solvent and short reaction times from the principles of green chemistry point of view.
Keywords: Synthesis; Polyhydroquinoline; L-proline; Catalyst; Four components
Reaction of copper perchlorate with sodium nitrite and pyrazine in methanol gives rise to the compound [Cu2(pyrazine)3(CH3O)2](ClO4)2 (1). This complex has been characterized through IR, combustion analysis, single crystal X-ray diffraction, and temperature dependent magnetic susceptibility measurements. Compound 1 crystallizes in the triclinic space group P-1 with the copper coordination geometry being nearly square pyramidal. The Cu(II) ions are bridged by the methoxide ions to form a dimeric structure. Compound 1 exhibits an extended 3-D network with pyrazine rings forming sheets of the copper dimers, and bridging those sheets to form a distorted honeycomb. Magnetic susceptibility measurements show a strong antiferromagnetic exchange within the methoxy-bridged copper dimers with 2J ~ –880 K
Keywords: Pyrazine, Copper(II), Synthesis, X-ray Structure, Magnetism
In the present study, a naturally occurring clay mineral, Montmorillonite, (Mt) has been explored as a carrier for an antihypertensive drug, atenolol. The effect of pH, time and initial drug concentration on drug loading capacity of Mt has been evaluated. The adsorption isotherm was fitted by the Langmuir model and follows the pseudo-second-order kinetics. The synthesized Mt-atenolol complexes were characterized by XRD, FTIR, TGA, DSC etc. XRD data indicates the intercalation of atenolol within the Mt layers. The release profile of the atenolol from Mt-atenolol complexes is compared with the pure atenolol, in simulated gastric and intestinal fluids. The release behaviour of atenolol from Mt-atenolol complexes appears to be in sustained manner over a period of 24 hours and reaches upto 40% and 27% in simulated gastric and intestinal fluids respectively. As compared to pure atenolol, extended gastric retention time was observed for Mt-atenolol complexes indicative of the increased extent of absorption and bioavailability of the drug. Various kinetic models were used to elucidate the drug release mechanism, the best fitting was found for Higuchi and Korsmeyer-Peppas model. The synthesized Mt-atenolol complexes have the potential for developing in to a sustained release formulation for oral drug delivery. Thus, proposing a promising formulation for oral sustained drug delivery of atenolol.
Keywords: Atenolol, Montmorillonite, Adsorption isotherm, Sustained delivery
The oxidation of six aliphatic aldehydes by quinolinium chlorochromate (QCC) in dimethyl sulfoxide (DMSO) leads to the formation of corresponding carboxylic acids. The reaction is first order in QCC. A Michaelis-Menten type of kinetics is observed with respect to the aldehydes. The reaction is catalysed by hydrogen ions, the hydrogen-ion dependence has the form: kobs=a + b[H+]. The oxidation of deuteriated acetaldehyde, MeCDO, exhibited a substantial primary kinetic isotope effect (kH/kD=5.78 at 298 K). The oxidation of acetaldehyde has been studied in nineteen different organic solvents. The solvent effect has been analysed using Taft's and Swain's multiparametric equations. The rate constants correlate well with Taft’s * values; reaction constants being negative. A mechanism involving transfer of hydride ion has been suggested.
Keywords: aliphatic aldehydes, correlation analysis, quinolinium chlorochromate, kinetics, mechanism, oxidation
Experimental data have been collected from the published literature for the gas-to-ionic liquid partition coefficients and molar enthalpies of solvation for over 60 solutes in the ionic liquids 1-hexyl-3-methylimidazolium tetracyanoborate ([MHIm]+[B(CN)4]–), 1-(2-methoxyethyl)- 1-methylpiperidinium bis(trifluoromethylsulfonyl)imide ([MeoeMPip]+[Tf2N]–), and 1-(2-methoxyethyl)-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([MeoeMPyrr]+[Tf2N]–) over the temperature range 318.15 K to 368.15 K. The logarithm of the gas-toionic liquid partition coefficient, logKL, have been correlated to a temperature independent free energy relationship utilizing known Abraham solvation parameters. The resulting mathematical expressions describe the experimental logKL values to within a standard deviation of 0.077 log units or less and Hsolv to within a standard deviation of 1.344 kJ mol-1 or less.
Keywords: partition coefficient, 1-hexyl-3-methylimidazolium tetracyanoborate, 1-(2-methoxyethyl)-1-methylpiperidinium bis(trifluoromethylsulfonyl) imide and 1-(2-methoxyethyl)-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, ionic liquids, temperature independence, linear free energy relationships, enthalpies of solvation.
Z-4-(Naphth-2-ylmethylene)-2-phenyloxazol-5(4H)-one and 3-(phenylcarbamoyl)but-3-enoic acid 2 and 5, respectively, are readily transformed into the corresponding perchlorate salts 3 and 6 with acetic anhydride-perchloric acid mixture. Conduct the latter salts with arenes in the presence of anhydrous AlCl3 provided novel derivatives of benzo[g]indenones 7 and 1-tetralones 8, respectively, via two consecutive Friedel-Crafts reaction in situ. The structure of all the synthesized products was characterized using IR, 1H NMR, 13C NMR and mass spectra.
Keywords: Oxazolonium perchlorates, Indanones, Domino Friedel-Crafts
Interactions of cationic tetrakis (N, N´, N´´, N´´´- tetramethyltetra-3, 4-pyridinoporphyrazinatozinc (II) [Zn (tmtppa)] with various anionic micelles of surfactants n- alkyl sulfonate and sulfate (n=11, 12, 14) have been investigated spectrophotometrically at 25 ◦C in premicellar and postmicellar region. The results have shown that with increasing the alkyl chain length of surfactants, the maximum absorbance of Zn (tmtppa) shifted to a higher wavelength and binding affinity of Zn (tmtppa) to anionic micelles increases. This confirms that the surfactant micelle, which has a longer alkyl hydrocarbon chain, enables greater solubilization of porphyrazine. Thus, the hydrophobic interaction of the porphyrazine with micelles increases in the order: C11H23SO3Na < C12H25SO4Na < C14H29SO3Na..
Keywords: Water-soluble porphyrazine; Surfactant; Premicellar aggregate; Micellized monomer, Anionic surfactant; hydrophobic interaction
The electrochemical behavior of dibenzoyl ferrocene was investigated by cyclic voltammetry in the temperature range 303–333K in the DMSO, DMF and DMA. The experimental results indicated that the redox reaction was quasi-reversible. Mass transport towards the electrode is a simple diffusion process and the diffusion coefficient (D) for redox couple has been also calculated for all the solvents. The diffusion coefficient is sensitive to the viscosity, dipolarizability and temperature of the system. These results indicated that the k0 and D increase in the following order of solvent DMSO< DMA < DMF.
Keywords: Dibenzoyl ferrocene, Cyclic voltammetry, Mass transport
The oxidation of glycolic (GA), lactic (LA), malic (ML) and a few substituted mandelic acids (MLA) by quinolinium chlorochromate (QCC) in dimethylsulphoxide (DMSO) leads to the formation of corresponding oxoacids. The reaction is first order each in QCC. Michaelis-Menten type of kinetics is observed with respect to the hydroxy acids. Reaction is failed to induce the polymerisation of acrylonitrile. The oxidation of -deuteriomandelic acid (DMA) shows the presence of a primary kinetic isotope effect (kH/kD = 5.75 at 298 K). The reaction does not exhibit the solvent isotope effect The reaction is catalysed by the hydrogen ions. The hydrogen ion dependence has the form: kobs = a + b[H+]. Oxidation of p-methyl mandelic acid has been studied in 19 different organic solvents. The solvent effect has been analysed by using Kamlet’s and Swain’s multiparametric equations. A mechanism involving a hydride ion transfer via a chromate ester is proposed.
Keywords: Correlation analysis; halochromates; -hydroxy acids; kinetics; mechanism; oxidation; quinolinium chlorochromate
A green, environmentally benign, facile and efficient one-pot three-component reaction of benzaldehyde, barbituric acid and meldrum's acid for the synthesis of 5-phenyl-5,6-dihydro-1H-pyrano[2,3-d]pyrimidine-2,4,7(3H)-trione derivatives using cerric ammonium nitrate (CAN) as a catalyst in aqueous medium under ultrasonic irradiation is described. 1,3-dimethyl barbituric acid gives slightly lower yield as compared to barbituric acid and takes longer time to complete the reaction. Excellent yields, no need of base, and simple workup procedure are the prominent features of this protocol.
Keywords: Pyrano[2,3-d]pyrimidine, 1,3-dimethyl barbituric acid, ceric ammonium nitrate (CAN), ultrasound irradiation
In this research, synthesis of (1E)-N'-((Z)-2-amino-1,2-dicyanovinyl)-N-(4-ethoxyphenyl)formamidine from imidate was investigated in the presence of different catalysts such as sulfonic acid (-SO3H), P-Toluene sulfonic acid (PTSA), aluminium chloride (AlCl3), ceric ammonium nitrate (CAN), anilinium chloride (C6H5NH3 +Cl-), Montmorillonite (K10), silica sulfuric acid (SiO2-OSO3H), silica-supported perchloric acid (HClO4-SiO2). Silica sulfuric acid exhibited high catalytic activity for this reaction and afforded excellent yields within a lesser time. Other formamidine derivatives were prepared from the reaction of imidate with amines in the presence of silica sulfuric acid under argon at room temperature.
Keywords: formamidine, imidate, sulfonic acid, aluminium chloride, anilinium chloride, silica sulfuric acid
Aldehydes have been used in a one-pot reaction with enolizable ketones, acetonitrile, benzonitrile and acetyl chloride in the presence of FePO4 at room temperature to form the corresponding β-acetamido ketones in very good yields. Three new compounds and rare β-amido ketones are reported additionally. The use of readily available FePO4 as a catalyst renders this process quite simple and convenient.
Keywords: iron(III) phosphate (FePO4); β-acetamido carbonyl compounds; catalyst; synthesis
An effective methods has been developed for the preparation under mild conditions of novel pyridazine derivatives from the easily accessible starting materials benzilmonohydrazone, p,p'-dichlorobenzilmono-hydrazone, diethyl malonate and ethyl phenylacetate. All the synthesized compounds were fully characterized and some of them displayed good insecticide activities against Mucsa domestical and Macrosiphum pisi in preliminary insecticide activity tests.
Keywords: Pyridazine derivatives, synthesis, insecticide activity, Mucsa domestica, Macrosiphum pisi
Materials and environmental chemistry
Adsorption of Pb(II) from the aqueous solutions was studied using activated carbon prepared by agricultural waste maize leaves. The influence of Pb(II) concentration (5-30 mg L-1), pH (2-8) and contact time (0-120 min.) on adsorption have been reported. Adsorption of Pb(II) is pH dependent and the results indicate that, optimum pH for the removal was found to be 4 for maize leaves activated carbon (MLAC). The Freundlich and Langmuir isotherm models were also used to describe the adsorption of Pb(II) on MLAC. Results shows that both the isotherms were fitted well. Maximum adsorption of lead on MLAC attained was 96 %. The results suggest that MLAC can be used as adsorbent for the removal of Pb(II) from aqueous solutions as industrial wastewater.
Keywords: Pb(II); Agricultural waste; Maize leaves; Activated carbon; Adsorption Isotherms; Wastewater
1-(8-Hydroxyquinolin-2yl-methyl)thiourea (HTF) has been used as a corrosion inhibitor in controlling corrosion of mild steel immersed in aqueous solution containing 60 ppm of Cl-. Weight loss method reveals that 250 ppm of HTF + 25 ppm of Zn2+ provide 95% of inhibition efficiency. Polarization study indicates that the system controls anodic reaction predominantly. AC impedance spectra reveal that a protective film is formed on the metal surface. The protective film has been analyzed using Fourier Transform Infrared and fluorescence spectra.
Keywords: Corrosion Inhibition, mild steel, fluorescence spectra, organic inhibitors, surface analysis; 1-(8-hydroxyquinolin-2-ylmethyl)thiourea
The adsorption of Malachite Green (MG) cationic dye on Al-Hussainiyat clay was first studied in a batch system for various dye concentrations. The adsorption was studied as a function of contact time, adsorbent dose, pH, and temperature under batch adsorption technique. The concentration of the solution before and after adsorption was measured spectrophotometrically .The equilibrium data fit with Langmuir and Freundlich models of adsorption and the linear regression coefficient R2 was used to elucidate the best fitting isotherm model. Different thermodynamic parameters such as Gibb’s free energy, enthalpy and entropy of the on-going adsorption process have also been evaluated. The thermodynamic analyses of the dye adsorption on Al-Hussainiyat clay indicated that the system was endothermic in nature.
Keywords: adsorption, malachite green, Langmuir model, Freundlich model, thermodynamic, clay adsorbent
Advanced wastewater treatment techniques such as adsorption are economiycally and environmentally essential in the removal of non biodegradable heavy metals from wastewater. Adsorption by activated carbon is being widely used but activated carbon remain an expensive material. In recent years, the need for safe and economical methods for the elimination of heavy metals from contaminated waters has necessitated research interest towards the production of low cost alternatives to commercially available activated carbon. Therefore there is an urgent need that all possible sources of agro-based inexpensive adsorbents should be explored and their feasibility for the removal of heavy metals should be studied in detail. This review focuses on the use of low cost adsorbent prepared from rice husk, cajanus cajan, maize cob, sago waste, mosambi fruit peel, watermelon shells, almond shells, apricot shells etc.
Keywords: wastewater treatment, low cost adsorbent, non biodegradable heavy metals
The corrosion resistance of commercial aluminium (95% pure) in simulated concrete pore solution (SCPS) prepared in natural sea water has been evaluated in the absenceand presence of curcumin extract and Zn2+.It is observed that Aluminium is more corrosion resistance in SCPS than in sea water. When curcumin extract is added to SCPS, the corrosion resistance of Al increases. However, in the presence of curcumin –Zn2+ system, the corrosion resistance of Al in SCPS decreases.
Keywords: concrete corrosion, aluminium, simulated concrete pore solution, curcumin, green inhibitor
Biochemistry, molecular biology and biotechnology
The burden of organochlorine pesticides was determined in the roots of Cryptolepis sanguinolenta, an anti malarial plant. In all fourteen organochlorine pesticides, β-HCH, δ-HCH, γ-HCH, heptachlor, aldrin, γ-chlordane, α-endosulfan, p,p’-DDE, dieldrin, endrin, β- endosulfan, p,p’-DDD, p,p’-DDT and methoxychlor were identified and quantified using GC-ECD. Samples used for the investigation were collected from Abetifi and Pepease communities in the Kwahu-East and Apesokobi and Worawora in the Biakoye districts of Ghana. The effect of seasonal variations on the level of the organochlorine pesticide (OCPs) residues in the root of Cryptolepis sanguinolenta was also investigated. The mean concentrations of OCPs in the Cryptolepis sanguinolenta samples collected from Biakoye and Kwahu-East districts in the dry season were much higher compared to those of the wet season. The mean OCPs concentrations in dry season were found to range from 0.006 mg kg-1 to 0.061 mg kg-1 while the concentrations for the wet season ranged from 0.001 to 0.011 mg kg-1. The sum of OCPs mean concentrations in the root Cryptolepis sanguinolenta also ranged from 0.033 mg kg-1 to 0.354 mg kg-1, with the highest mean level of 0.354 mg kg-1 detected in samples collected from Biakoye district in the dry season. With the exception of residue levels obtained for the sum of aldrin and dieldrin in Cryptolepis sanguinolenta collected from Biakoye districts in the dry season, the mean OCP residue values obtained were generally below maximum residue limits set by the FAO/WHO Codex Alimentarius Commission and United States/European Pharmacopoeia.
Keywords: organochlorine pesticides, Cryptolepis sanguinolenta, anti-malarial plant, traditional medicine, bioaccumulation, pollution, gas chromatography