Journal of the Iranian Chemical Society
Volume:5 Issue: 3, Sept 2008

This review on multi-component kinetic-based determinations covers most publications in this field during the period 2000- 2007. The methodologies applied during recent years have been based on differential reaction rates for simultaneous multicomponent analysis. The literature shows a great attempt to apply chemometric methods, such as partial least squares regression, artificial neural networks, H-point standard addition and a new method involving mean centering of ratio spectra in this field. This review also describes some applications of advanced multiway analysis such as PARAFAC and NPLS from 2000 in the multicomponent kinetic analysis.

Copper oxide-titania catalysts with nanocrystalline mesoporous structure were prepared by sol-gel technique using tetra isopropyl ortho titanate (TiPT) as the inorganic precursor and amino-2 ethanol as the swelling agent. Characterization was performed using X-ray diffraction (XRD), fourier transformed infrared spectra (FTIR), scanning electron microscopy (SEM), diffuse reflectance UV-Vis spectroscopy (DRS), and N2 adsorption-desorption measurements. It was found that CuO (0.025-0.1 mol ratio) has some effect on the particle size, surface area, pore-volume, pore-diameter, crystallinity of the particles, and crystalline phase of TiO2 nanocrystalline. The results indicated that 0.1 CuO-TiO2 had higher surface area and total pore volume among all CuO-TiO2 samples. The SBET value of 0.1 mol ratio CuO-load TiO2 sample is approximately similar to that of Degussa P25 while its pore volume (0.1198 cm3 g-1) is larger than Degussa P25 due to production of large number of pores. Therefore, the physical property of 0.1 CuO-TiO2 catalyst is comparable with Degussa P25.At 823K, the 0.1 mol ratio CuO-load TiO2 sample shows the phase transformation from anatase to rutile in the ratio of 1:1.1. The synthesized CuO-TiO2 nanocrystalline will be able to show photocatalytic reaction under visible light.

The catalytic activity of Mn(salen)Cl containing tert-pentyl groups at the 3,5-positions of the salen ligand in the epoxidation of alkenes and hydroxylation of alkanes was studied at room temperature, using sodium periodate as an oxygen source. The effects of various axial ligands were investigated in the epoxidation of cyclooctene. Imidazole, as a strong π-donor ligand, was the best axial ligand. The effect of different solvents was studied in the epoxidation of cyclooctene in CH3CN/H2O solvent mixture. The epoxidation reactions of cyclooctene by different oxygen donors including NaIO4, Bu4NIO4, KHSO5, H2O2, H2O2/urea, NaOCl and tert-BuOOH were also studied and NaIO4 was selected as oxygen source. The presence of bulky substituents in the 3,5- positions of the salen ligand was found to increase the catalytic activity of this complex.

Sulfamic acid (SA) catalyses the nucleophilic opening of epoxide rings by amines leading to the efficient synthesis of β-amino alcohols. The reaction works well with aromatic and aliphatic amines in short reaction times and in the absence of solvent. Exclusive trans stereoselectivity is observed for the ring opening of cyclohexene oxide. This method exhibits excellent regioselectivity for preferential nucleophilic attack at the less hindered position during the reaction with unsymmetrical epoxides.

Much of world`s natural gas reserves are impure, one of the principal contaminants being nitrogen which makes it unsuitable for application and, hence, its separation is important. In this research, clinoptilolite, the most abundant natural zeolite with an open aluminosilicate framework structure and high internal surface area, was modified by ion exchange process to highly exchanged forms of cations of Na+, K+ and H+. The adsorption of N2, CH4 and C2H6 on natural clinoptilolite (Cp) and on its cation-exchanged forms (Na-Cp, K-Cp and H-Cp) was studied at 25 °C. The influence of cation exchange on equilibrium adsorption of N2 showed that selectivity decreased in the order of Cp > Na-Cp > K-Cp and H-Cp has no affinity to nitrogen.

Trimethylsilyl and tetrahydropyranyl ethers were easily converted into their corresponding bromides and iodides with high efficiency and selectivity by N-bromo- and N-iodosaccharins in the presence of triphenylphosphine under neutral conditions. The reaction of trimethyloctyloxysilane as a model compound was studied in different solvents with different ratios of silyl ethers, triphenylphosphine and N-halosaccharin at room temperature, in order to optimize the reaction conditions.

A rapid and easy procedure for direct conversion of TMS-ethers to their acetates catalyzed by cerium(IV) ammonium nitrate (CAN) immobilized on n-butylpyridinium tetrachloroferrate ([nbp]FeCl4) as a room temperature ionic liquid under microwave irradiation was developed. This methodology is enough mild so that the acid sensitive groups such as methoxy, furyl or thiophenyl were remained intact. No side products were observed by this method.

A simple, clean and efficient solvent-free procedure for the preparation of aryl carboxylates is described from the direct reaction of carboxylic acids and phenols, in the presence of 1-methylimidazole as base and tosyl chloride (TsCl) as coupling agent. This method can be easily applied for different substituted phenols and carboxylic acids. It can also be applied for the selective acylation when other functional group such as hydroxyl is present on phenol ring.

The oxidation of alcohols, methoxymethyl ethers, acetals and ketals to their corresponding carbonyl compounds with Fe(NO3)3.9H2O is efficiently promoted in the presence of NaHSO4.H2O. All reactions were performed in the absence of solvent in good to high yields. Availability, stability and non-toxicity of the reagents, mild reaction conditions, absence of solvent, relatively short reaction times, good to high yields of the products, and easy work-up are advantages of the proposed method.

We have used molecular dynamics simulation to study the adsorption isotherms of molecular hydrogen on FeTi at several temperatures ranging from 60 to 100 K. Adsorption coverage, isosteric heat, and binding energy were calculated at different temperatures and pressures. The results indicated that FeTi can be used as an ideal hydrogen storage material. The surface coverage or total amount of hydrogen adsorbed on FeTi is between 0.28 to 0.35.

Novel polyoxometalate-based organic-inorganic hybrid [NH3-CH(CH3)COOH][H3O]8[PMo12O40]3.4NH3CH(CH3)COO was synthesized and characterized by 31P, 1H, 13C NMR and IR spectroscopies, elemental analysis and single crystal X-ray determination. Two of the PMo12O403-anions in the title hybrid are symmetrically equivalent. They are crystallographically independent from the third PMo12O40 3-polyoxoanion, in the case of various interactions with neighboring components in the crystal network (i.e. +NH3-CH(CH3)-COOH and H3O+ cations, +NH3CH(CH3)COO- zwitterions and polyoxoanions). The compound crystallizes in an orthorhombic C222 space group with a = 16.0392(16) Å, b = 34.480(4) Å, c = 12.8968(13) Å and Z= 2.

The coupling of 4-aminoantipyrine (4-AAP) with aniline derivatives catalyzed by ruthenium nanoparticles (Rnp) has been studied by UV-Vis spectroscopy in aqueous medium. The rate constant for antipyrilquinoneimine dye formation depends on the nature of the aniline substituent and the pH, ionic strength and temperature of the reaction medium. The maximum rate constant of the dye formation reaction is observed at pH 3.6. Aniline derivatives with electron donating substituents show higher rate constant values than those with electron withdrawing substituents, with increasing rate constant values in the order: N,N-dimethyl aniline > o-toluidine > o-chloroaniline > m-chloroaniline. With pseudo first order kinetics, the total order is 1.0 + 1.0 + 1.0 = 3.0, which includes the orders with respect to amine, 4-AAP and Rnp. Studies on these effects help to complete the kinetic analysis as well as propose the reaction pathway. Furthermore, TEM measurement confirms that the nanoscalar size of the Rnp is 7 nm.

Present work reports the first total synthesis of a phenylalanine and glycine-rich cyclopolypeptide podacycline B by coupling of tripeptide Boc-L-phe-gly-L-phe-OH and tetrapeptide L-ala-gly-L-thr-L-ile-OMe followed by cyclization of linear heptapeptide segment. The chemical structure of the compound was elucidated by FTIR, 1H NMR, 13C NMR, FAB MS spectral data and elemental analyses. The newly synthesized peptide was subjected to biological screening and found to possess high cytotoxicity against Dalton’s lymphoma ascites (DLA) and Ehrlich’s ascites carcinoma (EAC) cell lines with IC50 values of 13.2 and 15.5 μM, in addition to moderate anthelmintic activity against earthworms M. konkanensis, P. corethruses and Eudrilus sp. at a dose of 2 mg ml-1.

A fast, simple and sensitive square-wave voltammetric (SWV) method for the determination of trace amounts of furazolidone (FZ) in urine is reported. A three-electrode system containing stationary mercury dropping (SMDE) working electrode, Pt auxiliary electrode and Ag/AgCl reference electrode was used throughout. Briton-Rabinson buffer solution is used as both pH adjusting agent and supporting electrolyte. The calibration graph showed good linearity in the concentration range of 20-900 ng ml-1 of furazolidone with a regression coefficient of 0.9996. The equation Δ"(i) = 0.0095CFZ + 0.234 was used for calculation of furazolidone concentration in the sample solution, where CFZ is the concentration of furazolidone in ng ml-1 and Δ"(i) is the difference between voltammogram peak currents of sample and blank solution. The RSD for 8 replicate measurements of a 60 ng ml-1 solution and LOD of the proposed method were found to be 2.2% and 5.2 ng ml-1, respectively. The procedure was successfully applied to the determination of furazolidone in urine samples.

It is known that metalation of (RMe2Si)3CH (R: a = Me, b = Ph) with MeLi in THF yields (RMe2Si)3CLi, which when reacted with allyl bromide, (RMe2Si)3C-CH2-CH=CH2 (1a, 1b) are produced. In this study, although (PhMe2Si)3CLi does not react with benzyl bromide, under the same conditions (Me3Si)3CLi does, giving the expected product. We found that the bromination of 1b was unsuccessful and the reaction of 1a occurs in low yield due to severe steric hindrance. This idea is supported by our results, which show that, when treated with dichlorocarbene and dibromocarbene, 1a and 1b yield the related dihalocyclopropanes. Furthermore, reduction of the obtained products gives the dehalogenated compounds.

Chemical modification of Adenosine Deaminase (ADA) with N-ethyl-5-phenyl isoxazoliom-3-sulfonate (Woodward’s reagent K) (WR-K) was studied using experimental and theoretical techniques. Reaction concentration ranges were 0.8-6 mM WR-K at pH 7.8 and 27°C. It was observed that the maximum number of moles of esterified residues per mol of enzyme (ν) in this concentration ranges is 4. However, esterification of ADA does not affect the activity of ADA, suggesting that the active site residues are not esterified. Similar results were obtained when the active site was blocked with 0.1 mM erythro-9-(2-hydroxy-3- nonyl) adenine (EHNA), followed by esterification, as measured by enol ester formation using absorbance at 340 nm. A theoretical approach was employed to study the modification process using molecular dynamic simulation, MM and QM/MM minimization. A full ASA empirical model and B3LYP method were used to evaluate the relative stability of some species which may arise from the reaction of ADA with WR-K. Theoretical results have shown that five residues (Glu 244, Glu 121, Glu 337, Asp 127, Asp 338) can be possible cases for modification in reaction 1:1 between ADA and WR-K at ν = 1. Glu 121 was possible initially modified in this process. Besides, it is specified that atomic accessible surface area cannot be an appropriate criterion in determination of primary sites which are modified by WR-K. Ultimately, it is clarified that among effective factors in modification of enzyme surface such as atomic accessible surface, stability of modified segment and local residues changes of ADA, latter factor plays a basic role in this process from kinetics and thermodynamics point of view.

The present paper describes the use of methylene blue (MB) as an electroactive label on a pencil graphite (lead) electrode (PGE) to provide a well-defined recognition interface for the detection of HPV target DNA. In order to construct the sensor, a 20- mer single strand oligonucleotide probe related to human papilloma virus (HPV) major capsid protein L1 gene was immobilized on the PGE electrode. Hybridization event between the probe and its complementary sequence was studied by measurement of MB signal accumulated on the PGE using square wave voltammetry (SWV) method. Some hybridization experiments with noncomplementary oligonucleotides were carried out to examine the selectively of the sensor to the target DNA from other DNAs related to Hepatitis C virus (HCV), fungi, and bacterial genes. Moreover, some factors affecting the function of sensor including electrode activation and probe immobilization condition were also investigated. The data showed that the constructed electrode detects the target DNA with detection limit of 1.2 ng μl-1 and discriminates it from various DNAs originated from a wide variety of organisms.

The title complex, [Nd(C6NO2H5)3(H2O)2]nn[ZnCl4]·nCl·2.5nH2O (1), was obtained by hydrothermal reactions and structurally characterized by X-ray diffraction. The crystal structure analysis reveals that the title complex is characteristic of a novel polycationic [Nd(C6NO2H5)3(H2O)2]n 3n+ one-dimensional chain-like structure.

The synthesis of quinoline derivatives via Friedländer method from ortho-aminoaryl ketones in the presence of a catalytic amount of silica sulfuric acid (SSA) under solvent-free condition and microwave irradiation was described. A good range of simple ketones such as cyclohexanone and deoxybenzoin were used.

The structural and electronic properties of 1-(4-substituted-5-hydroxymethyl-tetrahydro-furan-2-ylmethyl)-5-methyl-1Hpyrimidine- 2,4-dione molecules have been investigated theoretically by performing theoretical calculations. The electronic properties and relative energies of the molecules are obtained. It was found that the 1-(5-hydroxymethyl-4-nitro-tetrahydro-furan- 2-ylmethyl)-5-methyl-1H-pyrimidine-2,4-dione molecule have approximately the same structural and electronic properties when compared with the AZT molecules.

This paper describes khellin hydrolysis mechanism using semiemperical PM3 implemented in Gaussian 03 package. The calculations show that in the presence of an acidic media، an enolate molecular ion leads directly to ω-acetokhellinone while in the basic media it leads to khellinone.

The non-rigid molecule group theory in which the dynamical symmetry operations are defined as physical operations is applied to deduce the character Table of the full non-rigid molecule group (f-NRG) of TBA. The f-NRG of this molecule is seen to be a group of order 54 which has 27 conjugacy classes.

Human tyrosinase is often described. Mainly the mutant form, contributing to different forms of albinism appears in literature. This mutant results in a total or parcial lack of color in skin, eyes and hair, occuring among many species. This form of tyrosinase is non-functional. Normal human tyrosinase shows phenole oxidase activity and converts tyrosine to L-3,4-dihydroxyphenylalanine (L-DOPA) and further to dopachrome and is a part of the melanin biosynthesis pathway. There has been a sequence published of the oculocutaneous albinism (OCA 1A) form of human tyrosinase. But the correct sequence is often not known because of base insertions, deletions or single nucleotide polymorphisms (SNPs). This paper wants to contribute to the research about that topic and provides the new and corrected sequence of the human tyrosinase clone of oculocutaneous albinism (OCA 1A).