Journal of the Iranian Chemical Society
Volume:4 Issue: 4, Dec 2007

In this short review, we wish to present an overview of the applications of hydrated, ferric perchlorate, Fe(ClO4)3.XH2O as an available and inexpensive reagent amd catalyst in organic synthesis.

Dihydropyrimidinones, bis(indolyl)methanes, and N-alkyl and N-arylimides were synthesized efficiently under mild reaction conditions in the presence of two types of ionic liquids. In each section, effects of different ILs on the yield of reactions were investigated. The use of ionic liquids offer improvements for the synthesis of title compounds with regard to the yield of products, simplicity in operation, short reaction times and green aspects by avoiding toxic catalyst and organic solvents.

A series of methyl 3,5-bis(3,4,5-trialkyloxybenzoylamino)-4-methylbenzoates (alkyl = CH3(CH2)n-1, n = 8, 10, 12, 14 and 16) exhibits mesomorphic behavior at temperatures between 120 and 240 °C. The liquid crystalline properties have been characterized using differential scanning calorimetry, optical polarization microscopy and X-ray diffraction. The molecules stack in columns which pack under hexagonal symmetry. Variable temperature infra-red absorption measurements provide evidence of intermolecular hydrogen bonding between the amide entities in both the crystalline and liquid-crystalline phases.

A novel diclofenac ion-selective electrode has been prepared and used in pharmaceutical analysis. The ion-associate of diclofenac with basic dye (crystal violet) was used as the membrane carrier. Among the four different solvent mediators tested, dibutylphthalate (DBP) exhibited proper behavior including the Nernstian slope of the calibration curve, fast response time and good reproducibility of the emf values. The electrode exhibits a Nernstian slope of 59 ± 1 mV decade-1 for diclofenac in the concentration range 5.0 × 10-5-5.0 × 10-2 M with the limit of detection of 2.5 × 10-5 M. The electrode displays good sensitivity with the respect to a number of common inorganic and organic species. It can be used in a pH range of 6-11. The membrane sensor was successfully applied to the determination of diclofenac in capsules and for its recovery from urine samples.

The kinetics and mechanism of oxidation of aspartic acid by the bis(hydrogen periodato) complex of Cu(III), [Cu(HIO6)2]5-, is studied in an alkaline medium. The reaction rate is first order with respect to Cu(III) and fractional order with respect to aspartic acid. The value of the observed rate constant is found to decrease with the increase in concentrations of either OH- or IO4-. There is a positive salt effect, and the free radical has been determined. In view of these kinetics phenomena, a plausible mechanism is proposed and the rate equations derived from the mechanism can explain all experimental results. The activation parameters along with the rate constants of the rate-determining step are calculated.

A two-dimensional self-assembled proton-transfer compound, (creatH)+(pdtcH)-, L, was synthesized from the reaction of pyridine-2,6-bis(monothiocarboxylic) acid, (pdtcH2), and creatinine, creat, and characterized using IR, NMR, UV spectroscopy and X-ray crystallography. The anionic and cationic components self assemble two-dimensionally via ion-pairing, H-bonding and π-π stacking and, therefore, parallel sheets are formed. The spectrometric and potentiometric pH titrations indicate that the abundant proton transfer species present at pH < 4.5 is (creatH)+(pdtcH)-, in support of the single crystal X-ray structure. Ab initio method, DFT (B3LYP), was applied for achievement of the barrier energies of proton transfer processes and geometric parameters of transition states.

We investigated the adsorption of hydrogen atoms on metallic single-walled carbon nanotubes using ab initio molecular dynamics method. It was found that the geometric structures and the electronic properties of hydrogenated SWNTs can be strongly changed by varying hydrogen coverage. The circular cross sections of the CNTs were changed with different hydrogen coverage. When hydrogen is chemisorbed on the surface of the carbon nanotube, the energy gap will be appeared. This is due to the degree of the sp3 hybridization, and the hydrogen coverage can control the band gap of the carbon nanotube.

A microwave-assisted method for the synthesis of 2-substituted benzimidazoles in the presence of alumina-methanesulfonic acid (AMA) is reported. In addition, by this method some new bis-benzimidazoles from the direct reaction of phenylenediamine and dicarboxylic acid under microwave irradiation in good to excellent yields are described.

Complexation of osmium tetroxide (OsO4) with pyridine and its substituted derivatives (i.e. 4-picoline, 3 -picoline, 4-tert-butylpyridine, methyl nicotinate, 3,4-dimethylpyridine, 3-chloropyridine, and 3-phenylpyridine) has been studied at different temperatures in benzene. Spectrophotometric measurements have been carried out to obtain the equilibrium constants and thermodynamic parameters. The equilibrium constants of the resulting 1:1 complexes are found to vary in the order 3,4-Me2Py > 4-tBuPy > 4-MePy > 3-MePy > Py > 3- PhPy > 3-C(O)OMePy ≈ 3-ClPy. All complexes are enthalpy stabilized whereas the entropy changes counteract the complexation. The results are discussed in terms of different basicities of the substituted pyridines.

This investigation potentiodynamically evaluates the corrosion behavior of a high strength titanium alloy, VT-9, in 4 M sulfuric acid solution containing different concentrations (10, 20, 30 ppm) of the organic inhibitor, 2-phenyl-4-[(E)-1-(4-sulfanylanilino)methylidene]-1,3-oxazole-5(4H)-one (L-SH), at different temperatures (293, 303 and 313 ± 1 K). The open circuit potential values noted before and after each experiment varied appreciably with time. These values, in the presence of L-SH, were negative before polarization, but after completion of the experiment turned positive and remained stable over a long period of time. The cathodic current density values increased with increasing cathodic potential (more negative). The corrosion potential (Ecorr) increased remarkably with the addition of L-SH. The corrosion current densities (Icorr), critical current density (Icr), and passive current density (Ip) all decreased when L-SH was used. However, only the decrease in the Icorr with increasing amounts of inhibitor was significant compared to that of Icr and Ip. L-SH expanded the range of the passive potential. SEM micrographs and open circuit potential measurements revealed the formation of a uniform and protective film on the alloy surface in the presence of L-SH, which acted as an efficient inhibitor.

A simple, rapid, and sensitive spectrophotometric method for the trace level determination of beryllium based on the formation of a 1:2 complex with anthralin (1,8-dihydroxyanthrone) as a new reagent is developed. A spectrophotometric method was used to determine the acidity constant and stepwise proton dissociation of the reagent. The experimental conditions for determining beryllium including the influences of pH, reagent concentration and time were evaluated and optimized. Under the optimum experimental conditions, the molar absorptivity of the complex is 0.47 × 104 l mol-1 cm-1 at 545 nm. Calibration graph was linear in the range of 0.04-1.04 µg ml-1 with a detection limit of 0.012 µg ml-1 and a %RSD of 0.43%, for 5 replicate determinations at 0.48 µg ml-1 of Be(ΙΙ). The interferring effect of some cations and anions was also studied. The method was applied for the determination of beryllium in beryl, silicate rock and alloys. Ethylenediaminetetraacetic acid (EDTA) was used for masking interfering ions.

An efficient, clean and very simple procedure for the synthesis of protected β-amino acids is described. Michael addition of sulfonamides to α,β-unsaturated esters in the presence of K2CO3 and tetrabutylammonium bromide (TBAB) under microwave irradiation affords the title compounds in good to high yields and short reaction times. This new method affords protected β-amino acids in high yields and short reaction times.

A spectrophotometric study of the kinetics and mechanism of the oxidation of malic acid (Mal) by chromium(VI) catalyzed by 2,2′-bipyridyl (bpy) in aqueous acidic medium was conducted in a temperature range of ~298 to 313 K. This reaction was found to be pseudo-first order with respect to Cr(VI) and first order with respect to malic acid. Under the conditions of the pseudo-first order ([Mal]o >> [Cr(VI)]o), the observed rate constant (kobs) increased with the increase in [H+] and [bpy]. There was a weak negative salt effect. Based on the experimental results, a possible reaction mechanism for this oxidation catalyzed by bpy is proposed. The rate equation derived from this mechanism can explain all the experimental phenomena.

Designing of new inhibitors to human immunodeficiency virus-1 reverse transcriptase (HIV-1 RT) is one of the important research area in AIDS therapies. Non-nucleoside inhibitors of reverse transcriptase (NNIRT) are attractive drug candidates for their unique binding site to the reverse HIV-1 RT and less adverse side effects. The effect of expansion of diazepine ring from seven to eight in some tetrahydroimidazo [4,5,1-jk][1,4]benzodiazepin-2(1H)-thione (TIBO) derivatives as NNIRT has been investigated by docking procedure. Sixteen conventional TIBO derivatives with known HIV-1 RT inhibitor activity were selected and their β-ring was expanded to eight. The three-dimensional (3D) geometry of the molecules was optimized by AM1 semi-empirical method and then interacted with the HIV-1 RT enzyme using Autodock program. Twelve out of sixteen of the new molecules were docked into the enzyme. The resulted free energies of docking indicated that the newly proposed molecules bond to the enzyme with comparable tendency in relative to their corresponding conventional homologous. It was found that three new compounds bind to the receptor stronger than that of their corresponding 7-membered ring derivatives and can be considered as new candidate for synthesis.

A simple and selective method for rapid extraction and determination of trace amounts of iron(III) using octadecyl-bonded silica membrane disks modified with 2-mercaptopyridine-1-oxide and flame atomic absorption spectroscopy is presented. The factors influencing extraction efficiency were evaluated, including the nature of the counter anion, pH of the sample solution, amount of ligand, flow rate of the sample and type of stripping solution. The maximum capacity of the membrane disk, modified by 10 mg of the ligand, was found to be 926 ± 6 μg of iron(III). The breakthrough volume was greater than 2500 ml. Iron(III) was completely recovered (>99%) from water with a preconcentration factor of more than 166. The limit of detection of the proposed method was 0.63 ng ml-1. The various cationic interferences had no effect on the recovery of iron(III) from the binary mixtures. The proposed method was applied to the determination of iron(III) from three different water samples.

A novel pseudo four-component condensation reaction for the efficient synthesis of 2λ5-[1,2]oxaphosphinin compounds using triphenylphosphine and ethyl bromoacetate in the presence of electron-deficient acetylenic esters without using any catalyst and activation is reported. Fully functionalized 2λ5-[1,2]oxaphosphinin derivatives can be prepared from simple and readily available precursors under neutral conditions.

The H-point standard addition method (HPSAM) was applied to the simultaneous determination of zinc(II) and cobalt(II). This method is based on the difference in the absorbance of methylthymol blue complexes of Zn(II) and Co(II) at pH 6 using different wavelength pairs. The results showed that Zn(II) and Co(II) can be determined simultaneously with concentration ratios of 20:1 and 1:7.5. Under working conditions, the proposed method was successfully applied to the simultaneous determination of zinc and cobalt in synthetic, drinking water and vitamin samples.

The tetravalent metal acid (TMA) salt amorphous zirconium phosphate (ZP), an inorganic ion exchanger, has been synthesized by sol-gel method. The material has been characterized by elemental analysis (ICP-AES), thermal analysis (TGA, DSC), FT-IR and X-ray diffraction studies. Chemical resistivity of the material in various media-acids, bases and organic solvents has been assessed. The Na+ ion exchange capacity (IEC) and the effect of heating on the IEC have been determined, and showed the distribution and elution behavior of ZP towards several metal ions in different electrolyte media/concentrations. Based on the distribution studies, a few binary metal ion separations have been achieved.