Indian Journal of Chemistry

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

Indian Journal of Chemistry

Vol. 42A, January 2003, pp 7-10

Density functional study of 4-pyrone and 2-pyrone

Piyush K Shukla, Sonia Ralhan & N K Ray*

Density functional (B3LYP) calculations using 6-31G* have been made to estimate the bond lengths and angles for 4-pyrone and 2-pyrone. The predicted bond lengths and angles for 4-pyrone are in excellent agreement with experimental results. However for 2-pyrone, two bond angles are in very poor agreement with the experimental results. Results of MP2 calculations are in good agreement with B3LYP results. Here again the two bond angles for 2-pyrone are very poorly predicted. To confirm this the calculations have been repeated with much larger 6-311+G (d,p) basis set. This again does not change our conclusion. The calculated dipole moments and 13C NMR chemical shifts for 4-pyrone and 2-pyrone are in good agreement with experimental results.

Indian Journal of Chemistry

Vol. 42A, January 2003, pp 11-18

Methyl and vinyl substituted 1H-, 2H-, and 3H-phospholes and their Diels-Alder reactions with ethylene: A semiempirical AM1 study

K Geetha & G Narahari Sastry*

The equilibrium geometries and the relative stabilities of all the possible isomers of phosphole, methylphosphole and vinylphosphole have been estimated using the semiempirical AM1 method. The Diels-Alder transition states and products between each of these isomers, with ethylene as dienophile, have been located. AM1 results show that 2H-phosphole is more stable than 3H-phosphole by 3.6 kcal mol-1 which is in turn more stable than 1H-phosphole by about 6.0 kcal mol-1. The Diels-Alder activation energies of 2H-phospholes are much lower compared to those involving 1H- and 3H-phospholes. Either methyl or vinyl substitution does not alter the broad features in the activation and reaction energies compared to the parent compound.

Indian Journal of Chemistry

Vol. 42A, January 2003, pp 19-29

Extended integral-equation theories for Lennard-Jones fluids

K O Monago* & J P M Trusler

The Percus-Yervick (PY) integral-equation has been extended and used to determine structural and thermodynamic properties of a Lennard-Jones(LJ) fluid. The PY theory has been extended by calculating the coefficients, up to the third-order in density, of the tail function when the latter is expanded as a power series. For a LJ fluid, the resulting integral-equation is exact at the level of the 5th virial coefficient. The properties obtained from the new procedure have been compared with a virial equation of state truncated after the 5th coefficient, computer simulation data and two empirical closures proposed by others. Excellent agreement has been obtained with simulation data for compression factor in the entire gas-phase region, excluding the critical region. The radial distribution function calculated from the method is in very good agreement with simulation data at supercritical temperatures and a density which is greater than the critical value by almost one-third. The tail functions which result from the approximate theories, at super-critical temperatures where data are available for comparison, compare poorly with simulation data at separations within the potential core and at long- range; there is only a fair agreement at intermediate separations at the lowest density examined.

Indian Journal of Chemistry

Vol. 42A, January 2003, pp 30-34

Temporal oscillations and spatial structures in blue bottle experiment

Ishwar Das* & Sujeet Kumar Gupta

Reaction between carbohydrate and methylene blue in an alkaline medium known as blue bottle experiment has been studied in the presence and absence of the polymer polyethylene glycol. We have observed potential changes with time (temporal oscillations). Mosaic structures have been obtained when glucose is taken, may be due to higher percentage of b-anomer. However, no such pattern has been obtained with fructose and cellobiose as these differ from glucose considerably. There is a lower limit of methylene blue (1x10-5M) and a corresponding higher limit of glucose (0.01M) when no such patterns can be obtained. It has been observed that polymer in the medium provides better condition for the simultaneous oxidation reduction process. A simple mechanism has been proposed for the process.

Indian Journal of Chemistry

Vol. 42A, January 2003, pp 35-41

Phase diagram of thermodynamic non-equilibrium state of MgO-B2O3-18%MgCl2-H2O system at 0 ºC

Lixia Zhu, Shiyang Gao* & Shuping Xia

The supersaturated solutions of MgO-B2O3-18%MgCl2-H2O with different mole ratios of MgO:B2O3 have been prepared and kept at 0±0.1ºC. The crystallization paths of boric acid, Mg-borates and Mg-oxychloride from the solutions have been determined by chemical analysis of the solution samples taken at a given time interval during crystallization, and then the liquid-solid phase diagram of thermodynamic non-equilibrium state of MgO-B2O3-18%MgCl2-H2O system at 0 ºC has been constructed. In this phase diagram, five crystallization fields appear, boric acid(H3BO3), mcallisterite (MgO•3B2O3•7.5H2O), hungtsaite (MgO•2B2O3•9H2O), inderite (2MgO•3B2O3•15H2O) and magnesium oxychloride(5Mg(OH)2•MgCl2•8H2O).

Indian Journal of Chemistry

Vol. 42A, January 2003, pp 42-47

Electrochemical oxidation of uracil and 5-halouracils at pyrolytic graphite electrode

Rajendra N Goyal*, Udai P Singh & Adil A Abdullah

Electrochemical oxidation of uracil and 5-halogenated uracils has been investigated in phosphate buffers of pH range 1.2 - 11.0 using linear and cyclic sweep voltammetry, coulometry, controlled potential electrolysis and spectral studies. A single well-defined 6e, 4H+ oxidation peak (Ia) has been observed for uracil whereas halogenated uracils get oxidized in 4e, 3H+ step. The presence of halogen group at 5-position of uracil decreases the electron density at the -bond and the Ep values also shift to less positive potential. The values of the first order rate constant for the disappearance of UV absorbing intermediate have been calculated. The product of electrooxidation has been characterized as alloxan. ECE mechanism has been proposed to account for the formation of alloxan.

Indian Journal of Chemistry

Vol. 42A, January 2003, pp 48-52

One-dimensional infinite chain organotin complexes: Synthesis and structural characterization of triphenyltin(IV) thiophen-2-carboxylate and triphenyltin(IV) 4-pyridinylcarboxylate

Handong Yin*, Chuanhua Wang, Yong Wang & Chunlin Ma

Triphenyltin(IV) thiophen-2-carboxylate (1) and triphenyltin(IV) 4-pyridinylcarboxylate (2) have been synthesized by the reaction of sodium 2-thiophenylcarboxylate and sodium 4-pyridinylcarboxylate with the triphenyltin(IV) chloride and characterized by IR, 1H NMR, MS and single crystal X-ray diffraction. In the crystals of 1, the tin atoms are rendered four-coordinated in a distorted tetrahedral structure. Due to the presence of a close intermolecular Sn…S interaction of 3.339 Å, the structure can be described as a weakly-bridged one-dimensional chain polymer. In the crystals of 2, the tin atom is five-coordinated with bridging pyridine N atom and resulting structure is one-dimensional chain polymer.

Indian Journal of Chemistry

Vol. 42A, January 2003, pp 53-60

Kinetics and mechanism of the reaction of sulphur(IV) with trans-bis-(aqua)(N,N-salicylidiniminato-ortho-phenylenediamine cobaltate(III) : the trans effect of S-bonded sulphite.

Anadi C Dash* & Gouri S Bramha

The reaction of trans-(aqua)(hydroxo)(N,N-salicylidiniminato-ortho-phenylenediamine) cobaltate(III) with SO2 results in the formation of S-bonded monosulphito complex, trans-[Co(salophen) (OH2)(SO3)] as the primary product; the CoIII-S bond formation is concerted with CoIII-O bond breaking. At 25oC, I = 0.5 mol dm3 (NaNO3), the rate and activation parameters for this process are: kSO2 = (4.8 ± 0.4)  108 dm3 mol1 s1, ΔH± = 23.6 ± 3.2 kJ mol1 , ΔS± =  0.14 ± 16.7 J K1 mol1. The aqua-sulphito complex further undergoes substitution of the aqua ligand by imidazole and SO32 ; the formation of the imidazole complex, trans-[Co(salophen)(imH)(SO3)] is , however, reversible. The rate data indicate that the trans- effect of the S-bonded sulphite in trans-[Co(salophen)(OH2)(SO3)] is only marginally stronger for the aqua ligand substitution by imidazole and SO32 than in the case of its salen analogue reported earlier. The kinetic inertness of trans-[Co(salophen)(OH2)(SO3)] towards H+ catalysed aquation in comparison to its salen analogue (kHsalen/kHsalophen = 104 at 25oC) demonstrates the effects of rigidity and extended electron delocalization by the salophen moiety. The rate constants of base hydrolysis of trans-[Co(salophen)(OH)(SO3)]2 at [OH]T= 0.01 – 0.5 , I = 0.5 mol dm3 (25oC) obeys kobs = k0 + kOH [OH] with k0 = (0.89 ± 0.04 )  103 s1 and kOH =( 6.4 ± 0.6 )  103 dm3 mol1 s1. A finite value of k0 indicates that the trans- labilising action of the coordinated OH group is stronger than that of the bound SO32. It is suggested that the second order rate constant kOH, is associated with a mechanism which involves the formation of a reactive C- conjugate base from the aldimine function, H-C=N-R.

Indian Journal of Chemistry

Vol. 42A, January 2003, pp 61-63

Mixed systems showing intermediate nematic phase

Ranjana Vaid, R K Bamezai* & N K Sharma

The intermediate nematic phase has been observed in the mixed systems of liquid crystalline components, which does not show miscibility with the nematic phase of pure component. This phase occurs in a closed region of the temperature-composition field. The components used are various cyano biphenyls and hexyloxy-pentyl phenyl benzoate.

Indian Journal of Chemistry

Vol. 42A, January 2003, pp 64-67

Phase transfer catalysis and kinetics of oxidation of some secondary aromatic alcohols by permanganate in organic media

T D Radhakrishnan Nair* & P Rajendran

Kinetics of oxidation of some 1-aryl ethanols in benzene, toluene, carbon tetrachloride, chloroform, chlorobenzene and dichloromethane have been studied using permanganate ions under phase-transfer catalysis. Tetrabutylammonium bromide (TBAB) and tricaprylmethylammonium chloride (TCMAC) have been used as the phase transfer catalysts (PTC). The corresponding ketones have been formed almost in quantitative yield. The reaction is first order each in oxidant and carbinol concentrations. A unique substituent effect has been observed wherein both the electron-donating and the electron-withdrawing groups enhanced the reaction rate with respect to that of the parent compound. The Hammett substituent constants do not fit into a single linear relation with the rate constants. However, these resolve into two separate linear relations, one for the electron- withdrawing groups and the other for the electron-donating groups.

Indian Journal of Chemistry

Vol. 42A, January 2003, pp 68-71

Synthesis and characterization of functional copolymers of citronellol and methylmethacrylate

A K Srivastava* & Prachi Pandey

The radical copolymerisation of citronellol with methyl methacrylate in xylene at 80 ± 10C for 50 minutes in the presence of azobisisobutyronitrile (AIBN) as well as p-acetylbenzylidene triphenylarsonium ylide (p-ABTAY) follows ideal kinetics and results in the formation of an alternating copolymer in both cases. The overall activation energies with (AIBN) and (p-ABTAY) are 77 kJ/mol and 138 kJ/mol respectively. The copolymer(s) have been characterised by different spectral analyses like IR, NMR, 13C NMR, FTIR, etc. which confirm the existence of alcoholic and ester groups in citronellol and methylmethacrylate respectively. The monomer reactivity ratios, using Kelen-Tüdos method are r1 (MMA) = 0.016 and r2 (citronellol) = 0.0012 using (AIBN) and r1 (MMA) = 0.02 and r2 (citronellol) = 0.001 using (p-ABTAY). The glass transition temperature (Tg) of the copolymer, calculated with the help of differential scanning calorimetry (DSC), is 80oC. The Alfrey- price, Q-e parameters for citronellol has been calculated as 0.1009 and -1.073 for (AIBN) and 0.619 and -2.565 for (p-ABTAY). A possible mechanism of the copolymerisation has been proposed.

Indian Journal of Chemistry

Vol. 42A, January 2003, pp 72-74

Kinetics and mechanism of the oxidative regeneration of carbonyl compounds from oximes by tetramminecopper (II) permanganate

Ashok Kumar, Pallavi Mishra, László Kótai & Kalyan K Banerji*

The oxidative deoximination of several aldo- and keto-oximes by tetraaminecopper (II) permanganate (TACP), in aqueous acetic acid, exhibits a first order dependence each on both the oxime and TACP. Successive scanning of the reaction mixture has shown the presence of an excellent isosbestic point. The oxidation of ketoximes is slower than that of aldoximes. The rates of oxidation of aldoximes correlate well in terms of Pavelich-Taft dual substituent-parameter equation. The low positive value of polar reaction constant indicates a nucleophilic attack by a permanganate-oxygen on the carbon. The reaction is subject to steric hindrance by the alkyl groups. A mechanism involving the formation of a cyclic intermediate, in the rate-determining step, has been proposed.

Indian Journal of Chemistry

Vol. 42A, January 2003, pp 75-78

Solvent-solute interactions in the reaction between p-NO2-benzyl bromide and thiourea -A kinetic study

P Kalyani & P Manikyamba*

The reaction between p-NO2 benzyl bromide and thiourea has been studied in different protic and dipolar aprotic solvents. The reaction is overall second order. Correlation of rate data with different solvent parameters indicates that, the reaction rate is simutaneously influnced by polarity and hydrogen bond donor and aceptor abilities of the solvent. From the linears multiple regression analysis information regarding the relative solvation of the reactants and the transition state is obtained and the solvation model is proposed.

Indian Journal of Chemistry Vol. 42A,

January 2003, pp 79-83

Thermodynamic parameters and stability constants of lanthanide(III) complexes of biologically active glutathione (GSH)

and their chemical speciation

B S Garg, B K Singh, Deo Nandan Kumar & P K Singh*

The stability constants of lanthanide(III) complexes of reduced glutathione (GSH) have been determined by potentiometric estimation of [H+], in aqueous medium at different ionic strengths and at various temperatures. The effect of dielectric constant on stability has been studied at different percentage of solvent variations and at different solvent systems. The and pL values have been calculated by the method of Irving and Rossotti. Computation of stability constants are carried out on an IBM compatible PC computer using the weighted least squares method. The values of Smin are also evaluated. To visualise the nature of the equilibria involving lanthanide(III) with glutathione, species distribution curves of complexes have been plotted as a function of pH using the program SPE. The order of stability constants is found to be La(III) < Pr(III) < Nd(III) < Gd(III) < Ce(III) < Sm(III) < Tb(III) < Dy(III < Ho(III) < Yb(III).

Indian Journal of Chemistry

Vol. 42A, January 2003, pp 84-88

Charge transfer complexes of 5-aminoindole schiff bases with nitro-aromatic acceptors

R M Issa, M M Ayad*, G B El-Hefnawey & H F Rizk

The solid charge transfer complexes of some schiff bases derived from 5-aminoindole with some dinitro- and trinitrobenzene derivatives as acceptors are prepared. The IR, electronic absorption and 1H NMR spectroscopy are used to characterize these complexes. The spectral changes reveal that the CT interaction depends on the type of both the donor and acceptor. The complexes formed involve π-π*and n-π* electron transfer as well as proton transfer.

Indian Journal of Chemistry

Vol. 42A, January 2003, pp 89-93

Synthesis, characterization and applications of a new phase of crystalline and mercury selective acrylamide cerium(IV) phosphate : A novel fibrous ion exchanger

K G Varshney*, Puja Gupta & Namrta Tayal

A new phase of hybrid material acrylamide cerium(IV) phosphate, prepared in the fibrous form suitable for column preparation has been characterized by TGA, IR, SEM and XRD studies. Its ion exchange behaviour, pH titrations and distribution behaviour have been studied. Distribution studies reveal the exchanger to be highly selective for Hg2+ ion. As a consequence, some binary separations of metal ions have been achieved on a column of this material, demonstrating its analytical potential.

Indian Journal of Chemistry

Vol. 42A, January 2003, pp 94-96

Trace determination of Ni(II) and Co(II) by adsorptive stripping voltammetry using 1-nitroso-2-naphthol

Ravin Jugade & A P Joshi*

A rapid differential pulse adsorptive stripping voltammetric method has been developed for the trace determination of nickel and cobalt. The studies have been carried out in 0.01 M NH4Cl solution at pH 9.5 in a solution containing 1M 1-nitroso-2-naphthol. Two distinct peaks are obtained for nickel and cobalt at -0.39 V and -0.51 V respectively. Under the optimum conditions of accumulation potential, accumulation time, rest period, concentration of ligand, drop size, scan rate, pulse amplitude, the 3 detection limit is found to be 0.2 ppb. The method has been applied to the determination of Ni(II) and Co(II) in spiked water samples, standard alloy samples and various food samples.

Indian Journal of Chemistry

Vol. 42A, January 2003, pp 97-99

Kinetic—spectrophotometric determination of trace amounts of manganese(II) by it’s catalytic effect on the oxidation of methyl orange with periodate

Farzaneh Shemirani* , Fatemeh Razzaz Rahmati & Mohammad Ali Hajimoosa

A kinetic-spectrophotometric method for the determination of trace amounts of Mn(II) has been described based on its catalytic action on the oxidation of methyl orange by periodate. The reaction has been monitored spectrophotometrically by measuring the decrease in absorbance at 474 nm , by the fixed-time method of 5 min from initiation of the reaction . The decrease in absorbance at 474 nm is found to be proportional to the Mn(II) concentration in the range of 4-52 ng ml1, with limit of detection as 0.5 ng ml1, and relative standard deviation for ten replicate analyses of 20 ng ml1 as 3.8%. The method has been used for the determination of Mn(II) in standard soil sample with good accuracy. The effect of interfering cations and anions has also been studied.

Indian Journal of Chemistry

Vol. 42A, January 2003, pp 100-105

Sol-gel synthesis, X-ray, infrared spectra and electrical conductivity of lanthanum/barium-cobaltite systems

M Sh Khalil

Cubic perovskite-type pure lanthanum cobaltite, LaCoO3, LC, and barium-substituted lanthanum of the chemical formula La1-xBaxCoO3, LBC, x = 0.0 (LC), 0.1, 0.3, 0.5, 0.8, 1.0, powders are prepared using the polymerized complex technique at relatively low temperature. The complex solution, with molar ratios La (Ba) / Co/ CA (citric acid) / EG (ethylene glycol) = 1: 1: 10: 40, is heated at 130°C to produce a dark Prussian transparent polymeric gel without any precipitation. Pyrolysis of the gel at 350°C gave a powder precursor of LC or LBC. Thermal analyses, X-ray diffraction and IR- spectroscopy indicate the formation of single phase cubic LC or LBC when their precursors are heat-treated in air at temperatures > 500° / 2h. For comparison, a solid-state reaction sample, LC, has been prepared, where traces of the parent oxides appear even at higher sintering temperature (900°C). The lattice vibrations in LC precursor are heat-treated at different temperatures and LBC as a function of Ba-additions indicate the structural changes with temperature or barium effect respectively. The amounts of metals determined by AAS, in the samples after annealing confirm the composition to be LaCoO3 at 900°C. The electrical conductivity σ, of the ceramic LBC formed at 900°C/2h, as a function of Ba-content (x), has been measured at temperatures, 20 (room temp.), 100, 200 and 300°C.

From the results, it is found that σ increases with the measuring temperature while substitution of La- for Ba- is effective for enhancing the oxide ion conductivity in the range 0 < x < 0.5 where it decreases with further increase of x.

Indian Journal of Chemistry

Vol. 42A, January 2003, pp 106-108

Corrosion behavior of carbon steel in DTPMP inhibited neutral Medium

Vandana Rai & Krishna S Pitre*

Corrosion rate for mild steel in neutral medium (model water) has been studied using a new voltammetric procedure. The synergistic effect of Zn++ ion with DTPMP inhibitor has revealed favourable results. Corrosion rate has been determined as a function of time, using gravimetric and electrochemical methods. The corrosion inhibition efficiency of DTPMP+Zn is found to be 80% after 24h.

Indian Journal of Chemistry

Vol. 42A, January 2003, pp 109-111

Direct and derivative spectrophotometric determination of zirconium(IV) with 2,4-dihydroxy benzaldehyde isonicotinoyl hydrazone

S Sivaramaiah, P Raveendra Reddy*, V Krishna Reddy & T Sreenivasulu Reddy

A simple and sensitive spectrophotometric method has been developed for the determination of zirconium(IV) in aqueous medium. The metal ion forms golden yellow coloured, soluble complex with 2,4-dihydroxy benzaldehyde isonicotinoyl hydrazone (2,4-DHBINH) at pH 1.5 with max at 410 nm. Beer’s law is obeyed in the range 0.40 - 4.00 µg ml-1 of Zr(IV). The molar absorptivity and the Sandell’s sensitivity of the method are 1.82 x 104 lit mol-1 cm-1 and 0.005 µg cm-2, respectively. The interference of various ions has been studied. The complex has a 1:2

[Zr(IV) : 2,4-DHBINH] stoichiometry. A method for the determination of zirconium(IV) by first order derivative spectrophotometry has also been proposed.

Indian Journal of Chemistry

Vol. 42A, January 2003, pp 112-115

Analytical properties of 2-acetylthiophene-4-phenyl-3-thiosemicarbazone: Spectrophotometric determination of copper(II) in edible oils and seeds

N B L Prasad, K Hussain Reddy * & T Sreenivasulu Reddy

The analytical properties of 2-acetylthiophene-4-phenyl-3-thiosemi-carbazone (ATPT) are described for the first time. The reagent gives yellowish green coloured complex with copper(II) in sodium acetate - acetic acid buffer (pH 3.0 - 6.0) medium. This colour reaction (molar absorptivity, 2.92 x 104 L mol-1 cm-1 at 385 nm) has been investigated for the spectrophotometric determination of copper in edible oils and seeds.

Indian Journal of Chemistry

Vol. 42A, January 2003, pp 116-120

Improved selectivity to orthophosphate, pyrophosphate and triphosphate by adding metal ions to a tripodal ligand

Yan-He Guo, Qing-Chun Ge, Hai Lin, Hua-Kuan Lin*, Shou-Rong Zhu, & Chang-Yue Zhou

The strongly and selectively binding of phosphate (PO), pyrophosphate (PP) and triphosphate (tP) by tripodal ligand N, N, N-tri((2-aminoethyl)thioethyl)amine (L) has been studied in aqueous solution at I = 0.1mol dm-3 KNO3 and 25 oC. The interactions between L and the inorganic substrates are described in detail, with equilibrium constants given for each species formed. The stability constants of 1:1:1 M (M = Cu2+ or Zn2+):L:S (S = PO, PP, tP) are determined by potentiometric pH titrations. In addition, the interactions of Zn(II)/L/phosphate systems are investigated by 31P NMR spectra and Cu(II)/tP/phosphate systems were studied by EPR spectra. The results show that metal ion can act as “messenger” or bridge between the receptor and the substrate, and the existence of metal ion in the ternary systems leads to the competition between the mixed ligands. The metal ion improves the selectivity and recognition of the substrates by protonated tripodal ligand.