Indian Journal of Chemistry

Sect. A: Inorganic, Bio-inorganic, Physical, Theoretical & Analytical

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VOLUME 48A		NUMBER 7		July 2009
CONTENTS
911	Mo-amino acid complexes as analogs for molybdoenzyme: A DFT approach S Sabiah & B Viswanathan*		Molybdenum(VI)-amino acid complexes and their reduced species have been analyzed by DFT approach. All complexes show thermal stability in gaseous state whereas their solution state shows the possible solvent interactions. The atomic orbital contribution shows that Mo-d orbital contributes >50% to LUMO. As a preliminary approach for oxidation of xanthine substrate, the Mo(IV) and Mo(V) intermediates have been optimized with pyrimidine-4-ol, with oxygen atom insertion into a C-H bond. The optimized geometry and bond parameters are closely associated with the reported Mo-imidazole intermediate. It is proposed that the hydroxyl oxygen is being inserted in the C-H bond of the substrate to afford pyrimidin-2,4-diol as the product. Optimized Oh geometry of the Mo-Gly complex
921	A molecular structure descriptor derived from bond- disconnection: Application to quantitative structure property relationships Sagarika Sahoo, Sabita Patel*, Sukalyan Dash & B K Mishra*		Novel topological indices have been derived from a bond- disconnection protocol in a vertex weighted hydrogen depleted molecular graph. These indices are utilized in multiparametric models with other topological indices in quantitative structure property relationship for C-3 to C-9 alkanes.
930	Studies of partial molar volumes of alkylamine in non-electrolyte solvents. V – Alkylamines in toluene at 303.15 K S L Oswal* & S P Ijardar		Apparent molar volumes of some alkylamines, viz., n-propylamine, n-butylamine, di-n-propylamine, di-n-butylamine, triethylamine, tri-n-propylamine, and tri-n-butylamine in toluene at 303.15 K have been determined. The limiting partial molar volumes and limiting excess partial molar volumes have been interpreted in terms of solute-solvent interactions and structural effects of the molecules. The contribution of the specific interactions to the partial molar volumes of primary, secondary and tertiary amines in toluene have been analysed using Terasawa model, scaled particle theory and hard sphere theory. The ERAS model has also been applied to estimate the apparent molar volumes and excess apparent molar volumes of alkylamines in toluene solutions.
940	Selective amperometric sensing of hydrogen peroxide with Nafion/copper particulates chemically modified electrode Annamalai Senthil Kumar* & Sundaram Sornambikai		Nafion/copper particulates chemically modified glassy carbon electrode has been prepared by in situ electrochemical deposition. The electrode is successful for selective amperometric sensing of hydrogen peroxide at -0.2 V vs Ag/AgCl at physiological pH without interference from uric acid, ascorbic acid, catechol, cysteine, nitrite and nitrate. Two linear regions, 20-200 µM and 220-400 µM for H2O2 detection with slope and regression coefficient values of 33.2 nA/µM and 25.61 nA/µM and 0.9975 and 0.9999 respectively are obtained with 1.63 µM detection limit (S/N = 3). Application to real samples analysis is demonstrated for milk, urine and tea samples with appreciable recovery values.
Notes
946	Co-supported hexagonal mesoporous silicas for catalytic oxidation of 4-t-butyltoluene Weihua Yu*, Chunhui Zhou, Yongxian Fan, Caiying Lou, Dongshen Tong & Mei Fang		Co-supported hexagonal mesoporous silicas (Co 2, 4 and 8 wt. %) have been prepared by incipient wetness impregnation, using cobalt acetate tetrahydrate as metal precursors, and ethylene glycol as impregnation solvent. The divalent cobalt with a tetrahedral oxygen exists mainly in the calcined sample with loading Co ≤ 4 wt. %. Co3O4 particles have been detected in calcined 8 wt. % Co-HMS. The Co-HMS catalyst (8 wt. %) affords higher yield (17.6%) of 4-t-butylbenzaldehyde at 24.7% conversion in a reaction time of 5 h. The oxides of cobalt, especially Co3O4 particles, are responsible for the partial oxidation of 4-t-butyltoluene. The divalent cobalt ions in tetrahedral environment in the Co-HMS catalysts are unstable during the oxidation reaction.
951	Synthesis of TiO2-SiO2 powder and thin film photocatalysts by sol-gel method Radhiyah Abd Aziz & Iis Sopyan*		Binary metal oxide TiO2-SiO2 powder and thin film photocatalysts have been synthesized via sol-gel method using tetraethoxysilane and a titanium chelate compound as the silicon and titanium precursors respectively. XRD shows that the TiO2-SiO2 powder and thin film are totally in anatase structure after calcination at 500°C, which is also confirmed by TG-DTA. FESEM shows that the TiO2-SiO2 particles, in both the powder and film, are nano-sized spheres. The addition of low composition SiO2 to the TiO2 matrix suppresses the crystal growth of TiO2 and enhances the photocatalytic performance. The photocatalytic properties have been evaluated by studies on the degradation of gaseous acetaldehyde.
958	Kinetics and mechanism of palladium(II) catalysed oxidation of dimethyl sulfoxide by alkaline periodate B I Koli & S T Nandibewoor*		The kinetics of oxidation of dimethyl sulfoxide by periodate in the presence of palladium(II) catalyst in alkaline medium at 298 K is reported. The stoichiometry is [DMSO]:[IO4^-] = 1:1. The reaction exhibits first order dependence with respect to [IO4^-], an apparent less than unit order in [DMSO], [OH^-] and [palladium(II)] under the experimental conditions. A probable mechanism is proposed.
964	Liquid phase non-solvent selective oxidation of styrene using aqueous hydrogen peroxide with supported 12- tungstophosphoric acid Pankaj Sharma & Anjali Patel*		Non-solvent oxidative cleavage of styrene has been carried out over supported 12-tungstophosphoric acid with H2O2. The catalysts show very high conversion and selectivity towards benzaldehyde, an important product used as intermediate in many synthetic preparations. Further, the catalytic activity of calcinated catalysts has also been evaluated under optimized conditions. The present study shows the best catalysts to be PWA3/Z and PWA3/A with PWA3/A thermally more stable than PWA3/Z.
969	Announcement

Authors for correspondence are indicated by (*)

Indian Journal of Chemistry

Vol. 48A, July 2009, pp. 911-920

Mo-amino acid complexes as analogs for molybdoenzyme:
A DFT approach

S Sabiah & B Viswanathan*

National Centre for Catalysis Research, Indian Institute of Technology, Madras, Chennai 600 036, India

Email: bvnathan@iitm.ac.in

Received 17 April 2009; accepted 18 June 2009

A DFT investigation of hypothesized molybdenum(VI)-amino acid complexes has been considered as a model for xanthine oxidase. All these complexes have been optimized and analyzed by vibrational analysis. The complexes have been subjected to one electron reduction to produce anionic analogs. All complexes and reduced species are optimized in vacuum as well as in water and the associated free energy changes have been estimated. From these changes, the qualitative redox energy has been calculated by thermodynamic cycle which reveals that the complexes are expected to show similar redox behavior. This is also supported by a similar HOMO-LUMO energy gap. The population analysis shows that molybdenum d-orbital contributes >50% to LUMO, suggesting that the oxidation is metal-based in these systems. Also, 30% orbital contribution from sulfido center reveals the possible electronic delocalization through sulfur during oxidation of substrate. As a preliminary step for xanthine oxidation, pyrimidin-4-ol has been studied as a model substrate and the reduced sulfhydryl Mo(V) and sulfido Mo(IV)-substrate intermediates have been optimized with molybdenum in distorted square pyramidal geometry. The bond distances clearly show that Mo-S distance is longer in the sulfhydryl analogue than in the sulfide intermediate to support the involvement of hydride transfer in the catalytic cycle. The Mo-C2 (carbon flanked between both the nitrogens) distance of 3.237 Å and the C2-O distance of 1.28 Å are comparable with values reported for the Mo-imidazole intermediate. This study proposes that the hydroxyl oxygen is being inserted in the C-H bond of the substrate to afford pyrimidin-2,4-diol as the product.

Keywords: Theoretical chemistry, Density functional calculations, Metalloenzymes, Molybdoenzymes, Molybdenum, Xanthine oxidase, Mo-amino acid complexes

IPC Code: Int. Cl.⁸ C07C229/76; C07F11/00

Indian Journal of Chemistry

Vol. 48A, July 2009, pp. 921-929

A molecular structure descriptor derived from bond-disconnection: Application to quantitative structure property relationships

Sagarika Sahoo^a, Sabita Patel^b,*, Sukalyan Dash^c & B K Mishra^a, *

^aSchool of Chemistry, Centre of Studies in Surface Science and Technology, Sambalpur University,

Jyoti Vihar, Burla 768 019, India

^bDepartment of Chemistry, National Institute of Technology, Rourkela 769 008, India

^cDepartment of Chemistry, University College of Engineering, Burla 768 018, India

Email: bijaym@hotmail.com

Received 30 April 2009 ; revised and accepted 27 May 2009

A set of novel molecular structure descriptors, viz., vertex weighted walk parameter, has been derived by using a bond-disconnection protocol in hydrogen depleted vertex weighted molecular graph. The parameters are correlated with other topological indices by constructing the correlation matrix and by correlating with the principal components of these indices. The applicability of these parameters in quantitative structure property relationships has been investigated for boiling points, molar volume at 20 ºC, molar refractions at 20 ºC, heats of vaporization at 25 ºC, critical temperature and surface tension at 20 ºC. Both the single parametric model and multiparametric model have been used for the QSPR studies. Successive exclusion of variables technique has been used to optimize the multiparametric models. The high collinearity of the observed and predicted properties reveals the applicability of the proposed parameters.

Keywords: Theoretical chemistry, Graph theory, Molecular descriptors, Topological indices, Connectivity parameters, Vertex weighted walk parameter, Structure-activity relationships

Indian Journal of Chemistry

Vol. 48A, July 2009, pp. 930-939

Studies of partial molar volumes of alkylamines in non-electrolyte solvents. V – Alkylamines in toluene at 303.15 K

S L Oswal^a, * & S P Ijardar^b

^aBiochemistry Division, R&D Span Diagnostic Limited, 173-B, New Industrial Estate, Udhna, Surat 394 210, India

Email: oswalsl@yahoo.co.uk

^bDepartment of Chemistry, SV National Institute of Technology, Surat 395 007, India

Received 30 April 2009 ; revised and accepted 23 June 2009

Apparent molar volumes, , of n-propylamine, n-butylamine, di-n-propylamine, di-n-butylamine, triethylamine, tri-n-propylamine, and tri-n-butylamine in toluene at 303.15 K have been determined with high precision vibrating tube Anton Paar densimeter. The limiting partial molar volumes and limiting excess partial molar volumes are analysed and interpreted in terms of solute-solvent interactions and structural effects of the molecules. An attempt has been made to find a measure of the contribution of the specific interactions to the partial molar volumes of primary, secondary and tertiary amines in toluene using Terasawa model, scaled particle theory and hard sphere theory. The ERAS model has also been applied to estimate the apparent molar volumes and excess apparent molar volumes of alkylamines in toluene solutions.

Keywords: Solution chemistry, Thermodynamics, Hard sphere theory, Scaled particle theory, ERAS model, Partial molar volumes, Alkylamines, Toluene

Indian Journal of Chemistry

Vol. 48A, July 2009, pp. 940-945

Selective amperometric sensing of hydrogen peroxide with Nafion/copper particulates chemically modified electrode

Annamalai Senthil Kumar* & Sundaram Sornambikai

Department of Chemistry, Vellore Institute of Technology University, Vellore 632 014, India

Email: askumarchem@yahoo.com

Received 16 April 2009 ; revised and accepted 19 June 2009

Nafion/copper particulates chemically modified glassy carbon electrode has been prepared by in situ electrochemical deposition. The electrode is found to to be successful for selective amperometric sensing of hydrogen peroxide at -0.2 V vs Ag/AgCl at physiological pH without interference from uric acid, ascorbic acid, catechol, cysteine, nitrite and nitrate. Two linear regions, 20-200 µM and 220-400 µM, for H₂O₂ detection with the slope and regression coefficient values of 33.2 nA/µM and 25.61 nA/µM and 0.9975 and 0.9999 respectively are obtained with 1.63 µM detection limit (S/N = 3). Application to real samples analysis is demonstrated for milk, urine and tea samples with appreciable recovery values

Keywords: Electrochemistry, Analytical chemistry, Electrocatalysis, Glassy carbon electrodes, Modified electrodes, Copper, Hydrogen peroxide

IPC Code: Int. Cl.⁸ G01N27/00; H01M4/00

Indian Journal of Chemistry

Vol. 48A, July 2009, pp. 946-950

Co-supported hexagonal mesoporous silicas for catalytic oxidation
of 4-t-butyltoluene

Weihua Yu ^a, *, Chunhui Zhou^a, Yongxian Fan^a, Caiying Lou^b, Dongshen Tong^a & Mei Fang^a

^aCollege of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310014, China

Email: ywh@zjut.edu.cn

^bMaterials-Textile College, Zhejiang Sci-Tech University, Hangzho 310018, China

Recevied 10 December 2008 ; revised and accepted 14 June 2009

Co-supported hexagonal mesoporous silicas (Co 2, 4 and 8 wt. %) have been prepared by incipient wetness impregnation, using cobalt acetate tetrahydrate as metal precursors and ethylene glycol as impregnation solvent. The materials have been characterized by XRD, N₂ adsorption-desorption isotherms and diffuse reflectance UV-vis spectroscopy. The divalent cobalt with a tetrahedral oxygen exists mainly in the calcined sample with loading Co ≤ 4 wt. %. The Co₃O₄ particles have been detected in calcined 8 wt. % Co-HMS. The catalytic properties have been tested for oxidation of 4-t-butyltoluene with dioxygen in liquid phase under mild conditions. Co-HMS catalyst (8 wt. %) affords higher yield (17.6%) of 4-t-butylbenzaldehyde at 24.7% conversion in a reaction time of 5 h. The oxides of cobalt, especially Co₃O₄ particles, are responsible for the partial oxidation of 4-t-butyltoluene. The divalent cobalt ions in tetrahedral environment in the Co-HMS catalysts are unstable during the oxidation reaction.

Keywords: Catalysts, Oxidations, Mesoporous materials, Silica, Cobalt, Impregnation method

IPC Code: Int. Cl.⁸ B01J21/08; B01J37/02; C07B33/00

Indian Journal of Chemistry

Vol. 48A, July 2009, pp. 951-957

Synthesis of TiO₂-SiO₂ powder and thin film photocatalysts
by sol-gel method

Radhiyah Abd Aziz & Iis Sopyan*

Department of Manufacturing and Materials Engineering, Faculty of Engineering,

International Islamic University Malaysia (IIUM), PO Box 10, 50728 Kuala Lumpur, Malaysia

Email: sopyan@iiu.edu.my

Received 4 February 2009 ; revised and accepted 19 June 2009

Binary metal oxide TiO₂-SiO₂ powder and thin film photocatalysts have been synthesized via sol-gel method using tetraethoxysilane and a titanium chelate compound as the silicon and titanium precursors respectively. The physico-chemical properties of the TiO₂-SiO₂ powder and thin film are characterized using TG-DTA, FTIR, XRD, FESEM, and UV-vis data. XRD analysis shows that the TiO₂-SiO₂ powder and thin film obtained are in fully anatase structure after calcination at 500°C, which is also confirmed by TG-DTA analysis. The FESEM picture shows that the TiO₂-SiO₂ particles in both powder and film are nano-sized spheres. The addition of low composition SiO₂ to the TiO₂ matrix suppresses the crystal growth of TiO₂ and enhances the photocatalytic performance. The photocatalytic properties have been evaluated by studies on the degradation of gaseous acetaldehyde.

Keywords: Catalysts, Photocatalysts, Sol-gel processes, Oxides, Binary oxides, Titania, Silica, Thin films

IPC Code: Int. Cl.⁸ B01J21/00; B01J37/00

Indian Journal of Chemistry

Vol. 48A, July 2009, pp. 958-963

Kinetics and mechanism of palladium(II) catalysed oxidation of
dimethyl sulfoxide by alkaline periodate

B I Koli & S T Nandibewoor*

P G Department of Chemistry, Karnatak University, Dharwad 580 003, India

Email: stnandibewoor@yahoo.com

Received 26 December 2008 ; revised and accepted 10 June 2009

The kinetics of oxidation of dimethyl sulfoxide by periodate, has been carried out in the presence of palladium(II) catalyst in alkaline medium at 298 K. The stoichiometry is [DMSO]: [IO₄^-] = 1:1. The reaction exhibits first order dependence with respect to [IO₄^-], an apparent less than unit order in [DMSO], [OH^-] and [palladium(II)] under the experimental conditions. A probable mechanism is proposed. The reaction constants involved in the different steps of the mechanism have been calculated. The activation parameters with respect to slow step of the mechanism have been computed and discussed.

Keywords: Kinetics, Reaction mechanisms, Oxidations, Periodate oxidation

IPC Code: Int. Cl.⁸ C07B33/00

Indian Journal of Chemistry

Vol. 48A, July 2009, pp. 964-968

Liquid phase non-solvent selective oxidation of styrene using
aqueous hydrogen peroxide with supported 12-tungstophosphoric acid

Pankaj Sharma & Anjali Patel*

Chemistry Department, Faculty of Science, The MS University of Baroda, Vadodara, India

Email: aupatel_chem@yahoo.com

Received 31 December 2008 ; revised and accepted 23 June 2009

Non-solvent oxidative cleavage of styrene has been carried out over supported 12-tungstophosphoric acid with H₂O₂. The present catalysts show very high conversion and selectivity towards benzaldehyde, an important product used as intermediate in many synthetic preparations. Further, the catalytic activity of calcinated catalysts has also been evaluated under optimized conditions. The present study shows the best catalysts to be PWA₃/Z and PWA₃/A with PWA₃/A thermally more stable than PWA₃/Z.

Keywords: Catalysts, Oxidations, Supported catalysts, Non-solvent oxidations, Hydrocarbons, Styrene, Tungstophosphoric acid

IPC Code: Int. Cl.⁸ B01J27/186; C07B31/00

Indian Journal of Chemistry

Vol. 48A, July 2009, p. 969

Announcement

Second International Conference on
Application of Radiotracers in Chemical, Environmental and Biological Sciences
(ARCEBS-10)
7-13 February, 2010

The Second International Conference on Application of Radiotracers in Chemical, Environmental and Biological Sciences (ARCEBS-10) is being held on 7-13 February 2010 at the Saha Institute of Nuclear Physics, Kolkata, India. The ARCEBS is a perfect blend of physics, chemistry, biology, medicine and other interdisciplinary researches using radioisotopes. The scope of the conference includes application of radiotracers in accelerator mass spectrometry, alternative solvents, bioaccumulation studies, biomonitoring, chemistry, ecology, environment, green chemistry, industry, migration studies, natural radioactivity, nuclear medicine, radioactive ion beam, radioisotope production, super heavy elements, etc.

The last date of submitting the abstract is September 15, 2009.

Further details may be obtained from Prof Susanta Lahiri, Convenor ARCEBS 10, Chemical Sciences Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700 064, India; Email: arcebs.2010@saha.ac.in/ arceba2010@gmail.com; Tel: 0091-33-23375345-48, Extn 1118; Fax: 0091-33-23374637; website: http://www.saha.ac.in/cs/arcebs.2010.