G. Bhattacharjee

Determination of cobalt ions at nano-level based on newly synthesized pendant armed macrocycle by polymeric membrane and coated graphite electrode

Poly(vinylchloride) (PVC) based membranes of macrocycles 2,3,4:9,10,11-dipyridine-1,3,5,8,10,12-hexaazacyclotetradeca-2,9-diene (L(1)) and 2,3,4:9,10,11-dipyridine-1,5,8,12-tetramethylacrylate-1,3,5,8,10,12-hexaazacyclotetradeca-2,9-diene (L(2)) with NaTPB and KTpClPB as anion excluders and dibutylphthalate (DBP), benzyl acetate (BA), dioctylphthalate (DOP), o-nitrophenyloctyl ether (o-NPOE) and tri-n-butylphosphate (TBP) as plasticizing solvent mediators were prepared and investigated as Co(2+) selective electrodes. The best performance was observed with the membranes having the composition L(2):PVC:TBP:NaTPB in the ratio of 6:39:53:2 (w/w; mg). The performance of the membrane based on L(2) was compared with polymeric membrane electrode (PME) and coated graphite electrode (CGE). The PME exhibits detection limit of 4.7x10(-8)M with a Nernstian slope of 29.7 mV decade(-1) of activity between pH 2.5 and 8.5 whereas CGE exhibits the detection limit of 6.8x10(-9)M with a Nernstian slope of 29.5 mV decade(-1) of activity between pH 2.0 and 9.0. The response time for PME and CGE was found to be 11 and 8s, respectively. The CGE has been found to work satisfactorily in partially non-aqueous media up to 35% (v/v) content of methanol, ethanol and 25% (v/v) content of acetonitrile and could be used for a period of 4 months. The CGE was successfully applied for the determination of Co(2+) in real and pharmaceutical samples and as an indicator electrode in potentiometric titration of cobalt ion.

A New PVC-Membrane Electrode Based on a Diazatetrathia (N2S4) Macrocyclic Ligand for Selective Determination of Silver Ion

Abstract A poly(vinyl chloride) based membrane based on neutral macrocyclic ionophore: 2,3,4:10,11,12-dipyridine-3,11-diaza-1,5,9,13-tetrathiacyclohexadeca-2,10-diene with sodium tetraphenyl borate (STB) as an anion excluder and dibutylphthalate (DBP) and dioctylphthalate (DOP) as plasticizing solvent mediator was prepared and investigated as a Ag(I)-selective electrode. The best performance was observed with the membrane having the ligand-PVC-DBP-STB composition 1:6:1:2, which worked well over a wide concentration range (3.98 × 10−6 mol L−1−1.00 × 10−1 mol L−1) with a Nernstian slope of 55.3 mV per decade of activity between pH 3.0–7.0. This electrode showed a fast response time of 15 s and was used over a period of three months with good reproducibility (S = 0.3 mV). The selectivity coefficient for mono-, di-, and trivalent cations indicate excellent selectivity for Ag(I) ions over a large number of cations. Anions such as and do not interfere and the electrode also works satisfactorily in a partially nonaqueous medium. The sensor has been used as an indicator electrode in the potentiometric titration of Ag(I) with Nal solution. It has also been used successfully for determination of Ag(I) in real samples.

Effect of surfactants on the cleavage of the N−O bond in O-(2,4-dinitrophenyl) cyclohexanone oxime

Kinetics of cleavage of N−O bond in O-(2,4-dinitrophenyl)-cyclohexanone oxime with hydroxide ions both in the presence and absence of surfactants has been studied. The reaction is accelerated by cationic micelles, slightly by non-ionic micelles and there is no effect of anionic micelles. A plot of the rate constant vs. [surfactant] shows a maximum corresponding to the CMC of surfactant.AbstractБыла исследована кинетика расщепления связи NO в O-(2,4-динитрофенил) циклогексанон-оксиме с помощью гидроксильных ионов как в присутствии, так и в оксутствии поверхностно-активных веществ (ПАВ). Реакция может быть ускорена с помощью катионных мицелл, слегка ускорена с помощью неионных мицелл, а анионные мицеллы не оказывают какого-либо эффекта. На графике зависимости константы скорости от концентрации ПАВ наблюдается максимум, соответствующий ККМ ПАВ.

Nucleophilic cleavage of N-O bond in O-(2, 4-dinitrophenyl)cyclohexanone oxime in aqueous-methanol

Abstract The order of nucleophilic reactivity towards nitrogen in o -(2, 4 - dinitrophenyl) cyclohexanone oxime with various nucleophiles in aqueous-methanol has been found to be: N 2 H 4 >OH - >PhO - >urea>thiourea> SO 3 - >CH 3 COO - >NO 2 - >S 2 O 3 2- >SCN - >Cl - >Br - . A SN 2 type of reaction involving a polar transition state on the oxime N is indicated. Bronsted relationship is applicable (β = 0.09). The substrate is reducible at the dropping mercury electrode. Kinetics of the reaction has been followed both spectrophotometrically and polarographically with excellent conformity.

Synthesis, Characterisation and Kinetic Studies ofAcid-promoted Dissociation Reactions of the Nickel(II)Complex of a [Me4(14)-tetraene-N4]Macrocyclic Ligand

The kinetics of acid-promoted dissociation reactions of Ni II complex cations of an Me 4 -tetraene macrocyclic ligand follow good first-order reactions with acids in various solvents with the rate of reaction proceeding faster in media of higher dielectric constant.

Solvent effect on the kinetics of the reaction of 2,3-[9,10-dihydroanthracene-endo-9,10-diyl]-N-(2,4-dinitrophenoxy)succinimide with piperidine

The kinetics of the reaction between 2,3-(9,10-dihydroanthracene-endo-9,10-diyl)-N-(2,4-dinitrophenoxy)succinimide and piperidine have been studied in acetonitrile, ethyl acetate, benzene, dioxane, and methanol at 35 ± 0.1 °C. The second-order rate coefficient increases with increased piperidine concentration in all cases except for methanol. The observed base catalysis in acetonitrile, ethyl acetate, benzene and dioxane is explained in terms of the rate-limiting nucleofuge detachment. For the case of methanol, due to its high hydrogen-bond donating property, the formation of the intermediate is rate determining.

Kinetics of reactions of o-(2,4-dinitrophenyl) benzaldoximes with methylamine, cyclohexylamine and piperdine. Reactivity at different electrophilic sit

Abstract Kinetics of reaction of E-O-(2,4-dinitrophenyl) benzaldoximes [X-C6H4-CH = N-O-C6H3(NO2)2 (2:4) ; where X = H, p-Me, p-Cl, p-NO2] have been studied with MeNH2,cyclohexylamine (CHA) and piperdine (PiP) in 1:1 ( v v ) ethanol-water at 35±0.1°C under pseudo first order conditions. The reactions are overall second order, first order with respect to each reactant. Hammett plots are linear with a ϱ value of +0.75 for MeNH2, +0.61 for CHA and +1.25 for PiP. MeNH2 and CHA predominantly give the corresponding N-(2,4-dinitro-phenyl)amine with attack at the aromatic carbon in sharp contrast to earlier observation with OH-. With piperdine both elimination and substitution products are obtained, the former product predominanting when strong electron-withdrawing substituents are present in the phenyl ring of the oxime.