Classical chemical sciences
The kinetics of interaction between ninhydrin and zinc-dipeptide (glycyl-tyrosine), [Zn(II)-Gly-Tyr]+ complex have been studied in aqueous and in micelles formed by the cationic surface active material, cetyltrimethylammonium bromide (CTAB) at 80 C and pH 5.0. The reaction follows first- and fractional- order kinetics with respect to [Zn(II)-Gly-Tyr]+ and [ninhydrin], respectively, both in the absence and presence of cationic CTAB micelles. The catalytic role of [CTAB] can be related to the extent of incorporation or association of the [Zn(II)-Gly-Tyr]+complex and ninhydrin into the micelles. CTAB micelles decrease the activation enthalpy and make the activation entropy less negative. The micellar catalysis is explained in terms of the pseudo-phase model of the micelles. Binding constants KS for [Zn(II)-Gly-Tyr]+ and KN for ninhydrin with micelles are calculated with the help of observed kinetic data.
Keywords: glycyl tyrosine dipeptide, ninhydrin, micelle, [Zn(II)-Gly-Tyr]+, cetyltrimethylammonium bromide, CTAB
The objectives of the series of reviews are the collection, concise description, comparison and evaluation of the various chromatographic methodologies applied for the separation and quantitative determination of anticancer drugs in various accompanying matrices.
Keywords: synthetic anticancer drugs; natural anticancer agents; liquid and gas chromatographic technologies; electrically driven systems
Chromatographic retention factors were measured for 45 different organic solutes of varying polarity and hydrogen-bonding capability on an anhydrous 1-(2-methoxyethyl)-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate, ([MeoeMPyrr]+[FAP]–), stationary phase at both 323 K and 353 K. The experimental retention factor data were combined with recently published thermodynamic data for solutes dissolved in ([MeoeMPyrr]+[FAP]–) to give the corresponding gas-to-liquid partition coefficients (log K). The water-to-anhydrous ([MeoeMPyrr]+[FAP]–) partition coefficients (log P) were also calculated using published gas-to-water partition coefficient data for the solutes studied. The derived partition coefficients were analyzed in analyzed in accordance with the Abraham model. The Abraham model expressions that were obtained in the present study back-calculate the observed 105 log K and 102 log P values to within a standard deviation of 0.14 and 0.16 log units, respectively.
Keywords: chromatographic retention factors, partition coefficients, linear free energy relationships, ionic liquids
Oxidation of benzyl alcohol and some ortho-, meta- and para-monosubstituted ones by imidazolium fluorochromate (IFC) in dimethyl sulphoxide (DMSO) leads to the formation of corresponding banzaldehydes. The reaction is of first order with respect to IFC. A Michaelis – Menten type of kinetics were observed with respect to the alcohols. The reaction is promoted by hydrogen ions; the hydrogen-ion dependence has the form kobs= a + b [H+]. Oxidation of ,-dideuteriobenzyl alcohol (PhCD2OH) has exhibited a substantial primary kinetic isotope effect (kH/kD = 5.86 at 298 K). The reaction has been studied in nineteen organic solvents and the effect of solvent analysed using Taft's and Swain's multi-parametric equations. The rates of oxidation of para- and meta-substituted benzyl alcohols have been correlated in terms of Charton’s triparametric LDR equation whereas the oxidation of ortho-substituted benzyl alcohols with tetraperametric LDRS equation. The oxidation of para-substituted benzyl alcohols is more susceptible to the delocalization effect than that of ortho- and meta- substituted compounds, which display a greater dependence on the field effect. The positive value of suggests the presence of an electron-deficient reaction centre in the rate-determining step. The reaction is subjected to steric acceleration by the orthosubstituents. A suitable mechanism has been proposed.
Keywords: Correlation analysis; halochromates; imidazolium fluorochromate; kinetics; mechanism; oxidation
A simple and rapid synthetic methodology has been explored exhibiting the use of a magnetically separable copper ferrite (CuFe2O4) nanocatalyst in water for the construction of medicinally privileged quinoxalines under sonication. High catalytic activity and ease of recovery using an external magnetic field are additional eco-friendly attributes of this catalytic system.
Keywords: Magnetically separable nanoparticles, quinoxaline derivatives, one-pot synthesis, ultrasound irradiation
Polymers are macromolecules. They have high molecular weight. They cover a large surface area and hence act as effective corrosion inhibitors. They have been used to control corrosion of various metals such as mild steel, copper, aluminium and stainless steel. They have been used in acidic, basic and neutral mediums. Adsorption of polymers on metal surface obeys various isotherm such as Langmuir, Temkin, Freundlich and Frumkin. Methods such as weight loss and electrochemical studies have been used to evaluate the corrosion inhibition efficiency of polymers. Surface analysis techniques such as FT-IR, SEM and AFM have been used to study the surface morphology of the protective films.
Keywords: adsorption site, active centres, conducting polymers, corrosion inhibition, electron rich, polymers
The Gibbs free energies for KClO3 were evaluated in mixed dimethylformamide (DMF)-H2O solvents at 301.15 K from the experimental solubility measurements. From the experimental the ionic radii ratio of potassium to chlorate ions, the total free energy of the salt is divided into its individual contribution in the mixtures used. Liberation Gibbs free energy for moving KClO3 from standard gas state to standard solution state was calculated according to specific cycle for the solvation process using the solubility product. Also the lattice energy for solid KClO3 (cr) was also calculated and used for further evaluation. The conventional Gibbs free energies for the cation (K+) and the anion (ClO3 -) were estimated theoretically and also the Gibbs free energy of ClO3 - gas was evaluated and all values were discussed.
Keywords: Gibbs free energy, solvation, potassium chlorate, aqueous dimethylformamide
β-Aminocarbonyl compounds are selectively synthesized in high yields under extremely mild conditions via the condensation of aromatic aldehydes, aryl amines and ketones using catalytic amount of iron (III) phosphate under solvent free conditions. The use of readily available iron (III) phosphate as a reusable and recyclable catalyst makes this process quite simple, convenient, and environment-friendly.
Keywords: β-aminocarbonyl compounds, iron (III) phosphate, catalytic synthesis, one pot three component Mannich reaction
A review of the chemistry of H2PO2 (P1), H3PO3 (P3) and phenylphosphonic acid (PPA), and their oxidations by metal and non-metal oxidants is presented.
Keywords: Oxidation, Hypophosphorous acid, Phosphorous acid, Phenylphosphinic acid, Kinetics, Mechanism
A new series of phthalazin-4-one derivatives have been synthesized from the phthalazinone 1 as starting material with some active methylene compounds, Grignard reagents, acetylation, benzoylation and Mannich reaction. A triazolo derivative was also obtained via chlorination of 1 and addition of propionic hydrazide. A C-N bond cleavage occurred accompanied by a good leaving of the phthalimide nucleus upon subjecting 1 to Mannich reaction. A gentle competition between the phthalimide and the phthalzine nucleii was also observed specially upon treatment of Grignard reagent. The structures of the newly synthesized derivatives were confirmed by their elemental analysis, IR, 1H-NMR as well as mass spectral studies of the synthesized compounds were discussed.
Keywords: phthalimides, phthalazinones, Grignard reagents, triazoles, quinazolinones, bond cleavage
The title compound has been prepared in high yield from 9-benzyl-purine derivative by reaction with diethoxymethyl acetate (DEMA). The structure of the tricyclic compound, 7-(2-chlorobenzyl-3H-1,2,4-triazolo[3,1-i]purine (2), was confirmed by X-ray analysis. Semiempirical calculations for predicting geometrical parameters are in excellent agreement with the X-ray crystal structure.
Keywords: diaminomaleodinitrile, purine, iminopurines, triazolopurines, theoretical investigation
Materials and environmental chemistry
There are described the quasi-chemical reactions that take place between radiation defects and impurities in irradiated silicon. It has been experimentally investigated single-crystalline n- and p-type silicon doped, respectively, with phosphorus or boron, irradiated with highenergy electrons or protons and subjected to the high-temperature isochronous annealing. Rates of quasi-chemical reactions are found to be dependent on the charge-states of reactants and then controllable by varying the irradiation conditions – beam-intensity, irradiation temperature and IR light exposure during the irradiation, as well as temperature of annealing of the previously irradiated samples. It is shown that the quasi-chemical reactions can serve as effective tools for tuning the electronic properties of silicon, the basic material of micro- and nanoelectronics.
Keywords: radiation defects in crystals, quasi-chemical reactions, silicon
Corrosion resistance of SS316L alloy in artificial saliva, in the absence and presence of a disinfectant tablet, namely, Almox 250 DT has been evaluated by AC Impedance Spectra. It is observed that when 50 ppm of Almox is added to artificial saliva, charge transfer resistance of SS 316 L increases. Similar observation is made in presence of 200 ppm of Almox also. Hence it is concluded that people having orthodontic wires made of SS 316L, can take the Tablet Almox 250 DT without any hesitation, because in its presence corrosion resistance of SS 316L increases.
Keywords: corrosion resistance of metals, SS 316L alloy, synthetic saliva, orthodontic wires
The paper discusses the kinetics of chromium(VI) ions adsorption from aqueous solutions using chitosan at 25 oC and pH 5. The intraparticle diffusion rate constants (Kid and Ci) determined for chitosan are 0.487 mg g-1 min-1(1/2) and 11.66 mg g-1 respectively . The results shows that the intraparticle diffusion model fits the sorption of chromium(VI) with higher coefficient of determination (R2), thereby indicating the intraparticle diffusion may be rate limiting step for chromium(VI) adsorption. The results from this study indicate that chitosan is a good adsorbent for the removal of chromium(VI) from wastewater.
Keywords: chitosan; intraparticle diffusion rate model; adsorption; chromium(VI); hazardous; wastewater
Colloidal silver nanoparticles were prepared by a conventional reduction of Ag+ ions with NaBH4 and with a novel approach using tannic acid (tannin) as reducing agent of Ag+ ions. The formation of colloidal silver was followed by electronic absorption spectroscopy monitoring the growth of the surface-plasmon resonance band of the nanoparticles. Colloidal silver in tannin is more stable than that prepared with NaBH4 because tannin exerts also a protective colloid function permitting to reach much higher colloidal silver concentration than in the case of NaBH4. Colloidal silver nanoparticles are readily reactive with ozone producing oxidized silver nanoparticles composed by the mixed oxide Ag2O2 formulated as AgIAgIIIO2. If the ozonization is conducted in gentle conditions the oxidized silver nanoparticles remain as colloidal suspension for a certain time. If instead mechanical shaking is applied, the particles coagulate immediately and separate from the liquid medium as a precipitate.
Keywords: silver nanoparticles; colloidal silver; NaBH4; tannic acid (tannin); ozone; oxidized silver nanoparticles
In this study, the removal of thionine dye from aqueous solutions using low-cost materials as adsorbent by a batch system was investigated. Experiments were carried out as a function of contact time, initial concentration, pH and temperature. The equilibrium adsorption of thionine dye on rice husk adsorbent was analyzed by Langmuir, Freundlich and Temkin models. The results indicate that the Langmuir model provides the best correlation of the experimental data. Various thermodynamic parameters such as enthalpy ∆H°, entropy ∆S° and free energy ∆G° were evaluated. Thermodynamic parameters values revealed that the adsorption of thionine onto rice husk is endothermic, spontaneous, with an increased randomness in nature. The results revealed that the thionine is considerably adsorbed on rice husk and it could be an economical method for the removal of thionine from aqueous systems.
Keywords: rice husk, thermodynamic, thionine, isotherm, adsorption
The ability of three chemical oxidants(Fenton’s reagent, Potassium permanganate and Potassium persulfate) to degrade one of the recalcitrant non-hydrocarbon components of crude oil- the porphyrins at three different pH media was investigated in this work and the results showed that the oxidants removed less than 10% of the porphyrins on the average, after two months of treatment. The porphyrins were found to experience degradation of 5%,7% and 4% on the average for the acidic, neutral and basic soils respectively for the vanadyl (VO2+) porphyrins and a reduction of 7%,15% and 7% on the average for the acidic ,neutral and basic soils respectively for the Nickel (Ni2+) porphyrins. This highlighted the recalcitrant nature of porphyrins, but also showed that they are not perfectly so in the presence of chemical oxidants.
Keywords: Vanadyl porphyrins; Fenton’s reagent; potassium permanganate; potassium persulfate; tar balls
Biochemistry, molecular biology and biotechnology
The aim of this study was to find the dynamic of ultrastructural changes of liver at CS and the role of PRP-1 (proline rich peptide) as a protector. Our investigation demonstrated that Mch (mitochondria) of brain are more subject to changes at 2 h of compression than liver Mch, but one time administration of the PRP-1 in a dosage of 10 g/100 g of the animal weight before decompression period prevent the development of the destructive changes of the hepatocytes of the liver and neurons of the rat cortex (injection of PRP on the background of CS prevent progress of ultrastructural changes typical at 4 h of decompression, and leads to Mch fission).
Keywords: Crush syndrome, PRP-1, TEM, neurone, hepatocyte, mitochondria (Mch).
Industrial and engineering chemistry
Continuous catalytic regeneration (CCR) is a key process in petroleum refineries to produce high octane gasoline. In this article, a commercial scale CCR plant with the nominal capacity of 22000 bbl day-1 was simulated using Ref-sim module and Petro-sim simulator. The validity of this plant wide simulator was evaluated by actual test runs obtained during 6 months of operation. Simulation results showed that the AAD % of momentous output variables i.e. outlet temperature of reactors, product volume yield, product RON, H2 purity of recycle gas and coke deposition on the catalyst against actual data were 0.5 %, 0.94 %, 1.098 %, 0.57 % and 0.347 %, respectively. Then, the optimal values for reactor temperatures, feed flow rate and recycle flow rate were determined using sensitivity analysis approach. After setting these decision variables on the proposed optimal values, the actual RON and volume yield of the CCR plant enhanced from 99.55 and 82.04 % to 99.67 and 82.4 %, respectively.
Keywords: Catalytic Reformer, Simulation, Petro-Sim, Sensitivity Analysis, Optimization
The production of phosphoric acid and/or calcium monohydrogenphosphate from Sebaiya phosphate ore was investigated by leaching with nitric acid. Various factors affecting the process such as particle size, leaching time, leaching temperature, phosphate rock/HNO3 ratio and mixing stirring speed and temperature have been studied to estimate the favor phosphate ore dissolution in relation to impurity. These parameters were fixed at a leaching time of 16 min, stirring speed of 400 rpm, temperature of 25 oC, nitric acid concentration of 2.5 % and acid/phosphate ore mass ratio of 25 ml/5 g. The produced aqueous acidic solution was neutralized in such a way that a pure calcium monohydrogenphosphate, CaHPO4, is precipitated to be used as animal fodder. The production efficiency was 97.2 %.
Keywords: Sebaiya phosphate ore, calcium monohydrogenphosphate production, nitric acid leaching