Oxidation Communications

Online ISSN: 0209-4541
Publications
Article
In this study, lignin was oxidised to vanillin by means of oxygen in ionic liquid (1,3-dimethylimidazolium methylsulphate) medium. The parameters of the oxidation reaction that have been investigated were the following: concentration of oxygen (5, 10, 15 and 20 ft3 h-1), reaction time (2, 4, 6, 8 and 10 h) and reaction temperature (25, 40, 60, 80 and 100{\deg}C). The Fourier transform infrared spectroscopy, high performance liquid chromatography and ultraviolet-visible analyses were used to characterise the product. The results revealed vanillin as the product obtained via the oxidation reaction. The optimum parameters of vanillin production were 20 ft3 h-1 of oxygen for 10 h at 100{\deg}C. In conclusion, 1,3-dimethylimidazolium methylsulphate could be used as an oxidation reaction medium for the production of vanillin from rubber wood lignin.
 
Article
The kinetics of oxidation of tris(1,10-phenanthroline)iron(II) and tris(2,2'-bipyridine)iron(II) by chromium(VI) in the presence of 1,10-phenanthroline and 2,2'-bipyridine has been studied in sulphuric acid medium. The order of the reaction is unity both in substrate, oxidant and fractional with hydrogen ion. The catalyst (2,2'-bipyridine/1,10-phenanthroline) accelerates the reaction and the order with respect to [catalyst] is fractional. All these reactions follow the Michaelis-Menton behaviour and rate increases with ionic strength. All the reactions obey the following rate law and a generalised mechanism was proposed: rate = k[Cr(VI)]T K1 K 2 [catalyst] [H+]}/1 + K1 [catalyst] + K 1K2 [catalyst][H+] [Fe(L)32+].
 
Article
Catalytic activity of 1,10-phenanthroline (Phen) in HCrO4- oxidation of cyclic ketones has been investigated in acid medium. The Cr(VI)-Phen complex is believed to be the probable electrophile in the catalysed oxidation. The catalytic activity is quite likely to shift the redox potential of the oxidant. The order with respect of substrate and oxidant is found to be one. Increase in acidity as well as increase in the dielectric constant increases the rate of the reaction. The added acrylonitrile has no effect on the reaction rate indicating the absence of free radical mechanism. From the kinetic data the enthalpy and entropy of activation are calculated and a suitable mechanism has been proposed.
 
Article
The complex kinetics of the reaction of ferrocyanide with mixture of ferric ion and 1,10-phenanthroline (phen) resulting in formation of ferroin was studied using HITECH microvolume stopped flow apparatus, at fixed ionic strength (0.1 mol dm-3) under varied acid conditions, which involves the formation of a coordinated complex followed by its reduction. The kinetics was studied with low concentrations of [Fe(III)] and with other reactants in excess and monitoring the formation of ferroin at 510 nm. The reaction followed pseudo-first order kinetics, and had first order dependence on [Fe(III)], third order on [phen]0 and zero order on [ferrocyanide]0. The increase in [H+]0 exerted significant retarding effect on the reaction rate and the reaction recorded a positive salt effect. With no Prussian blue formation, ferrocyanide ion readily reduces ferriin to ferroin. A probable mechanism is proposed and validated by computation for varied acid conditions. Relatively low energy of activation (25 kJ mol-1) and high negative entropy of activation (-212 J K-1 mol-1) agreed well with the proposed mechanism for the formation of compact octahedral complex ion. The proposed mechanism is validated by simulating the curves matching with the experimental profiles at varied acid conditions.
 
Article
Speciation of ternary complexes of Pb(II), Cd(II) and Hg(II) with L-glutamic acid and L-methionine has been studied in varying concentrations (0.0-60.0%) of 1,2-pro-panediol-water mixtures maintaining an ionic strength of 0.16 mol dm-3 (NaNO3) at 303 K. Titrations were carried out in the presence of different relative concentrations of metal (M) to L-glutamic acid (L) and L-methionine (X) ( M : L : X = 1:2:2, 1:2:4, 1:4:2) with sodium hydroxide. Stability constants of ternary complexes were refined with MINIQUAD75. The best-fit chemical models were selected based on statistical parameters and residual analysis. The species detected are MLXH for Pb(II); MLX, MLXH, MLXH2 and ML2X for Cd(II) and MLX and MLXH 2 for Hg(II). Extra stability of ternary complexes compared to their binary complexes is believed to be due to electrostatic interactions of the side chains of ligands, charge neutralisation, chelate effect, stacking interactions and hydrogen bonding. The species distribution with pH at different compositions of 1,2-propanediol and plausible equilibria for the formation of species are also presented.
 
Article
The inhibiting properties of N-phenyl, N'-isopropyl-p-phenylenediamine (4010 NA) and polymerised 1,2-dihydro-2,2,4-trimethylquinoline (Flectol H) mixtures have,been. studied in model reaction of cumene oxidation. It was shown that the system 4010. NA/Flectol H demonstrated maximum, inhibition effect at a ratio of both components 1.7:1.3 weight units (wt.un.). It was found that this stabilising system has. provided high resistance on ozone and, atmospheric ageing of vulcanisates for protectors and sidewalls of tyres, and its optimum dosage in elastomer compositions is 3 wt.un. per 100 wt.un. elastomer.
 
Article
The dependence of quantum yield and decay rate constant on the solvent composition for carbocations generated in the photolysis of 1,2- dihydroquinolines was studied by steady-state and pulse photolysis in binary mixtures of alcohols with solvents of different polarity, proton-donating and accepting ability, and capability to hydrogen bonding. The results were discussed on the basis of the reaction mechanism involving competing reactions of the carbocation combination with two nucleophilic particles, the ROH molecule and the RO - anion. The kinetic behaviour of the carbocations generated from 1,2-dihydroquinolines in the photolysis in solvents mixtures is determined by the polarity, proton-donating and accepting ability, nucleophilicity, as well as the ability to form hydrogen-bonded associates between the solvent molecules and between the solvent and solute molecules.
 
Article
The role of medium polarity on the oxidation of trans-1,2-diphenylethylene and trans,trans-1,4-diphenylbutadiene-1,3 in the medium of solvents with different polarity was studied. It was revealed that the dependences of activation energies of hydroperoxide radical addition to substrate double bond on solvents dipole moment values are linear.
 
Article
The role of non-specific solvation effect during oxidation of trans-1,2-diphenylethylene and trans,trans-1,4-diphenylbutadiene-1,3 in the medium of benzonitrile and toluene was studied. There is a linear dependence of logarithm of the rate constant of hydroperoxide radical addition to substrate double bond in coordinates of the Kirkwood-Onsager equation on medium polarity varying.
 
Article
A comparison of literature-based data on the conversion of glycerol and the selectivity of transformation to 1, 2- and 1, 3-propanediol in the presence of copper, ruthenium, rhodium, platinum, palladium and nickel catalysts in the hydrogenolysis process of glycerol has been presented. On the basis of these data the advantageous parameters of process operation such as the glycerol concentration in a solvent, temperature, pressure, catalyst concentration and the reaction time have been selected.
 
Article
Some 2,5-disubstituted-6-thio-1,2,4-triazolo-[3,2-b]-1,3,4-thiadiazoles have been synthesised by cyclisation of 5-aryloxymethyl-2-(N-pheny1 thiocarbanilido)-1,3,4- thiadiazoles with bromine in carbon tertrachloride, and 5-substituted ary1/aryloxymethyl- 2-(phthalomidomethylamino)-1,3,4-thiadiazoles have been synthesised by refluxing a mixture of 2-amino-5-substituted ary1/aryloxymethy1-1,3,4-thiadiazoles with phthalimide and formaldehyde in ethanol. All these compounds have been assayed for their herbicidal activities against Echinochloa oryzicola, Echinochloa crusgalli, Oryza sativa, Glycine max and antifungal activities against Aspergillus niger and Pyricularia oryzae.
 
Article
The kinetics of oxidation of some 1,2 diols, such as ethane 1,2 diol, propane 1,2 diols, butane 1,2 diols by Ce(VI) in nitric acid medium has been studied at different temperatures. The reaction kinetics showed first order dependence on [oxidant] and fractional order in [diol]. The probable mechanism consistent with the observed kinetic data has been proposed. Increasing [H +] has decreased the rate of oxidation at constant ionic strength and order in [H+] was found to be one. Activation parameters were evaluated using the Arrhenius and Eyring theories.
 
Article
Kinetics of oxidation of thiodiglycollic acid by manganese (III) complex of trans-cyclohexane-1,2-diamine-N, N, N′, N′-tetraacetate (cdta4-) in aqueous medium in the range of pH 2-12 leads to the formation of dithiodiglycollic acid. The reaction is first order with respect to Mn (cdta)- and thiodiglycollic acid. Addition of acrylonitrile gives white polymer which indicates that the reaction proceeded via the generation of free radicals. The reaction has been assumed to proceed via an inner-sphere mechanism.
 
Article
The reaction of ozone with trans-1,2-cyclohexanediol (CHD) in aqueous solution is investigated in pH range 2-11. The products of ozonation are analysed by HPLC and 13C NMR. The main products are ketones, aldehydes, aldo-acids, dicarbonic acids and peroxybridged compounds. The Henri's coefficient of the ozone equilibrium between gas and water phase and the reaction constant of the reaction at room temperature and normal pressure are determined as 0.34 and 1.1 dm 3 mol -1 s -1, correspondingly. The rates of CHD consumption decay, absorption of ozone and formation of ketone were calculated for different values of pH. The mechanism of reaction is proposed.
 
Article
The epoxidation of (Z,E,E)-1,5,9-cyclododecatriene (CDT) to trans-1,2-epoxy-(Z,E)-5,9-cyclododecadiene (ECDD) with hydrogen peroxide in the presence of heteropoly acid: 12-dodecatungstophosphate-H3PW12O40 or 12-dodecamolybdophosphate-H3PMo12O40 as the epoxidation catalyst and cetylpyridinium bromide (CPBr) or chloride (CPCl) as the phase transfer catalyst (PTC) was investigated (in situ method). The results were compared with obtained in the presence of previously obtained catalysts: tris(cetylpyridinium) 12-tungstophosphate-(PCWP-Cl) and tris(cetylpyridinium) 12-molybdophosphate-(PCMoP-Cl) and their counterparts obtained in the presence of CPBr (PCWP-Br and PCMoP-Br).
 
Article
Chlorinated hydrocarbons used as herbicides to control weeds and pests in agriculture that end up in water ways are of menace for aquatic organisms and other users. The reaction of 1,2-dichlorobenzene (DCB) in water with ozone is the focus of the research. The oxidation of DCB in aqueous solutions, as well as in the presence of activated charcoal was studied under acidic, neutral and alkaline conditions. 3,4-dichloro-5hydroxy-2(5H)-furanone and mucochloric acid (2,3-dichloro-4-oxo-2-butenoic acid) were identified to be the main oxidation products with good yields. The effect of presence of other organic solvents, acetic acid and ethyl acetate on the ozonation and the scope to enhance conversion and selectivity efficiencies was also investigated. Both activated charcoal and ethyl acetate facilitated the conversion with improved selectivity towards MCA. Acetic acid had negative effect. Based on the selective nature of the products, molecular ozone is suggested to be the reactive species. For the reactions at alkaline pH with hydroxyl radicals products were less selective.
 
Article
Bis(acetylacetonato)copper(II), which is a common catalyst used in the reactions of diazo compounds, catalyses the oxidation of hydroxy group in α-hydroxyketones such as benzoins leading to the formation of benzils. The reaction takes place both by conventional heating of solution and on solid support by microwave irradiation. The reaction is general to substrates having electron-donating and electron-withdrawing groups.
 
Article
Some new ecologically safe cytokinins on the basis of alkyl esters of m- and p-alkylthioureidobenzoic acids have been studied. The synthesis, chemical structure and cytokinin activity of the new ecologically safe alkylthioureidobenzoic acids, alkyl esters of m- and p-alkylthioureidobenzoic acids (I) and 3-alkyl-4-oxo-2-thion-1,2,3,4-tetrahydroquinazolines (II) with the general formulas (Chemical Equation Presented) where R may be methyl, ethyl, allyl, n-butyl and phenyl; R′ may be hydrogen (H), methyl (Me), ethyl (Et), n-propyl (Pr), isopropyl (i-Pr), n-butyl (n-Bu), isobutyl (i-Bu), n-amyl (n-Am) or isoamyl (i-Am), have been described. The synthesis of II was performed in alcohol solution at room temperature. The relationships between the chemical structure and cytokinin activity of new ecologically safe substances were studied. A high cytokinin activity of some of the compounds has been established applying the highly specific Amaranthus bioassay. A lot of the tested substances manifested a high cytokinin activity which was also determined by the callus tissue bioassay.
 
Article
A simple and green procedure is developed for the liquid phase oxidation of 5-aryl-3-mercapto-1,2,4-triazoles to di-5-aryl(4H-1,2,4-triazol-3-yl)disulphides using NaBr and H2O2 in good to excellent yields. The products are obtained in high purity and yield and characterised by H-1 NMR, IR and mass spectral data.
 
Article
The title compound has been synthesised and characterised by microanalysis, FT-IR and (1H and 13C) NMR techniques. The thermal decomposition of the compound was studied with TG, DTA and DTG techniques under static air atmosphere at different heating rates of 10, 15 and 20 K min -1. The kinetic parameters were calculated using model-fitting (Coats-Redfern, CR) and model-free methods (Kissinger-Akahira-Sunose, KAS; Tang; Flynn-Wall-Ozawa, FWO). The compound decomposed in three stages and the rate of decomposition was very slow in the second stage. The decomposition process was through more than one mechanism in all the stages as evidenced by the data.
 
Article
The kinetics of oxidation of a few cyclic ketones by 1,3-dichloro-5, 5′-dimethyl hydantoin (DCDMH) is reported. The results are interesting as a dualistic pathway involving oxidation of keto-form and the enolic-form simultaneously based upon kinetic observations. The order of reactivity is cyclohexanone > cyclopentanone > cyclooctanone > cycloheptanone. The observed kinetic orders are first order in oxidant, fractional order in substrate, fractional order in H+ in both the oxidation sequences. Suitable rate law is postulated.
 
Article
The kinetics of halogenation of phenol and β-naphthol by 1,3-dichloro-5,5-dimethylhydantoin has been studied in aqueous and aqueous acetic acid systems at varying concentrations of substrate, halogenating agent and H+. The reaction has been found to be first order in halogenating agent and fractional order in substrate to independence at higher concentrations of substrate. The dependence on H+ is inverse fractional under conditions used for the study. The reaction is routed through a charge transfer complex formed between the substrate and the halogenating agent in a slow step formed which breaks down. Composite rate law has been derived and it takes the form: (Equation Presented) The composite rate law explains all the kinetic orders observed and, thus, the Swain's graphical analysis is useful for understanding the mechanistic details of the halogenation process.
 
Article
Oxidation of acetylacetone (AA) and benzoylacetone (BA) by Mn(III) pyrophosphate has been investigated. Benzoylacetone undergoes C-C cleavage while acetylacetone undergoes C-H cleavage. This has been confirmed by product study and supports the proposal that large negative entropy of activation is associated with C-H cleavage and large positive value is associated with C-C cleavage. The energy of activation observed for benzoylacetone is 97.8 kJ mol-1 while for acetylacetone 35.7 kJ mol-1. Relevant mechanisms have been suggested which are consistent with the observed rate laws. In both these oxidations reactions free radical intervention and the Michaelis-Menten type of kinetics have been observed. In similar conditions benzoylacetone reacts faster than acetylacetone. The reactions obey the following rate law: (Chemical Equation Presented) (K is complex formation constant between Mn(III) pyrophosphate and substrate).
 
Article
The electrochemical oxidation of 2-[4′-sulphonamoylphenylhydrazono]-5,5-dimethylcyclohexane-1,3-diones has been studied at solid micro electrodes over a wide pH range. The oxidation takes place in an irreversible, two-electron peak. The products of oxidation were identified by spectral and chromatographic techniques. On the basis of voltammetry, coulometry and product identification a mechanism has been suggested.
 
Article
Kinetic studies on the decomposition of hydrogen peroxide were performed. Two systems were investigated: (i) hydrogen peroxide/sec-butyl alcohol; (ii) hydrogen peroxide/sec-butyl alcohol/1,3-butadiene. The decomposition of hydrogen peroxide was studied in the temperature range of 353-373 K. The Arrhenius parameters of the processes were determined.
 
Article
The kinetics of oxidation of neopentyl glycol and 1,3-butanediol by ditelluratocuprate(III) (DTC) in alkaline medium has been studied spectrophotometrically in the temperature range of 20-40 degrees C. All data were obtained under the conditions of pseudo-first order reaction in [DTC]. It was found that the reaction had fractional order in [neopentyl glycol] and first order in [1,3-butanediol]. Increasing [OH-] and [reductant], the rate constant k(obs) increased, however, k(obs) decreased with increase in [TeO42-]. In addition, the reaction in [neopentyl glycol] has a negative salt effect, but the reaction in [1,3-butanediol] has a positive salt effect. It was experimentally found that the rate of oxidation of neopentyl glycol was higher than that of 1,3-butanediol. The reaction constants of the different steps of the mechanism were calculated. Activation parameters which controlled by slow step of the mechanism were discussed and thermodynamic quantities determined. Thus, the activation parameters at 298.2 K were calculated.
 
Article
Electrochemical behaviour of 2-[4′-sulphonamoylphenyl]hydrazono-1,3- indanediones was studied in the Britton-Robinson buffers of pH 2.5 to 12.0 at dropping mercury electrode and glassy carbon electrode. At dropping mercury electrode a cathodic differential pulse polarographic peak is obtained in the pH range 2.5 to 6.5. Cyclic voltammograms exhibited a well defined, irreversible cathodic and anodic peak at glassy carbon electrode. At pH 6.5 and above the reduction peak exhibited a tendency to split into two peaks indicating that the 4e-/4H+ reduction of 2-[4′-sulphonamoylphenyl] hydrazono-1,3-indanediones occurs in two one-electron and one two-electron steps. Products of controlled potential electrolysis were characterised by elemental and spectral analysis.
 
Article
The kinetics of thallium (III) perchlorate oxidation of some 1,3-diketones viz. acetylacetone and benzoylacetone have been studied in acetic acid - water mixture in the presence of perchloric acid, monitoring thallium (III) iodometrically. The reactions are zero order in oxidant and first order in substrate and perchloric acid. Addition of sodium perchlorate has no effect on diketone - Tl (III) system while added chloride ions retard the rate of oxidation. Effect of variation of dielectric constant of the medium has also been studied. The thermodynamic parameters have been evaluated. A mechanism involving rate determining enolisation has been proposed.
 
Article
The kinetics of halogenation of acetanilide in aqueous acetic acid medium in the presence of pechloric and hydrochloric acids is reported. The order with respect to 1,3-N,N-dichloro-5,5-dimethylhydantoin (DCDMH) is unity. The reactions are found to have complex behaviour on acidity, direct dependence of H+ up to 0.1 mol dm-3 and inverse fractional dependence on H+ over 0.1 mol dm-3. The dependence on substrate is fractional. Addition of Cl- ions has a pronounced catalytic effect. Substituents with electron-releasing groups and electron-attracting accelerate the reaction indicating a complex behaviour. A mechanistic pathway involving the formation of N-chloro intermediate in the equilibrium step followed by intermolecular Orton rearrangement in rate-determining step has been postulated. Swains treatment has been applied to derive a composite rate law. This is in agreement with the kinetic observations.
 
Article
The kinetics of the oxidation of some alpha-amino acids such as glycine, DL-valine, DL-alanine, phenylalanine, arginine, L-glutamic acid, DL-aspartic acid in aqueous acetic acid-sodium acetate mixtures by 1,3-dichloro-5,5'-dimethylhydantoin has been studied. It has been found that the oxidation of the alpha-amino acids with 1,3-dichloro-5,5'-dimethylhydantoin in aqueous HOAc - NaOAc buffer system or any halogen carrying agent most probably follows synchronous oxidative decarboxylation mechanism.
 
Article
Some 2,5-disubstituted aryl-1,3,4-oxadiazolo [3,2-c] thiazoles have been synthesised by cyclisation of 2-(4-substituted aryl)-3-(4-substituted benzamido)-thiazolidin-4- one with conc. H2SO4 with constant stirring in cold and 2-Aryl/aryloxymethyl-5-(2- furyl)-1,3,4-oxadiazolo [3,2-c] thiazoles have been synthesised by the cyclisation of 3-substituted aryl amido/3-substitued aryloxy acetamido-2-(2'-furyl)-thiazolidin-4- ones with conc. H2SO4, with constant stirring in cold. All these compounds have been assayed for their herbicidal activities against Echinochloa oryzicola, Echinochloa crusgalli, Oryza sativa, and Glycine max.
 
Article
The kinetics of halogenation of o- and p-hydroxybenzoic acids,, o- and p-nitrophenols has been studied by using trichloromelamine in 100% acetic acid with varying amounts of perchloric acid. The kinetic orders are first order in the halogenating agent, first order in o- and p-hydroxybenzoic acids, first order in p-nitrophenol and nearly first order in o-nitrophenol. The dependence on acid is first order in o-hydroxybenzoic acid, and fractional order in p-hydroxybenzoic acid, first order in p-nitrophenol and fractional order in o-nitrophenol. An attempt has been made to rationalise the observed results in the light of the Swain's treatment. k(i), k(ii), k(iii) and k(iv) have been evaluated and they are of right order of magnitude for these bimolecular reactions.
 
Article
The kinetics of oxidation of D-glucose by 1,3,5-trichloro-1,3,5-triazine-2,4,6-trione has been studied under catalytic conditions using transition metals like Ru(III), Os(VIII) and Mn(II) in aqueous acetic acid-perchloric acid mixtures. The kinetic dependences in Ru(III) catalysed reactions are diverse - zero order in oxidant leading to first order dependence at higher concentrations of oxidant, zero order in substrate leading to first order at higher [oxidant]. The orders in catalyst and [H+] are one and zero, respectively. The rate decreases with increase in acetic acid. With Os(VIII) the kinetic features are zero order in oxidant, nearly first order in substrate, first order in catalyst and independent of H+. The rate increases with increase in acetic acid. With Mn(II) the dependences are zero order in oxidant, nearly first order in substrate, zero order in Mn(II) and independent of H+. The reaction is insensitive with increase in acetic acid content. All these have been rationalised by postulating suitable mechanistic pathways and rate laws.
 
Article
The kinetics of halogenation of a few anilides using N-2,(NN6)-N-4-trichloro-2,4,6-triamino-1,3,5-triazine (trichloromelamine) in pure acetic acid medium in the presence of perchloric acid is reported. The order with respect to trichloromelamine (TCM) is unity. The reactions are exhibiting differential behaviour on acidity. Acetanilide and p-methyl acetanilide show inverse fractional dependence on acidity whereas p-methoxy acetanilide is found to have direct unit dependence on acidity. p-Nitro acetanilide behaves differently as it shows zero dependence on acidity. Addition of Cl- enhances the rate. The replacement of HClO4 by HCl accelerates the reaction. Substituents with electron-releasing groups and electron-withdrawing groups are both accelerating the reaction indicating a breakdown of rho sigma plot. A suitable rate law has been derived. All the facts have been explained on the basis of a plausible mechanism involving the Orton rearrangement.
 
Article
The data on trans-polymerisation of conjugated dienes (butadiene, isoprene, cis-and trans-isomers of piperylene, chloroprene) by radical, ion and ion-coordinating mechanisms are considered. The factors that forward to formation of 1,4-trans-structures in polydienes macromolecules are analysed. The main attention was given to the catalysts of the Ziegler-Natta type: to the influence of transition and non-transition metals nature, conditions of catalytic complexes preparation and polymerisation on activity and trans-stereospecificity of catalysts, and molecular characteristics of forming polydienes. The correlation between monomer nature and polydienes properties is shown. Application fields for trans-polymers of butadiene, isoprene, pentadiene and chloroprene are presented.
 
Article
The interaction of 1,4-cis-polybutadiene with nitric acid for 0.5 to 950 min and at the temperature range from 20 to 60°C has been studied by employing the differential infrared (IR) spectroscopy method. Initially, electrophilic addition reaction of the nitric acid to the C=C double bonds in the elastomer, resulting in the formation of nitrate ester groups, took place. Depending on the conditions, the reaction was further found to proceed via mixed ion-radical mechanism. As a result, fragments, containing other functional groups, were also formed and simultaneous cis-trans isomerisation reactions occurred as well. A principal scheme for the consecutive formation of the various functional groups was also suggested.
 
Article
A mild and efficient aromatisation of the Hantzsch 1,4-dihydropyridine with potassium peroxomonosulphate-potassium iodide is reported. The oxone-KI system converts 1,4-dihydropyridines to their corresponding pyridine derivatives at room temperature in a 1:1 CH 3CN/H 2O mixture. The ability of various halide salts in the oxidation of 1,4-dihydropyridines was also investigated.
 
Article
A quantitative structure-activity relationship (Qsar) study has been performed on 1,4-dihydropyridine analogues as calcium channel antagonists to understand the structural features influencing the activity of these analogues towards the hypertension. The results showing that lg 1/IC50 activity could be modelled using topological as well as some other parameters, viz. AlogP, BAC, Jhete, W, MR, POL. The predictive ability of the models was checked by cross-validation method.
 
Article
The photochemical properties of 1-aryl-2,4,6-triphenyl-1,4-dihydropyrazines 1 were investigated in conventional solvents. The results demonstrated that 1 were unstable to form N-arylbenzamide 2 and N-arylbenzenecarboximidic acid 3 under irradiation with UV light. The photoreaction mechanism was proposed via a photooxygenation. The photoreaction products were determined by ¹H and ¹³C NMR, high-resolution mass spectrometry (HRMS), and single crystal X-ray diffraction analysis.
 
Article
The interaction of non-filled sulphur-vulcanised elastomer based on cis-1,4-poly-butadiene with nitric acid at 20 and 60°C within the time interval from 30 s to 180 min has been studied by employing the differential infrared (IR) spectroscopy method. The change in the relative content of functional groups versus reaction time was examined. Based on the sequence of the formation of nitro- as well as nitrate ester functional groups, the reaction was found to proceed via mixed ionicradical mechanism even at its initial stage. Higher temperatures favoured the radical mechanism of the process, which facilitated significantly the cis-trans-isomerisation of the residual C=C double bonds in the starting material.
 
Article
Antihypertensive activity of a series of alkyl N-[diphenylalkyl]aminoalkyl-4-aryl-1,4-dihydro-2,6- dimethylpyridine-3,5-dicarboxylates was modelled using distance-based topological indices: Wiener (W), Szeged (Sz), and molecular negentropy (N). The results are compared using mono- and multiparametric regressions.
 
Article
The synthesis of 4-(dimethylamino)-1,4,4a,5,5a,6,11,12a-octahydro-3,6,10,12,12a-pentahydroxynaphthacene carboxamido-methylamines via aminomethylation approaches involving the Mannich reaction is described. The newly synthised Mannich bases are structurally elucidated on the basis of elemental and spectral (UV, IR, (1)H NMR) studies. All the newly synthesised Mannich bases exhibited significant and promising antimicrobial activity against various pathogenic gram-positive and gram-negative bacteria and are found to have low toxicity.
 
Article
The oxidation of (E,E,Z)-1,5,9-cyclododecatriene catalysed by Pd(II)-Cu(II) system has been studied at temperature 373 K and 2.5 MPa air pressure in alcoholic solution. Use of aliphatic alcohols both as solvents and reactants resulted in high selectivities with respect to allyl ethers and ketones while maintaining relatively high cyclododecatriene conversion. A reaction network was presented that explains both the results of this work and earlier results from literature.
 
Article
The paper presents the characteristics of titanium silicalite catalysts prepared in the presence of hexaalkyl-1,6-hexanediammonium hydroxides: [R3N+(CH2)6N+R3]2OH- with the following alkyl groups: CH3-, C2H5-, C3H7-and C4H9-. Syntheses were carried out using hexaalkyl-1,6-hexanediammonium hydroxides or bromides in the mixture with sodium hydroxide. Hexaalkyl-1,6-hexanediammonium dibromides were synthesised by the reaction of corresponding amine with 1,6-dibromohexane. The composition of the catalysts has been determined by XRF method. The absorption band at 960 cm-1 which appeared in IR spectra and band 220 nm in UV-VIS spectra confirmed the incorporation of titanium into the silica framework. The crystalline structure of the catalysts has also been confirmed by XRD analyses. The morphology of the catalysts has been determined by SEM photographs. The catalysts activity was assessed in epoxidation of allyl alcohol with hydrogen peroxide. Keywords: titanium silicalite, synthesis, hexaalkyl-1,6-hexanediammonium hydroxides. * For correspondence.
 
Article
Rare earth tellurites are comparatively new group of inorganic compounds which recently take the interest of many researchers. The perspectives of these compounds is in their application in modern technologies, such as the nanotechnology, silicate industry, as a dielectric and ferroelectric material; in the medicine - as additions to different kinds of drugs for treating hardly curable diseases; and also as an agricultural microfertilisers. The rare earths tellurites of the type Ln(2)Te(4)O(11) were synthesised. Purity and individuality of the tellurites synthesised can be controlled chemically. For reliable assessment of the completeness of the course of chemical reactions and the accuracy of the information obtained, 3 determinations for each tellurite were performed and average values were taken. The results of chemical analyses of the compounds studied were compared with theoretically calculated quantities for the tellurites. The absolute error was determined. The experiment shows that the mechanical mixtures of metal oxide and telluric dioxide are homogenised and meet the stoichiometric composition of the studied compounds.
 
Article
The perspectives of the rare earth tellurites is in their application in the contemporary technologies, such as the nanotechnologies, silicate industry, as a dielectric and ferroelectric material; in the medicine as additions to different kinds of drugs for curing of hard healing diseases; and also as an agricultural microfertilisers. The aim of the present work is to determine experimentally, calculate and predict the specific molar heat capacity (C p) of the rare earth tellurites products of the Ln 2Te 4O 11 type synthesised by us. The compositions studied were of the type Ln 2Te 4O 11 where Ln = Y, Er, Yb. They were synthesised in vacuumed ampoules and characterised by chemical and X-ray analyses. The specific molar capacities (C p) of the compounds studied were determined in the temperature range 399-587 K using differential scanning calorimeter DSC (Setaram, France). The values measured were computer-processed by the linear regression method to obtain empirical formulae for the corresponding compound and the coefficients a, b and c in the equation C p = a + bT + cT 2 were determined. The dependencies of the experimentally measured and the calculated values of C p for the compounds studied Y 2Te 4O 11, and Yb 2Te 4O 11 had regression coefficients R 2close to unity which means that the calculation procedure used was precise and correct. This provided a possibility to employ regression analysis to predict C p in temperature ranges for which there are no experimental data. On the other hand, the specific molar heat capacities calculated allowed determination of the temperature dependences of entropy (AS r°), change of enthalpy (△S T°-△H 298°) and the Gibbs function △G T°), as well as to predict the thermodynamic values in non-studied temperature intervals. The data on the thermodynamic properties were necessary for development of industrial technologies for synthesis of compounds containing rare earth elements and products on their basis with preselected properties.
 
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In this paper we used different topological indices for modelling NMR chemical shift of carbinol carbon. A wide variety of indices like the Weiner (W), the Padmakar Iwan (PI), the Randic connectivity, ( 0χ, 1χ, 2χ 3χ), the Kier and Hall valence connectivity ( 0χ v, 1χ v, 2χ v, 3χ v) and the Balaban indices (J) were used for obtaining statistically significant model. Regression analyses of the statistically significant 6 models were proposed. The predictive power of these proposed models was discussed on the basis of crossvalidation parameters. The results indicate that the best model contains the Balaban, the Weiner and connectivity indices as the most appropriate correlating descriptors.
 
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Inflammatory and immunologic progressions are convoluted in the pathogenesis of cardio vascular disease (CVD). Human leukocyte Antigen-G (HLA-G) is a negative controller of the immunologic reactions. This study evaluates the 14bp Insertion/ Deletion (Ins/Del) HLA-G polymorphism in CVD patients. Genotyping of the 14bp Ins/Del HLA-G polymorphism was performed by polymerase chain reaction (PCR). There is also a large variation of cholesterol level for the both groups CVD (235.3 ± 9.348) and HC (161.8 ± 3.387). It is also indicated that there is significant difference (p < 0.0001) of diabetic patients in glycation level with all other clinical parameters: triglycerides, low-density lipoprotein (LDL), high-density lipoprotein (HDL), glucose, protein, alanine transaminase (ALT), aspartate aminotransferase (AST), alkaline phos-phatase (ALP) and advanced glycation end-product (AGE) products with the healthy donors. There is significant difference (p < 0.0001) in the distribution of HLA-G 14 Ins/Del polymorphism between diabetic patients having CVD and healthy subjects. The frequent regularity of Ins/Del genotype was significantly higher in diabetic patients with CVD compared to the healthy subjects. In conclusion, the study on the significant linkage between the HLA-G Insertion/Insertion genotype and CVD introduces other risk to genetic factors contribution to this common inflammatory disease.
 
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Extracellular rhamnolipids and biopolymer are important fermentation products of Pseudomonas sp. PS-17. In culture broth they form with each other a complex - rhamnolipids/polysaccharide - having emulsifying and surface-active properties. Biosurfactants are produced during the stationary growth phase of Pseudomonas sp. PS-17 on n-hexadecane and mannitol in conditions of aeration. Substantial production of rhamnolipids and biopolymer began at the onset of the stationary phase. The scheme of Pseudomonas sp. PS-17 growth is offered taking into account the stages of synthesis of products. The kinetics of culture growth and synthesis of biosurfactant with determination of specific growth rate (μ), max specific growth rate (μmax), constant of affinity of the cell to substrate (Ks) were studied. These parameters were determined during the exponential-growth phase. The mechanism of inhibition of the process of growth of culture of Pseudomonas sp. PS-17 and bio surfactant production is made out. The periods of induction on kinetic curve of microbial growth of population are defined.
 
Top-cited authors
Mehmet Çetin
  • Ondokuz Mayıs Üniversitesi
Hakan Sevik
  • Kastamonu Üniversitesi
Nikolaos Gougoulias
  • University of Thessaly
Aleksandar Djordjevic
  • University of Novi Sad
Sheila Srivastava
  • Feroze Gandhi College