Revista de Ciencias Químicas

The solvolyses of 4-fluorophenyl chlorothionoformate (1) are studied in fifteen binary aqueous organic mixtures of widely varying nucleophilicity and ionizing power values. The specific rates of solvolyses of 1 are plotted against the specific rates of solvolysis observed for phenyl chloroformate (2) and deviations from the line-of-best-fit are observed in some of the highly ionizing aqueous fluoroalcohol mixtures. An analysis of the solvolytic data accumulated using the extended (twoterm) Grunwald-Winstein equation confirms this deviant behavior and shows that dual bimolecular addition-elimination and unimolecular ionization channels occur in the solvolyses of 1.

A novel synthesis of 3-cyano-2(1H)-pyridinethiones, chromene-3-carbothioamide and chromeno[3,4-c]pyridines were obtained through interaction of N-aryl cyanothioacetamide derivatives with some electrophilic reagents. Most of the target compounds were then evaluated for their antimicrobial and antifungal activities.

The corrosion behavior of 18% Ni M250 grade maraging steel under weld aged condition has been investigated in hydrochloric acid medium. The studies were carried out in hydrochloric acid solutions of different concentrations (0.1 M – 2 M) at different temperatures (30 0C – 60 0C) by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The results showed that the corrosion rate increased with the increase in temperature and with the increase in the concentration of hydrochloric acid in the corrosion medium. Activation parameters were evaluated using Arrhenius equation and transition state equation. The results from the two techniques are in good agreement. The surface morphology of the corroded specimen was compared with that of the un-corroded one by using scanning electron microscopy (SEM).

Novel tetrahydropyrimidines (THP-1 to THP-7) have been synthesized by the reaction of enaminones 1a-d, primary amine and formaldehyde in very good yields and their structures have been established with the help of spectral and analytical data. These tetrahydropyrimidines along with THP-8 to THP-15 previously reported by us were subjected to docking by using fast and flexible method to study their Acetylcholine Receptor (AChR) inhibiting properties. A knowledge-based approach has been followed for assigning proper parameters into the binding site of the protein. Our studies on these THPs reveal that THP-4 possesses best binding conformation within the binding site of the target protein with the energy value of -23.66 KJ/mol.

A method for direct selenium determination in human blood serum by electrothermal atomic absorption spectrometry (ETAAS) was developed. Total selenium was measured by ETAAS employing 10 g of palladium as matrix modifier in a graphite atomizer with pyrolytically coated tubes and Zeeman background correction. Blood serum was diluted 1+2 with 0.1 % v/v nitric acid and 0.1 % Triton X-100. Pyrolysis and atomization temperatures for palladium modifier are 1100 ºC and 2500 ºC, respectively. The measurements were confirmed by the analyses of standard reference material and by the method of standard additions. Reference serum material Seronorm, Trace elements, Serum level 1 (lot JL 4409) was analyzed and the results are in agreement with the certified value. The limit of detection of the direct ETAAS based on 3σ of the blank signal is 0.60 g L-1 Se in blood serum samples. The precision of the method ranges from 2.06 % to 5.95 %. The obtained data from the selenium concentrations in serum samples from 83 patients show that the content of selenium is relatively low, ranging from 43.91 ± 4.80 μg L-1 for female to 45.21 ± 5.60 μg L-1 for male.

The adsorption and transformation of K2Cr2O7 at natural hermit crab shell powder was studied by UV-visible spectrophotometry. K2Cr2O7 is adsorbed at natural hermit crab shell powder, and follows the Freundlich adsorption model with the adsorption constant of KF=888.8 and adsorption free energy change of 16.83 kJ.mol-1. The adsorbed K2Cr2O7 is catalytically transformed into K2CrO4 in moderate conditions by natural hermit crab shell powder with the apparent first-order rate constant of 0.0219 s-1, and equilibrium constant of K=2.27×1012 M-1.

Thermoplastic Polyurethane (TPU) is a highly versatile material with superior physical properties but high cost. Melt blending of TPU with Polyolefins (PO) can lower the cost and improve mechanical and chemical properties. Since TPU and PO are completely immiscible polymers, property enhancement cannot be attained. Effect of incorporation of Polypropylene Copolymer (PPCP) as compatibilizer on the miscibility of the blends and effect of calcium carbonate as filler to enhance the mechanical properties were studied. Blends were produced by melt mixing using a single screw extruder. Miscibility studies were done using Scanning Electron Microscope (SEM) and thermal characteristics were determined using Differential Scanning Calorimeter (DSC). Mechanical properties like tensile strength, impact strength, flexural strength and hardness were also studied using Universal Testing Machine (UTM). The results show that the blend having 20% loading of polyurethane (PU) with suitable compatibilizers and calcium carbonate gives excellent performance in all aspects.

Some novel pyrazoles, thiazolopyrimidine, triazolopyrimidine derivatives containing naproxenoyl moiety were synthesized from the reaction of enaminone derivative 2 with some hydrazines and aminoheterocyclic compounds. Also, some thiazoles were obtained via condensation of acetyl derivative 1 with thiosemicarbazide followed by in situheterocyclization with α-halogenated reagents. Most of the target compounds were then evaluated for their animal toxicity, analgesic and anti-inflammatory activities as NSAIDs.

Cancer is a major cause of death and the number of new cases as well as the number of individuals living with cancer is expanding continuously. Due to the enormous propensity of plants that synthesize mixture of structurally derived bioactive compounds, the plant kingdom is potentially diverse source of chemical constituents with murine leukemia activity. Plant derived compounds have played an important role in the development of several clinically useful anticancer agents having activity against murine leukemia. These include vinca alkaloids, lignans, terpenoids, quinines and phytochemicals such as flavones, flavonoids, flavonol. The active compounds which have been isolated from various plant sources are listed, classified and discussed in terms of their activity against murine leukemia cells. Structure-activity relationship has been studied for further development of compounds which show activity against leukemia cells.

In the present investigation, the powder of mosambi fruit peelings (PMFP) was used as an inexpensive and efficient adsorbent for Ni (II) removal from aqueous solutions. The influence of physico-chemical key parameters such as the initial metal ion concentration, pH, agitation time, particle size and adsorbent dosage has been considered in batch tests. Sorbent ability to adsorb Ni (II) ions was examined and the mechanism involved in the process investigated. The optimum results were determined at an initial metal ion concentration of 50 (mg L-1), pH=4, agitation time – 90 min, an adsorbent dose (125 mg/50 ml) and the particle size (0.6 mm). The % adsorption, Langmuir constants [Q0=29.41(mg/g) and b=0.4789(L/mg)], Freundlich constant Kf= 23.92(mg/g) and n=2.24(L/mg), Lagergren rate constants [Kad (min-1) = 4.37 x 10-2] for [Ni (II)] 50 (mg L-1), were determined for the adsorption system as a function of sorbate concentration. The equilibrium data obtained were tested using Langmuir, Freundlich adsorption isotherm models, and the kinetic data obtained were fitted to pseudo first order model.

Chalcones, precursors of open chain flavonoids and isoflavonoids present in edible plants, and their derivatives have attracted increasing attention due to numerous potential pharmacological applications. They have displayed a broad spectrum of pharmacological activities. Changes in their structure have offered a high degree of diversity that has proven useful for the development of new medicinal agents having improved potency and lesser toxicity. The present review highlights the recently synthesized chalcones and their derivatives possessing important pharmacological activities.

The new mononuclear neutral metal complexes of the type [M(L)2(H2O)nXn] (where n= 0,1,2…; X= Cl; ½ SO4; CH3COO; Br) by using the metal(II/III) salts {M = Cu(II), Co(II), Ni(II), Pd(II) and Ru(III)} with the Clomiphene citrate (L) were synthesized. The ligand and its complexes were characterized by elemental analysis, infrared, ESR, 1H-NMR, electronic spectral studies and magnetic susceptibility measurement, which reveals that L acts as a monodentate ligand. They simultaneously give Thermogravimetric and Differential Thermal Analysis patterns of the complexes recorded at heating rate of 10 °C min-1. The antimicrobial activity of ligand and its metal complexes were evaluated against Gram positive and Gram negative bacteria.

A simple method has been developed for the separation of Gd(III) in hippuric acid medium by using poly[dibenzo-18-crown-6] as stationary phase. The effect of hippuric acid concentration, different eluting agent, foreign ions etc. was studied and the optimum conditions were established. Breakthrough capacity of poly[dibenzo-18-crown-6] for Gd(III) was found to be 0.572±0.01 mmol/g of crown polymer. The separation of Gd(III) from other elements in multicomponent mixtures has been achieved. The method was extended for determination of Gd(III) in real sample. The method is simple, rapid and selective with good reproducibility (approximately ±2%).

Conductive polymers are a new class of materials, which exhibit highly reversible redox behavior and unusual combination of properties of metals and plastics. The conductivity of a polymer can be increased several-fold by doping it with a suitable dopant. Doping plays a very important role to convert the polymer into conductive form. In this work an attempt has been made to synthesize polyaniline chemically with various types of dopant acids such as inorganic acids like sulphuric acid , organic acids like p-Toluenesulfonic acid, Camphorsulfonic acid and metal Lewis acids like Auric acid which act as an oxidative agent as well as a secondary dopant to result in a Polyaniline/Gold nanocomposite. Polyaniline (PANI) was chemically synthesized by oxidative polymerization of aniline in different acid dopants. The influence of concentration of dopant acids during polymerization of aniline was studied. The level of doping and nature of the polymer formed was studied using UV-Visible Spectroscopy. FTIR spectra show that the incorporation of Au seems to be effective for better conductivity of the polymer samples. XRD study confirms the presence of Au in the polymer sample in nanometer scale.

The electrical conductivity of aqueous solutions of decyl- (C10), dodecyl- (C12), tetradecyl- (C14) and hexadecyl- (C16) triphenylphosphonium bromides (TPPBr) was measured at various temperatures. From the conductivity data the critical micelle concentration cmc, and the effective degree of counter-ion binding β, were obtained at various temperatures using a simple non-linear function obtained by direct integration of a Boltzmann-type sigmoidal function. The thermodynamic parameters om G  , om H  and om S were estimated from the temperature dependence of the equilibrium constants for the micellization of each surfactant using the phase separation model. The stability of the micellization process for these surfactants is both enthalpy and entropy controlled. The resulting om H  and om T S plots showed significant correlation, an indication of enthalpy-entropy compensation in the micellization process. The intrinsic enthalpy of micellization H* varies linearly with the number of carbon atoms in the chain length of the surfactants

The effect of processing parameters such as temperature, steam injection rate, and inert carrier gas flow rate on DVB and ethyl vinyl benzene (EVB) production rate was investigated and discussed in isothermal condition and atmospheric pressure in an experimental scale packed bed reactor. The results show that the temperature increases the DVB production rate significantly

Quinazoline and their fused-ring systems are well known for their potential biological activity. Inspired by this and in view of the usefulness of heterocyclic thiols as vulcanization accelerators, new derivatives viz. Quinazoline-2-thiols were prepared. These were synthesized by the condensation of 2-[isothiocyanato(substituted phenyl)methyl]-3,4-dihydronaphthalene-1(2H)-one with primary aromatic amines. All the prepared compounds have been characterized by elemental analysis, IR and mass spectroscopy

The metal taking capacity of several types of biomass, agro products and by-products has gained attention during recent years. Coconut shell powder was chosen as the biosorbent for the removal of Cu (II) from aqueous solutions. The adsorption capacity of this sorbent was investigated by batch experiments. High adsorption (>90 %) is achieved in the present study. The influence of pH and particle size was studied and adsorption isotherm models were fitted. An appropriate kinetic model was also attempted.

The reactivity of 2,3-pyridine dicarboxylic anhydride towards some nitrogen nucleophiles under different conditions was studied. Thus, the reaction of anhydride with substituted anilines (X = 3-COOH, 4-COOH, 4-COOC2H5, 2-OC2H5, 4-OC2H5) in acetic acid at room temperature or toluene under reflux afforded arylcarbamoylpyridinecarboxylic acid. Repeating the same reaction under heating gave rise to a mixture of cyclic imide and nicotinamides. On the other hand, treatment of anhydride with binucleophiles (1,4-phenylenediamine, benzidine, 4,4`-diaminodiphenyl-sulfone) in glacial acetic acid at room temperature (or toluene under reflux) afforded pyrrolopyridine derivatives rather than carboxamide derivatives. The reaction of anhydride with binucleophiles in acetic acid under reflux afforded nicotinamide derivatives. Antimicrobial activities of some selected compounds were screened.

A novel 3-amino-4(3H)-quinazolinone was synthesized via two routes. The first route involved interaction of 2,3-pyridine dicarboxylic anhydride with anthranilic acid in acetic acid under reflux to give the amide derivative which was subjected to cyclodehydration and treatment with hydrazine hydrate. The second route involved preparation of amide by treatment of 2,3-pyridine dicarboxylic anhydride with methyl anthranilate in
glacial acetic acid under reflux, then treated with hydrazine hydrate. Treatment of 3-amino-4(3H)-quinazolinone with isocyanate, isothiocyanate,ethyl chloroacetate and diethyl malonate gave urea, thiourea, thiazole and pyrimidine derivatives, respectively. In addition, some bisquinazolines were synthesized. Antimicrobial activities of some selected compounds were screened.

An efficient and operationally simple reaction is shown between substituted 2-acetyl-1-naphthol/2-acetyl-1-naphthol and different substituted benzaldehydes in presence of base afford chalcones in quantitative yield using grindstone technique. Mild reaction condition, no need of catalyst, non-hazardous and environmentally safer, giving excellent yield in short reaction time, are notable advantages of this method.

Novel oxovanadium(IV) complexes (1-4) with 2-methyl-3-(pyridine-2-ylmethyleneamino)quinazolin-4(3H)-one (L1) or3-(2-hydroxy-3-methoxybenzylideneamino)-2-methylquinolin-4(3H)-one (L2) were synthesized and characterized by elemental analysis, IR, 1H-NMR, electronic spectra, molar conductance and thermal studies. Based on the above spectral studies, the complexes have the general formula [VO(L1)2] (1), [VO(L1)phen] (2), [VO(L2)2] (3) and [VO(L2)phen] (4). The synthesized compounds were tested for antimicrobial activity by disc diffusion method. The results indicate the enhanced activity of metal complexes over their parent ligands. The DNA binding and nuclease activity of the synthesized compounds were also studied. The investigation of the interaction of the complexes with calf thymus DNA has been performed with absorption spectroscopy which showed that the complexes are avid binders of calf thymus DNA. Also, the interaction of the oxovanadium(IV) complexes with plasmid DNA (pUC 19) was studied using agarose gel electrophoresis. The results revealed that these complexes could act as effective DNA cleaving agents resulting in the nicked form of DNA (PUC 19) under physiological conditions. The gel was run both in the absence and in presence of the oxidizing agent.