Indian Journal of Chemistry

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

 

VOLUME 41A

NUMBER 10

October 2002

CONTENTS

Papers

 

1995

 

A localized molecular orbital study of the structure and bonding of ozone

 

 

 

Dulal C Ghosh* & Arindam Chakraborty

 

 

 

The studies cover a large number of conformations generated theoretically over the wide range of apical angles between angular to linear shapes. The results demonstrate that, similar to the bonding in diborane, there are two equivalent three-centered bonds in ozone embracing three oxygen atoms in all the conformations.

 

 

2008

 

Investigation of microstructure of glycidyl methacrylate/methyl acrylate copolymers by 1D and 2D-NMR spectroscopy.

 

 

 

A S Brar* & Anil Yadav

 

 

 

The copolymers of glycidyl methacrylate/methyl acrylate have been synthesized by solution polymerisation using benzene as solvent and benzoylperoxide as an initiator. The Distortionless Enhancement by Polarization Transfer, 13C-1H heteronuclear single quantum coherence and Total Correlation Spectroscopy have been used for the complete spectral assignment of 13C and 1H-NMR spectra.

 

2017

 

Volumetric properties of binary mixtures of some n-alkoxyethanols with 2-pyrrolidinone and N-methyl-2-pyrrolidinone at 298.15 K

 

 

 

 

 

Amalendu Pal*, Anil Kumar & Harsh Kumar

 

 

 

The excess molar volumes for binary liquid mixtures of
n-alkoxyethanol + 2-pyrrolidinone or N-methyl-2-pyrrolidinone have been measured with a continuous dilution dilatometer. In all mixtures the excess molar volumes are negative across the entire composition range. In each case the excess molar volumes decrease as the alkyl chain length of the alkoxyethanol increases while it increases from 2-pyrrolidinone to N-methyl-2-pyrroli-dinone.

 

 

2025

 

Voltammetric studies of an oxazolone derivative of cefaclor in aqueous buffers

 

 

 

 

 

 

Bhim Bali Prasad*, Sandeep Gupta &

Shouri Banerjee

 

 

 

 

2032

 

A study on viscosity B-coefficient of some mineral salts in binary aqueous solutions of urea at various temperatures

 

 

 

 

M L Parmar*, D K Dhiman & R C Thakur

 

 

 

Relative viscosities of some mineral salts viz; sulphates of sodium, potassium/ammonium and magnesium, at different concentrations have been determined in binary aqueous solutions of urea at different temperatures. The sulphates of ammonium and magnesium behave as structure breakers whereas sodium and potassium sulphate act as structure makers in the present system.

 

 

2039

 
A study of activation parameters for viscous flow process of some tetraalkylammonium salts in binary mixtures of N, N–dimethyl-formamide and ethyl methyl ketone

 

 

 

 

Baljeet S Patial, S Chauhan, M S Chauhan* &

V K Syal

 

 

 

Viscosities and densities of tetrabutylammoniumtetra-phenylammonium boride tetrabutylammonium bromide, tetrapentylammonium bromide, tetrahexylammonium iodide, sodium tetraphenyl boride and sodium iodide in ethyl methyl ketone (EMK), N, N-dimethyl formamide (DMF) and EMK+ DMF solvent mixtures have been reported. The activation parameters have been examined as a function of solvent composition to interpret the solution behaviour of these salts in EMK-DMF mixtures.

 

2046

 

Anchoring mercapto-triazoles on dicarbonyl backbone to assemble novel binucleating, acyclic SNONS compartmental ligands

 

 

 

 

 

 

 

 

Anil D Naik, Satish M, Annigeri, Umesh B, Gangadharmath, Vidyanand K Revankar*, Vinayak B Mahale & Vijay Kumar Reddy

 

 

 

 

2054

 

Silyl-nitrogen compounds: Part XIII—Reactions of metal halides with silylated tosylhydrazines

 

 

 

 

 

 

 

 

 

 

 

S K Vasisht* , P Venugopalan , Jyoti Kataria &

Anuradha Sharma

 

 

2060

 

 

Reactivity of [{(h6-p-cymene)RuCl(m-Cl)}2] towards some N-heterocyclics and tertiary phosphines

 

 

 

 

 

 

 

 

 

M Sarangapani & V Ravinder*

 

 

 

 

 

Notes

 

2065

 

Prediction of 13C nuclear magnetic resonance chemical shifts (å13Cn) in alkanes
and cycloalkanes

 

 

P V Khadikar*, A V Bajaj & D Mandloi

 

 

A topological method is described for prediction of 13C NMR chemical shifts of alkanes and cycloalkanes using PI index. Some good results are obtained when the cycloalkanes are classified into low, middle and high ring-size.

2068

 

 

Preparation and unusual absorption properties of a ferrocene ended 2,6-bis-stilbazonium salt

 

 

 

 

 

 

 

 

Saumitra Sengupta* & Subir Kumar

Sadhukhan

 

 

 

 

 

2071

 

Synthesis and characterization of some novel 4-formyl pyrazolylthiazoles of potential medicinal interest using Vilsmeier-Haack reaction

 

 

 

 

 

 

Pawan K Sharma*, Karan Singh,

S N Dhawan & S P Singh

 

 

 

 

2076

 

Synthesis and characterization of dinuclear ruthenium(II) and ruthenium(III) acetyl-acetonato complexes with dianion of 2,5-dihydroxy-1,4-benzoquinone as bridging ligand

 

 

 

Akhilesh K Gupta*, Anupama Gupta &

Anuradha Choudhury

 

 

 

Synthesis of [{(acac)2Ru}2(m-L)] and [{(bipy)(acac)Ru}2(m-L)] has been achieved by the reaction of dipotassium salt of 2,5-dihydroxy-1,4-benzoquinone) with two equivalents of cis-[RuIII(acac)2(CH3CN)2] or [RuIIBr(acac)(bipy)].

 

2079

 

Silyl-nitrogen compounds: Part XIV— Reactivity of tetrasila-phospha-tetrazene towards some group(IV) derivatives

 

 

 

 

 

S.K. Vasisht*, B N Anand & Km. Usha Johal

 

 

 

 

 

2083

 

Synthesis and characterization of mixed ligand complexes of Cu(II), Ni(II) and Co(II) with cytidine and amino acids

 

 

 

 

 

 

 

 

 

P Rabindra Reddy* & A Mohan Reddy

 

 

 

 

2088

 

Ternary complexes of nickel(II) involving
6-aminopenicillanic acid and some potentially bidentate or tridentate ligands

 

 

 

 

M Sivasankaran Nair* & M A Neelakantan*

 

 

 

 

 

2092

 

 

 

 

Synthesis, characterization, thermal decomposition and kinetic parameters of Ni(II) and Cu(II) terephthalate-8Hq complexes

 

 

 

A P Mishra, V K Tiwari & R Singhai*

 

 

 

Ni(II)-8Hq terephthalate and Cu(II)-8Hq terephthalate complexes have been synthesised and characterized by varoius analytical and spectroscopic techniques.

2096

 

 

Photooxidation of substituted purines in presence of peroxydisulphate in aqueous solution

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Midudhula Sudha Swaraga &

Mundra Adinarayana*

 

 

 

 

 

Authors for correspondence are indicated by (*)

 

 

 

 

Indian Journal of Chemistry

Vol. 41A, October 2002, pp.1995-2007

 

A localized molecular orbital study of the structure and bonding of ozone

Dulal C Ghosh* & Arindam Chakraborty

The localized molecular orbital theory and energy partitioning formalism have been invoked to study the structure and bonding in ozone molecule. The range of investigation covers a large number of conformations generated theoretically over the wide range of apical angles between angular (C2v) to linear (D¥h) shapes. The results demonstrate that, similar to the bonding in diborane, there are two equivalent three-centered bonds in ozone embracing three oxygen atoms in all the conformations. The possibility of a triangular structure of ozone is ruled out because the computed localized molecular orbitals demonstrate that there is no bonding between the terminal oxygen atoms and the decomposed energy components show that the interaction between terminal oxygen atoms is strongly repulsive. Charge density distribution is asymmetric in the homonuclear molecule and its dipole moment is an algebraic sum of bond moment and lone pair moment and lone pair on the apical oxygen atom contributes significantly to the dipole moment. It is demonstrated that any attempt of calculating the apical angle from the experimentally determined dipole moment would be erroneous and misleading. Variation of dipole moment as a function of angular to linear reorganization of molecular shape is correlated in terms of computed quantum mechanical hybridization of the lone pair on the apical oxygen atom. The barrier to inversion of ozone through the linear (D¥h) transition state originates from a subtle interplay of one- and two- center energy components over the entire skeleton of the molecule.

 

Indian Journal of Chemistry

Vol. 41A, October 2002, pp.2008-2016

 

Investigation of microstructure of glycidyl methacrylate/methyl acrylate copolymers by 1D and 2D- NMR spectroscopy

 

A S Brar* & Anil Yadav

 

The copolymers of glycidyl methacrylate/methyl acrylate (G/M) have been synthesized by solution polymerisation using benzene as solvent and benzoylperoxide as an initiator. The 1H-NMR spectroscopy has been used to determine the copolymer compositions. The comonomer reactivity ratios have been determined by Kelen- Tudos (KT) and non-linear least squares error in variable method (EVM) and are found to be rG = 4.03 ± 0.7, rM = 0.45 ± 0.07 and rG=4.6, rM = 0.49, respectively. The Distortionless Enhancement by Polarization Transfer (DEPT), 13C-1H heteronuclear single quantum coherence (HSQC) and Total Correlation Spectroscopy (TOCSY) were used for the complete spectral assignment of 13C and 1H-NMR spectra.

Indian Journal of Chemistry

Vol. 41A, October 2002, pp.2017-2024

 

 

Volumetric properties of binary mixtures of some n-alkoxyethanols with2-pyrrolidinone and N-methyl-2-pyrrolidinone at 298.15 K

Amalendu Pal*, Anil Kumar & Harsh Kumar

 

The excess molar volumes (VE) for binary liquid mixtures of (n-alkoxyethanol + 2-pyrrolidinone or N-methyl-2-pyrrolidinone) have been measured with a continuous dilution dilatometer at 298.15 K and atmospheric pressure as a function of composition. The alkoxyethanols are 2-methoxyethanol (CH3OCH2CH2OH), 2-ethoxyethanol (C2H5OCH2CH2OH), and 2-butoxyethanol (C4H9OCH2CH2OH). In all mixtures the excess molar volumes are negative across the entire composition range. In each case the excess molar volumes decrease as the alkyl chain length of the alkoxyethanol increases while it increases from 2-pyrrolidinone to N-methyl-2-pyrrolidinone. The results have been used to estimate the excess partial molar volumes  of the components. The change of VE and  with composition and the number of alkyl chain-length in the alkoxyethanol molecule is discussed with a view to understand some of the molecular interactions present in alkoxyethanol-cyclic amide mixtures.

Indian Journal of Chemistry

Vol. 41A, October 2002, pp.2025-2031

 

Voltammetric studies of an oxazolone derivative of cefaclor in aqueous buffers

 

Bhim Bali Prasad*, Sandeep Gupta & Shouri Banerjee

 

Electrochemical properties of cefaclor at a mercury electrode in aqueous solution of varying pH have been studied through tast, pulse (normal and differential), and cyclic voltammetric techniques. For this, the electroinactive cefaclor is transformed into electroactive penicillenate analogue ‘oxazolone derivative’ under strong acidic hydrolysis condition. The derived oxazolone system underwent two-steps irreversible reductions involving proton-participations (2e-, H+; 4e-, 4H+) when voltammograms scanned  cathodically. However, in cyclic voltammetry, a typical wave due to sulphhydryl group oxidation is noticed on scan reversal in anodic direction. The results have been discussed by taking into account the implications of reactant and product adsorptions onto electrode surface during the course of reductions.

 

Indian Journal of Chemistry

Vol. 41A, October 2002, pp.2032-2038

 

 

A study on viscosity B–coefficient of some mineral salts in binary aqueous solutions of urea at various temperatures

 

 

M L Parmar*, D K Dhiman & R C Thakur

 

 

Relative viscosities of some mineral salts viz; sodium sulphate, potassium sulphate, ammonium sulphate and magnesium sulphate, at different concentrations have been determined in binary aqueous solutions of urea (mole-fractions of urea, Xurea = 0.010, 0.025, 0.040, 0.055 and 0.070) at 308.15K and in Xurea = 0.025 at different temperatures.  The data have been evaluated using Jones-Dole equation and the obtained parameters are interpreted in terms of ion-ion and ion-solvent interactions.  The activation parameters of viscous flow have been obtained which throw light on the mechanism of viscous flow.  Ammonium sulphate and magnesium sulphate behave as structure breakers whereas sodium sulphate and potassium sulphate act as structure makers/promoters in the present system.

 

Indian Journal of Chemistry

Vol. 41A, October 2002, pp.2039-2045

A study of activation parameters for viscous flow process of some tetraalkylammonium salts in binary mixtures of N, N–dimethylformamide and ethyl methyl ketone

 

Baljeet S Patial, S Chauhan, M S Chauhan* & V K Syal

 

     Viscosities and densities of tetrabutylammoniumtetraphenylammonium boride (Bu4NBPh4), tetrabutylammonium bromide (Bu4NBr), tetrapentylammonium bromide (Pen4NBr), tetrahexylammonium iodide (Hex4NI), sodium tetraphenyl boride (NaBPh4) and sodium iodide (NaI) in ethyl methyl ketone (EMK), N, N-dimethyl formamide (DMF) and EMK+DMF solvent mixtures containing 0, 20, 40, 60, 80 and 100 mol % of EMK in the concentration range (0.02 – 0.1) mol dm-3 at 25, 35, and 45oC have been reported. The viscosity data have been analyzed in terms of A- and B- viscosity coefficients of the Jones–Dole equation. Both A- and B–coefficients have been found to be positive over the entire solvent composition range at all temperatures. The B-coefficients have been resolved into B± ionic coefficients using Bu4NBPh4 assumptions. The B± values of tetraalkylammonium ions are found to be positive. Partial molal volumes (Vo2) have also been calculated which have been used along with B- values to calculate activation parameters for viscous flow process of electrolytic solutions. The activation parameters have been examined as a function of solvent composition to interpret the solution behaviour of these tetraalkylammonium salts in EMK-DMF mixtures.

 

Indian Journal of Chemistry

Vol. 41A, October 2002, pp.2046-2053

 

Anchoring mercapto-triazoles on dicarbonyl backbone to assemble novel binucleating, acyclic SNONS compartmental ligands

Anil D. Naik, Satish M, Annigeri, Umesh B, Gangadharmath, Vidyanand K Revankar*,
Vinayak B Mahale & Vijay Kumar Reddy

 

A series of homobinuclear CoII, NiII, CuII and ZnII complexes of the form [M2(Cl)xL](H2O)y have been synthesized, where L is the deprotonated form of a new acyclic ligand resulting from the Schiff base condensation of one mol of 2,6-diformyl-p-cresol and two moles of triazoles (4-amino-3-methyl-1,2,4-triazole-5-thione; 3-methylsulphydryl-4-amino-5-mercapto 1,2,4-triazole and 3,5 dimercapto-4-amino-1,2,4-triazole) and characterized by spectral, magnetic, thermal and redox properties. Cryomagnetic investigations (79-296 K) reveal a strong antiferromagnetic spin-exchange between the copper (II) ions (J based on H = -2 J Ŝ1. Ŝ2.is 260 cm-1). The copper complex (CuII-CuII) oxidizes at a relatively low potential (+0.55 V vs saturated calomel electrode) leading to the formation of the corresponding CuIII-CuIII complex. The EPR spectra of the copper complexes indicate an isotropic or axially elongated or exchange coupled local molecular environment around the metal ion. All compounds including the ligands are antimicrobially active.

Indian Journal of Chemistry

Vol. 41A, October 2002, pp.2054-2059

 

Silyl-nitrogen compounds: Part XIII—Reactions of metal halides
with silylated tosylhydrazines

 

S K Vasisht*, P Venugopalan, Jyoti Kataria & Anuradha Sharma

 

 

Bis(trimethylsilyl)tosylhydrazine (Me3Si)2TsN2H reacts with ECln (E=Al,Sn,Sb or Ti) to liberate Me3SiCl and in the process form tosylhydrazides, ECln-1(Me3Si)TsN2H. These compounds decompose on heating in vacuo to form a variety of azane derivatives with the loss of volatile products like Me3SiCl, HCl or SbCl3. Ditosyltetrazene intermediate decomposes into ditosylhydrazine whose structure is determined by X-ray diffraction.

 

Indian Journal of Chemistry

Vol. 41A, October 2002, pp.2060-2064

 

Reactivity of [{(h6-p-cymene)RuCl(m-Cl)}2] towards some N-heterocyclics and tertiary phosphines

Sarangapani M & Ravinder V*

Reactions of [{(h6-p-cymene)RuCl(m-Cl)}2] with anthranilic acid (aa), pyrazole, 3-methylpyrazole, 3,5-dimethylpyrazole, indazole, imidazole, benzimida-zole and tertiary phosphines have been carried out to give complexes with the formula [(h6-p-cymene)Ru(aa)Cl], [(h6-p-cymene)Ru(aa)L] and [(h6-p-cymene)-Ru(aa)L¢]BF4. The anthranilic acid behaves in a chelating bidentate N,O-bonded mode. Further, chloride substitution takes place with azole derivatives and tertiary phosphines to produce the neutral and cationic complexes, respectively. The complexes have been characterised on the basis of elemental analyses, conductance measurements, IR, 1H, 13C and 31P-NMR and electronic spectral data and probable structures have been proposed. Redox behavior of these complexes was also studied by cyclic voltammograms. An irreversible single reduction wave for Ru(II) to Ru(0) ranging from –0.5 - –1.4 volts has been observed, which indicates a single step two electron process.

Indian Journal of Chemistry

Vol. 41A, October 2002, pp.2065-2067

 

Prediction of 13C nuclear magnetic resonance chemical shifts (å13Cn) in alkanes and cycloalkanes

 

P V Khadikar*, A V Bajaj  & D Mandloi

 

 

A topological method is described for prediction of 13C NMR chemical shifts (å13Cn) of alkanes and cycloalkanes using recently introduced PI (Padmakar- Ivan) index and to establish relative potential of PI index compared to Wiener (W) and Szeged (Sz) indices. Regression analysis of the data shows that in the case of alkanes the PI index gives somewhat better results than W, whereas in the case of cycloalkanes neither PI nor W nor Sz are applicable. However, excellent results are obtained when the cycloalkanes are classified into low, middle, and high ring-size.

 

Indian Journal of Chemistry

Vol. 41A, October 2002, pp.2068-2070

 

Preparation and unusual absorptionproperties of a ferrocene ended 2,6-bis-stilbazonium salt

Saumitra Sengupta* & Subir Kumar Sadhukhan

A 2,6-bis(ferrocenylvinyl)pyridinium salt, despite having a meta-orientation of the two ferrocenylvinyl groups, shows a significant bathochromic shift compared to a 2-(ferrocenylvinyl)-pyridinium salt. This unusual phenomenon is explained through participation of a cationic extended conjugated pathway present in the resonance forms of the former.

Indian Journal of Chemistry

Vol. 41A, October 2002, pp.2071-2075

 

Synthesis and characterization of some novel 4-formyl pyrazolylthiazoles of potential medicinal interest using Vilsmeier-Haack reaction

Pawan K Sharma*, Karan Singh, S N Dhawan & S P Singh

 

Two series of 4-formyl-1,3-disubstituted pyrazoles namely 2-[3-(2,4-difluorophenyl)-4-formylpyrazol-1-yl]-6-substituted benzothiazoles (3) and 2-[3-(2,4-difluorophenyl)-4-formylpyrazol-1-yl]-4-arylthiazoles (7) have been synthesized for evaluation of their antifungal activity through Vilsmeier-Haack reaction on hydrazones (2,6) of 2,4-difluoroacetophenone with 2-hydrazino-6-substituted benzothiazoles (2) and 2-hydrazino-4-phenyl/substituted phenylthiazoles (6). None of the compounds exhibit any significant antifungal activity.

 

Indian Journal of Chemistry

Vol. 41A, October 2002, pp.2076-2078

 

Synthesis and characterization of dinuclear ruthenium(II) and ruthenium(III) acetyl-acetonato complexes with dianion of 2,5-dihydroxy-1,4-benzoquinone as bridging ligand

 

 

Akhilesh K Gupta*, Anupama Gupta & Anuradha Choudhury

 

 

Synthesis of [{(acac)2Ru}2(m-L)] and [{(bipy)(acac)Ru}2(m-L)] (where acac=acetylacetonato, bipy=2,2¢-bipyridine) has been achieved by the reaction of K2L (where K2L=dipotassium salt of 2,5-dihydroxy-1,4-benzoquinone) with two equivalents of cis-[RuIII(acac)2(CH3CN)2] or [RuIIBr(acac)(bipy)]. The complexes have been characterized on the basis of elemental analyses, magnetic susceptibility and conductivity data, IR, UV-visible and 1H NMR spectral data and cyclic voltammetric studies.

 

Indian Journal of Chemistry

Vol. 41A, October 2002, pp.2079-2082

 

Silyl-nitrogen compounds: Part XIV—Reactivity of tetrasila-
phospha-tetrazene towards some group (IV) derivatives

 

S K Vasisht*, B N Anand & Km Usha Johal

 

Tetrasila-2-phospha-1-tetrazene (Ms3Si)2N-N(SiMe3)-P=NSiMe3 is oxidized by CBr4 into [tris(trimethylsilyl)hydrazino] [(trimethylsilyl)imino] (dibromo) phosphorane which lose Me3SiBr, on heating in vacuum, to form [bis (trimethylsilyl)-hydrazino][trimethylsilylimino] (bromo)phosphorane. Carbon disulphide forms a [1+2]-cycloadduct, which decomposes at 60°C/10-3 torr back into its reactants. Dichlorodimethylsilane and tetrachlorosilane behave similarly to form diaza-phospha-sila-cyclobutane derivatives, whereas, the latter also form a spirobicyclic derivative. All these compounds have been characterised.

Indian Journal of Chemistry

Vol. 41A, October 2002, pp.2083-2087

 

Synthesis and characterization of mixed ligand complexes of Cu(II), Ni(II) and Co(II) with cytidine and amino acids

 

P Rabindra Reddy* & A Mohan Reddy

 

 

The mixed ligand complexes of Cu(II), Ni(II) and Co(II) with cytidine and amino acids, l-alanine, l-phenylalanine and l-tryptophan have been synthesized and characterized by elemental analysis, conductivity, Infrared spectra, electronic spectral data and magnetic susceptibility measurements. In these complexes, the nucleoside acts as a monodentate ligand involving only N(3) in metal coordination whereas the amino acids acts as bidentate ligands coordinating through carboxylate oxygen and amino nitrogen. A distorted octahedral geometry for Cu(II), and octahedral geometries for both Ni(II) and Co(II) was proposed.

 

Indian Journal of Chemistry

Vol. 41A, October 2002, pp.2088-2091

Ternary complexes of nickel(II) involving 6-aminopenicillanic acid and some potentially bidentate or tridentate ligands

M Sivasankaran Nair* & M A Neelakantan

Multiple equilibrium studies by pH-metric and visible spectral measurements in the ternary nickel(II) complexes with 6-amino-penicillanic acid (6apa) as ligand A and diamines [1,2-diaminopropane(dp), and 1,3-diaminopropane(tp)] and diamino-carboxylic acids [ dl-2,3-diaminopropionic acid(dapa), dl-2,4-diaminobutyric acid(daba) and dl-2,5-diaminovaleric acid(dava)] as ligands B show the presence of NiABH2, NiABH or NiAB ternary complex species. The ligand, 6apa binds the metal ion via 6 amino and 7 carbonyl oxygen atoms in both the NiABH and NiAB species, and the binding of ligand B in NiAB complexes is exactly similar to their binding in the respective binary species. The results indicate the site of protonation in the NiABH species to be with the terminal amino group of the ligand B. In the NiABH2 complexes, one proton is attached to the ligand A and other to the ligand B. The computer simulated distribution of the complexes in solution has been evaluated.

 

Indian Journal of Chemistry

Vol. 41A, October 2002, pp.2092-2094

 

Synthesis, characterization, thermal decomposition and kinetic parameters of Ni(II) and Cu(II) terephthalate-8Hq complexes

A P Mishra, V K Tiwari & R Singhai*

Ni(II)-8Hq terephthalate and Cu(II)-8Hq terephthalate complexes have been synthesised and characterized by elemental analysis, magnetic measurements, IR spectra and UV- Vis-spectra. The complexes have also been analysed thermogravimetrically for the evaluation of their decomposition kinetic parameters. The thermal decomposition of the compounds occurs mainly in two steps. Kinetic parameters, (E*,Z and D S*) have been determined by using three different methods.

Indian Journal of Chemistry

Vol. 41A, October 2002, pp.2095-2099

 

Photooxidation of substituted purines in presence of peroxydisulphate in aqueous solution

Midudhula Sudha Swaraga  & Mundra Adinarayana*


Photooxidation of purine bases, viz., caffeine, theobromine, theophylline, xanthine, hypoxanthine, adenine and guanine in aqueous solution has been carried out in presence of peroxydisulphate (PDS). Peroxydisulphate is activated to SO4·- at 254 nm. The reactions are followed by measuring the absorbance of purine bases at their respective lmax. The rates of reactions are calculated under different experimental conditions. The light intensity is measured using peroxydisulphate solution as standard chemical actinometer. Using reaction rate and light intensity at 254 nm, the quantum yields are calculated. The rates of photooxidation of purine bases are found to increase with increase in [PDS] and independent of [purine]. The increase of light intensity has been found to increase the rate of oxidation. The quantum yields are found to depend on [purine] but independent of [PDS] and light intensity. On the basis of experimental results a probable mechanism is suggested in which peroxydisulphate on photolysis gives sulphate radical anion which initiates the reaction by capturing an electron from C8 position of purine to form purine radical cation. This radical cation deprotonates and undergoes further oxidation to give C(8) hydroxy purine.