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Author

C. Kalidas

Bio: C. Kalidas is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topic(s): Solvation & Solubility. The author has an hindex of 4, co-authored 16 publication(s) receiving 52 citation(s).
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Journal ArticleDOI
S. Subramanian1, C. Kalidas1Institutions (1)
Abstract: The selective solvation of silver(I) bromate in the binary solvent mixtures of methanol + acetonitrile and ethanol + acetonitrile has been studied at 30°C by solubility and emf measurements. The solubility of the salt increases with the addition of acetonitrile up to a mole fraction ( X AN ) of 0.6 and 0.7 in the case of methanol + acetonitrile and ethanol + acetonitrile respectively and then decreases with further addition of the same. The transfer free energy of the silver ion (molal scale) decreases continuously with the addition of acetonitrile in both the mixtures. The transfer free energies of bromate ion (molal scale) are found to be quite small up to X AN ≈ 0.7 in both methanol + acetonitrile and ethanol + acetonitrile mixtures and then increase. The solvent transport number Δ, of acetonitrile is positive with a maximum at X AN = 0.55 (Δ = 2.7) and at X AN = 0.45 (Δ = 2.2) for methanol + acetonitrile and ethanol + acetonitrile systems respectively. These results have been interpreted as arising due to a heteroselective solvation of the salt with the silver ion being preferentially solvated by acetonitrile and the bromate ion by the amphiprotic component which is marked especially at higher compositions.

14 citations


Journal ArticleDOI
Abstract: The electrochemical reduction of 2-nitrobenzidine (I) has been investigated in N,N-dimethylformamide solutions. Two well-defined polarographic waves in the ratio 1:3 were obtained. The first wave was found to be a reversible, diffusion-controlled, single electron wave while the second was the result of a diffusion-controlled, irreversible, three-electron process with chemical complications. The nitro and nitroso anion radical intermediates of I formed during the CPE experiments were detected by an ESR technique and confirmed later by cyclic voltammetry. The “current oscillations” observed in the cyclic voltammograms of I are discussed. An eece-type of sequence is suggested for I reduction leading to the formation of 2-hydroxylaminobenzidine.

12 citations


Journal ArticleDOI
Abstract: The selective solvation of Ag(I) bromate and iodate was studied in dimethyl sulfoxide–water mixtures at 30 °C by solubility and EMF measurements. The solubility of silver bromate decreases down to XDMSO=0.2 and thereafter increases with addition of dimethyl sulfoxide, the solubility of silver iodate continuously decreasing under the same conditions. The transfer free energy of silver cation decreases while that of halate ions increases with the addition of dimethyl sulfoxide. The solvent transport number, Δ, passes through a maximum around XDMSO=0.5 in both cases. These results were interpreted in terms of a heteroselective solvation of both the salts, the silver ion being preferentially solvated by dimethyl sulfoxide and the halate ions selectively hydrated by water in the mixtures.

12 citations


Journal ArticleDOI
C. Kalidas1, R. Raghunath1Institutions (1)
Abstract: The preferential solvation of silver(I)-cryptand-2,2,2 perchlorate complex in methanol (MeOH) + acetonitrile (AN) and water + AN mixtures (25°C) was studied by determination of Gibbs transfer energies and solvent transport numbers over the complete range of solvent compositions. The Gibbs transfer energies of the complex salt were split into ionic components by applying the negligible liquid junction potential (nLJP) assumption and reference electrolyte methods using tetraphenylarsonium tetraphenylborate (TATB) in MeOH + AN and water + AN mixtures respectively. The transfer energy of the complexed cation is negative and decreases continuously with the addition of AN (up to X AN = 0.9 in MeOH + AN mixtures and up to X AN = 0.5 in water + AN mixtures), while that of perchlorate ion increases under the same conditions in both mixed solvents. The solvent transport number Δ AN of AN is positive and passes through a maximum of 5.0 at X AN = 0.55 in MeOH + AN mixtures and 8.7 at X AN = 0.45 in water + AN mixtures. The results suggest a heteroselective solvation of the salt, with the complex cation being selectively solvated by AN and the perchlorate ion by MeOH or water in the two mixed solvents.

4 citations


Journal ArticleDOI
Abstract: The electroreduction of 4-(2-thienyl)quinazoline (4-TQ) in acetonitrile solutions gave a single two-electron well-defined polarographic wave. The well-defined wave was found to be diffusion-controlled and irreversible on the basis of the usual criteria. Based on the controlled-potential electrolysis and cyclic voltammetric experiments, a disproportionation reaction mechanism is suggested for 4-TQ reduction in acetonitrile.

2 citations


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Journal ArticleDOI
John L. Hudson1, Theodore T. Tsotsis2Institutions (2)
Abstract: We review here the status of research on the dynamics of electrochemical reactions. The electrodissolution of metals, cathodic deposition, and electrocatalytic reactions are discussed. We treat dynamic behavior such as periodic oscillations, bifurcations, chaos, and spatial patterns and also the status of mechanisms and mathematical models, which explain the dynamics.

316 citations


Journal ArticleDOI
Yizhak Marcus1Institutions (1)
23 Feb 2000-Chemical Reviews
TL;DR: A critical review of this information and its presentation in a manner that permits comparison of different cations in a given solvent mixture and of a given cation transferring into different mixtures is of value.
Abstract: A large number of quantitative studies have been made of the Gibbs energy of transfer (the solvent medium effect) for cations transferring from water into mixed aqueous−organic solvent systems, mainly at 25 °C. Nevertheless, no systematic effort appears to have been made to compile and analyze these data, particularly for multivalent cations. A critical review of this information and its presentation in a manner that permits comparison of different cations in a given solvent mixture and of a given cation transferring into different mixtures is therefore of value.

164 citations


Journal ArticleDOI
Abstract: The quantification of metal-chelating activity of caffeic and ferulic acids( 1 and 2, resp.) was successfully performed by using a potentiometric system with data-analysis computer programs. The method was applied to two phenolic models, which have been systematically reported as antioxidants. Although a chain-breaking mechanism was proposed, several studies pointed out the possibility of complexation of transition metals that can participate in single-electron reactions and mediate the formation of oxygen-derived free radicals. In this work, the complexation propertiestowardsCu II were investigated by potentiometry with a glass electrode. Acidity constants of the ligands (phenolic acids) and the formation constants of the ligandmetal complexes were evaluated by potentiometry. The modeling of the titration curvesand the data treatment were performed with the computer programsSuperquad and Bes t. A detailed quantitative examination of the complexation species formed in the Cu II /caffeic acid (1) and Cu II /ferulic acid (2) systems is presented together with the formation constants (log ). Results have shown that the complexation properties of the two phenolic acids towardsthe trans ition metal are quite different: the activity of caffeic acid ( 1) wasfound higher than that of ferulic acid (2). The data are important to get insight into the mechanism of action of antioxidants, and, in this case, could partially explain the efficacy of caffeic acid in the protection of LDL oxidative damage. In addition, the analytical method developed could be applied to quantify the chelating activity of important biological compounds, such as allopurinol, uric acid, cinnamic acids, flavonoids, and anthocianins, and, in that way, could be a valuable tool to understand the mechanisms underlying their protective effects.

32 citations


Journal ArticleDOI
Abstract: A systematic and comprehensive study on cyclic voltammetric anodic current oscillation (CVACO) at a hanging mercury drop electrode (HMDE) was carried out for the redox reactions of molecular oxygen (O2), nitrobenzene (NB), 1,4-dinitrobenzene (DNB), benzoquinone (BQ), 2,3,5,6-tetramethylbenzoquinone (TMBQ), benzophenone (BP), azobenzene (AB), 2,1,3-benzothiadiazole (BTD), 7,7,8,8-tetracyanoquinodimethane (TCNQ), methyl viologen dichloride (MV2+), and tris(2,2‘-bipyridine)ruthenium(II) dichloride [Ru(bpy)32+] in dimethyl sulfoxide (DMSO) solutions containing 0.1 M tetraethylammonium perchlorate (TEAP). From the electrocapillary curve (ECC) obtained using a dropping mercury electrode as well as the capacitance versus potential curves measured using electrochemical impedance technique, the value of the potential of zero charge (PZC) was estimated to be −0.27 V versus Ag|AgCl|NaCl (sat.) in a DMSO solution containing 0.1 M TEAP. CVACO was found to occur only for the redox couples (i.e., BP0/BP•-, O20/O2•-, AB0...

26 citations


Journal ArticleDOI
Madhu Sudan Saha1, Yong Che1, Takeyoshi Okajima1, Takanori Kiguchi1  +3 moreInstitutions (1)
Abstract: Electrochemical oscillatory phenomena have been observed in the redox reaction of the O 2 /O 2 − (superoxide ion) couple on a hanging mercury drop electrode (HMDE) in a limited aprotic medium. The current oscillation occurs during the reoxidation process of the electrogenerated O 2 − . It has been found that the observed oscillation is really irregular, complicated and affected by the addition of poly(vinyl chloride) as a maximum suppressor as well as many other experimental factors such as solvent, electrode substrate, concentration of O 2 − in the electrode vicinity and potential scan rate in cyclic voltammetry. The oscillation phenomena have been explained similarly to the maxima in classical polarography (i.e. by streaming phenomena) and in addition, based on the formation–destruction of a passive film on the electrode surface which results in the dissolution of the mercury electrode. The results obtained demonstrate that the electrogeneration and adsorption of O 2 − on HMDE are indispensable for the present oscillation.

18 citations


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Author's H-index: 4

No. of papers from the Author in previous years
YearPapers
19951
19922
19911
19891
19881
19861