J. Serb. Chem. Soc. 75 (2) 157–163 (2010)
UDC 547.11:541.57+547.37+547.211–327:539.2; JSCS–3948; doi: 10.2298/JSC1002157J; Original scientific paper

N–H•••O hydrogen bonding. An FT-IR, NIR study of N-methylformAMide–ether systems
BRANISLAV JOVIĆ, ALEKSANDAR NIKOLIĆ, ERNA DAVIDOVIĆ* and SLOBODAN PETROVIĆ**
Department of Chemistry, Faculty of Sciences, University of Novi Sad, 21000 Novi Sad, Serbia

*Lavoslav Ružička Polytehnic of Vukovar, 32000 Vukovar, Croatia

**Faculty of Technology and Metallurgy, University of Belgrade, 11000 Belgrade, Serbia

(Received 7 March, revised 3 September 2009)

This paper reports the results of an FT-IR and NIR study of N-methylformAMide in carbon tetrachloride solution in presence of ethers as the O--electron donors, i.e., diethyl ether (DEE), diisopropyl ether (DiPE), methyl t--butyl ether (MtBE), dibutyl ether (DBE), dipentyl ether (DPE), tetrahydro-furan (THF) and tetrahydropyran (THP). The spectroscopic characteristics of the N–H•••O hydrogen bonded complexes are given. In addition, the equilibrium constants for 1:1 complex formation were determined at 25 °C using Mid-IR and NIR measurements.

Keywords: hydrogen bonding; N-methylformAMide; ethers molecular complex.

J. Serb. Chem. Soc. 75 (2) 165–173 (2010)
UDC 547.458.6+66.095.11+547.292–312; JSCS–3949; doi: 10.2298/JSC1002165H; Original scientific paper

An efficient acetylation of dextran using in situ activated acetic anhydride with iodine
MUHAMMAD A. HUSSAIN, DURE SHAHWAR, MUHAMMAD N. TAHIR*, MUHAMMAD SHER, MUHAMMAD N. HASSAN and ZAKIA AFZAL
Department of Chemistry, University of Sargodha, Sargodha 40100, Pakistan

*Institute of Inorganic and Analytical Chemistry, Johannes Guttenberg University, Duesbergweg 10–14, 55099, Mainz, Germany

(Received 7 April, revised 2 June 2009)

A facile, efficient, cost-effective and solvent-free acetylation method has been developed for the acetylation of dextran. Dextran acetates were successfully synthesized using different molar ratios of acetic anhydride in the presence of iodine as a catalyst without the use of any solvent. The reactions were realized at 50 °C for 3 h under stirring and nitrogen. This efficient method yielded highly pure and organosoluble dextran esters. The reaction appears highly effective for obtaining higher degrees of substitution (DS) with great efficiency. Under solvent-free conditions, dextran triacetates were efficiently synthesized. It was also observed that the molar ratio can easily control the DS of pendant groups onto the polymer backbone. Hence, a range of products with varying DS were successfully designed, purified and characterized. Covalent attachment of the pendant groups onto the polymer backbone was verified by spectroscopic techniques. Thermogravimetric analysis indicated that the obtained dextran esters were thermally as stable as dextran. The DS of the pendant groups onto the polymer backbone was calculated using standard acid base titration after saponification. Furthermore, all products were thoroughly characterized by thermal analysis (TG and DTG), and FT-IR and ¹H-NMR spectroscopic analysis.

Keywords: acetic anhydride; acetylation; dextran; iodine; polysaccharide.

J. Serb. Chem. Soc. 75 (2) 175–183 (2010)
UDC 54.05+547.495.2/.9:664.644.7:678.061; JSCS–3950; doi: 10.2298/JSC01002175P;  Original scientific paper

Immobilization of urease in alginate, paraffin and lac
KESPI PITHAWALA, NEELAM MISHRA* and ANITA BAHADUR*

Department of Biology Gujarat college, Ahmedabad-15, India

*Department of Zoology, P. T. Sarvajanik College of Science, Surat, 395001, India

(Received 14 May, revised 16 July 2009)

The enzyme urease (EC.3.5.1.5) from jack bean meal was immobilized by various techniques, such as entrapment in calcium alginate gel spheres in aqueous suspension; lac impregnated muslin cloth as dry films and by embedding in paraffin wax impregnated muslin cloth. The activity of the free and immobilized enzymes as a function of pH, temperature, storage stability, kinetic parAMeters and periodic use were compared. The immobilized enzyme showed good storage stability. After repeated use, the alginate beads turned brown and deteriorated, hence the storage stability was not good. The paraffin films were preserved dry because during wet preservation, the film slightly softened and the protein leached out slightly. The alginate beads had moderate mechanical stability. The lac films were tougher than the paraffin wax films in terms of mechanical stability. The K_m and V_max values were altered after immobilization. The K_m values for calcium alginate and lac were low, while it was larger in paraffin film as compared to the free enzyme. This may be due to the fact that immobilization on calcium alginate and lac in presence of CaCl₂ and methanol exposed certain active sites of the urease. While immobilization on paraffin masks the active sites and may lead to reduced binding of the substrate.

Keywords: enzyme; immobilization; urease; calcium alginate; paraffin wax; lac.

J. Serb. Chem. Soc. 75 (2) 185–194 (2010)
UDC 577.152:663.12:577.152.1+663.51; JSCS–3951; doi: 10.2298/JSC1002185L; Original scientific paper

Binding of coenzymes to yeast alcohol dehydrogenase
VLADIMIR LESKOVAC, SVETLANA TRIVIĆ*, DRAGINJA PERIČIN, MIRA POPOVIĆ* and JULIJAN KANDRAČ**
Faculty of Technology, University of Novi Sad, Bulevar Cara Lazara 1, Novi Sad, Serbia

*Faculty of Science, University of Novi Sad, Novi Sad, Serbia

**Faculty of Agriculture, University of Novi Sad, Novi Sad, Serbia

(Received 26 May, revised 23 July 2009)

In this work, the binding of coenzymes to yeast alcohol dehydrogenase (EC 1.1.1.1) were investigated. The main criterions were the change in the standard free energies for individual reaction steps, the internal equilibrium constants and the overall changes in the reaction free energies. The calculations were performed for the wild type enzyme at pH 6–9 and for 15 different mutant type enzymes, with single or double point mutations, at pH 7.3. The abundance of theoretical and experimental data enabled the binding of coenzymes to enzyme to be assessed in depth.

Keywords: coenzyme binding; Gibbs free energy; yeast alcohol dehydrogenase.

J. Serb. Chem. Soc. 75 (2) 195–207 (2010)

J. Serb. Chem. Soc. 75 (2) 209–215 (2010)

J. Serb. Chem. Soc. 75 (2) 217–228 (2010)

UDC 547.415.584+542.913:57–188:543.42; JSCS–3954; doi: 10.2298/JSC1002217S; Original scientific paper

J. Serb. Chem. Soc. 75 (2) 229–242 (2010)

UDC 546.562’732’742’472+542.913+547.85+547.656+633.71–32; JSCS–3955; doi: 10.2298/JSC1002265K; Original scientific paper

Synthesis and structural studies of complexes of Cu, Co, Ni and Zn with isonicotinic acid hydrazide and isonicotinic acid (1-naphthylmethylene)hydrazide

ANGELA KRIZA, LUCICA VIORICA ABABEI*, NICOLETA CIOATERA**, ILEANA RĂU*** and NICOLAE STĂNICĂ****

University of Bucharest, Chemistry Faculty, 23, Dumbrava Rosie Street, Bucharest, Romania

*The House of Teaching Staff Giurgiu, 8, Nicholae Droc Barcian Street, Giurgiu, Romania

**University of Craiova, Chemistry Faculty, 107 I, Calea Bucuresti Street, Craiova, Romania

***Polytechnic Institute of Bucharest, Faculty of Applied Chemistry and Materials Science, 1, Polizu Steet, 011061 Bucharest, Romania

****Romanian Academy, Chemistry-Physics Institute, 202 Independence Avenue, 77208 Bucharest, Romania

(Received 15 April, revised 11 September 2009)

Eight new complexes of Cu(II), Co(II), Ni(II) and Zn(II) with isonicotinic acid hydrazide (isoniazid, (INH)) and isonicotinic acid (1-naphthylmethylene)hydrazide (INNMH), having the formula of the type [M(INH)(ac)₂] or [M(INNMH)(ac)₂] (M = Co(II), Ni(II) and Zn(II)) and [Cu(INH)(ac)₂]₂, [Cu(INNMH)(ac)₂]₂, were synthesized and characterized. All complexes were characterized based on elemental analyses, and IR, UV–VIS–NIR and EPR spectroscopy, as well as by thermal analysis and determination of their molar conductivity and magnetic moments. The structure of INNMH was established by single crystal X-ray analysis. In all complexes, both ligands were coordi¬nated to the metal via N and O. The complexes of Cu (II) were dimeric, with four bridges between acetate ions and Cu(II).

Keywords: isoniazid; isonicotinic acid (1-naphthylmethylene)hydrazide; template synthesis; X-ray study; transition metal complexes.

J. Serb. Chem. Soc. 75 (2) 243–248 (2010)

UDC 547.587.51–3+541.124.7+519.687+543.554; JSCS–3956, doi: 10.2298/JSC1002243S; Original scientific paper

Computer progrAMs for calculating pK_a: a comparative study for 3-(3-(2-nitrophenyl)prop-2-enoyl)-2H-1-benzopyran-2-one

SELMA ŠPIRTOVIĆ-HALILOVIĆ and DAVORKA ZAVRŠNIK

Department of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Sarajevo, Čekaluša 90, Sarajevo, Bosnia and Herzegovina

(Received 1 July, revised 20 August 2009)

Coumarin-based compounds containing a chalcone moiety exhibit antimicrobial activity. These substances are potential drugs and it is important to determine their pK_a values. However, they are almost insoluble in water. The dissociation constant was experimentally determined by potentiometric titration for 3-[3-(2-nitrophenyl)prop-2-enoyl]-2H-1-benzopyran-2-one because this compound shows good activity and solubility. A number of different computer progrAMs for the calculation of the dissociation constant of chemical compounds have been developed. The pK_a value of the target compound was calculated using three different computer progrAMs, i.e., the ACD/pKa, CSpK_aPredictor and ADME/ToxWEB progrAMs, which are based on different theoretical approaches. The analysis demonstrated good agreement between the experimentally observed pKa value of 3-[3-(2-nitrophenyl)prop-2-enoyl]-2H-1-benzopyran-2-one and the value calculated using the computer progrAM CSpKa.

Keywords: coumarin-based compounds; dissociation constant; computer progrAMs; potentiometric titration.

J. Serb. Chem. Soc. 75 (2) 249–258 (2010)

UDC 546.262.3–3+542.913:549.641:531.3+544.4; JSCS–3957; doi: 10.2298/JSC1002249W; Original scientific paper

A kinetic study of CO oxidation over the perovskite-like oxide LaSrNiO₄

KEJUN WANG and PING ZHONG

College of Chemistry and Life Sciences, Gannan Normal University, Ganzhou 341000, China

(Received 27 October 2008, revised 3 September 2009)

The effect of reactant/product concentrations, reaction temperature and contact time on CO oxidation was investigated, using the perovskite-like oxide LaSrNiO₄ as the catalyst. It was found that the reaction order of CO (reactant), as well as that of CO₂ (product), is negative, the reaction orders for CO and CO₂ being –0.32 and –0.51, respectively. However, the reaction order for O₂ is positive, having a value of 0.62. The negative reaction order of CO and CO₂ might be due to their competitive adsorption with O₂, preventing the proceeding of oxygen dissociation (the rate-determining step of the reaction). The activation energy (E_a) of the reaction was calculated to be 49.4 kJ mol^-1; this small activation energy suggests that LaSrNiO₄ is a potential candidate for the CO oxidation reaction. The optimum weight hourly space velocity (WHSV) of the reaction was found to be 0.6 g s cm^-3. The reaction conditions in the present case were (0.5–1 % CO + 0.5–2 % O₂ + 0–2 % CO₂), with He as the balance gas.

Keywords: CO oxidation; perovskite-like oxide; LaSrNiO₄; kinetics; mechanism.

J. Serb. Chem. Soc. 75 (2) 259–269 (2010)

UDC 538.913:667.284:532.14:66.081.2+535.33; JSCS–3958; doi: 10.2298/JSC1002259X; Original scientific paper

DFT Studies on the electronic structures of indoline dyes for dye-sensitized solar cells

JIE XU, GUIJIE LIANG, LUOXIN WANG, WEILIN XU, WEIGANG CUI, HUI ZHANG and ZENGCHANG LI

Key Lab of Green Processing &AMp; Functional Textiles of New Textile Materials, Ministry of Education, Wuhan University of Science &AMp; Engineering, 430073, Wuhan, Hubei, China

(Received 5 January, revised 3 September 2009)

A series of indoline dyes with promising efficiency for dye-sensitized solar cells (DSSCs) were studied using the density functional theory at the B3LYP/6-31g (d) level. The ground-state geometries, electronic structures and absorption spectra of these dyes are reported. The calculated results indicate that the energy levels of the HOMOs and LUMOs of these dyes are advantageous for electron injection. Their intense and broad absorption bands as well as favorable excited-state energy levels are key factor for their outstanding efficiencies in DSSCs.

Keywords: density functional theory; indoline dyes; dye-sensitized solar cells; electronic structures.

J. Serb. Chem. Soc. 75 (2) 271–282 (2010)

UDC 66.017–039.26.004.12:544.018.2; JSCS–3959; doi: 10.2298/JSC1002271L; Original scientific paper

Preparation and characterization of a new carbonaceous material for electrochemical systems

ZI JI LIN, XUE BU HU, YONG JIAN HUAI and ZHENG HUA DENG

Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, Chengdu, Sichuan 610041, and Graduate School of Chinese Academy of Sciences, Beijing 100039, P.R. China and Zhongke Laifang Power Science &AMp; Technology Co., Ltd., Chengdu, Sichuan 610041, P.R. China

(Received 19 February, revised 4 June 2009)

A new carbonaceous material was successfully prepared by the py-rolysis of scrap tire rubber at 600 °C under a nitrogen atmosphere. The physical characteristics of the prepared carbonaceous material were studied by scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). It was proved that the carbonaceous material had a disordered structure and spherical morphology with an average particle size about 100 nm. The prepared carbonaceous material was also used as electrodes in electrochemical systems to exAMine its electrochemical performances. It was demonstrated that it delivered a lithium insertion capacity of 658 mA h g^-1 during the first cycle with a coulombic efficiency of 68 %. Cyclic voltAMmogrAMs test results showed that a redox reaction occurred during the cycles. The chemical diffusion coefficient based on the impedance diagrAM was about 10^-10 cm² s^-1. The pyrolytic carbonaceous material derived from scrap tire rubber is therefore considered to be a potential anode material in lithium secondary batteries or capacitors. Furthermore, it is advantageous for environmental protection.

Keywords: pyrolytic carbon; scrap tire rubber; carbonaceous materials; electrochemical performance; coulombic efficiency; chemical diffusion coefficient.

J. Serb. Chem. Soc. 75 (2) 283–293 (2010)

UDC 547.42/.43+547.427.3:544–971; JSCS–3960; doi: 10.2298/JSC1002284R; Original scientific paper

Derived thermodynAMic properties of alcohol + cyclohexylAMine mixtures

IVONA R. RADOVIĆ, MIRJANA LJ. KIJEVČANIN, ALEKSANDAR Ž. TASIĆ, BOJAN D. DJORDJEVIĆ and SLOBODAN P. ŠERBANOVIĆ

Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, P. O. Box 35-03, 11120 Belgrade, Serbia

(Received 2 April, revised 19 August 2009)

Thermal expansion coefficients, α, excess thermal expansion coefficients, α^E, isothermal coefficients of pressure excess molar enthalpy, (∂H^E/∂p)_T,x, partial molar volumes, , partial molar volumes at infinite dilution, , partial excess molar volumes, , and partial excess molar volumes at infinite dilution, , were calculated using experimental densities and excess molar volumes, , data. All calculations are performed for the binary systems of cyclohexylAMine with 1-propanol or 1-butanol or 2-butanol or 2-methyl-2-propanol. The Redlich–Kister polynomial and the reduced excess molar volume approach were used in the evaluation of these properties. In addition, the aim of this investigation was to provide a set of various volumetric data in order to asses the influence of temperature, chain length and position of hydroxyl group in the alcohol molecule on the molecular interactions in the exAMined binary mixtures.

Keywords: binary mixtures; densities; volumetric properties; alcohols; cyclohexylAMine.

J. Serb. Chem. Soc. 75 (2) 295 (2010)

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