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ACID CATALYSIS AND NITRATE ION EFFECT ON AQUATION OF MALEATO-PENTAAMMINECOBALT(III) AND FUMARATO-PENTAAMMINECOBALT(III) COMPLEXES

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Title ACID CATALYSIS AND NITRATE ION EFFECT ON AQUATION OF MALEATO-PENTAAMMINECOBALT(III) AND FUMARATO-PENTAAMMINECOBALT(III) COMPLEXES
 
Creator CHATTERJEE, C
STEPHEN, M
 
Subject mechanism
kinetics
 
Description The kinetics of dissociation of maleate and fumarate from the maleato- and fumarato-pentaamminecobalt (III) complexes have been investigated in aqueous perchloric acid (0.1 to 0.7 mol dm-3) over a temperature range of 60-80-degrees-C at an ionic strength of 1.0 mol dm-3 adjusted with sodium perchlorate. Variation of observed pseudo first order rate constants on [acid] suggests operation of two concurrent path with k(obs) = k1 + k2[H+], where k1 and k2 are the rate constants for the uncatalysed and acid-catalysed pathways respectively. Under identical conditions, fumaratopentaamminecobalt (III) complex is more reactive than maleatopentaamminecobalt (III) complex. The influence of free carboxylic proton and nitrate ion effect on the rate of substitution reactions have been discussed. Analysis of the rate data corresponding to k2 suggests a dissociative mechanism involving the protonated species (protonation on the adjacent carbonyl oxygen and not on the carboxylate oxygen). The solvent isotope effect, k(D2O)/k(H2O) for the dissociation process is 2.6, consistent with a mechanism involving a rapid pre-equilibrium protonation step followed by a slow rate-determining dissociation. Mechanisms involving concerted attack by H+ and H2O are excluded.
 
Publisher COUNCIL SCIENTIFIC INDUSTRIAL RESEARCH
 
Date 2011-07-20T11:56:03Z
2011-12-26T12:51:28Z
2011-12-27T05:36:42Z
2011-07-20T11:56:03Z
2011-12-26T12:51:28Z
2011-12-27T05:36:42Z
1991
 
Type Article
 
Identifier INDIAN JOURNAL OF CHEMISTRY SECTION A-INORGANIC BIO-INORGANIC PHYSICAL THEORETICAL & ANALYTICAL CHEMISTRY, 30(12), 1005-1009
0376-4710
http://dspace.library.iitb.ac.in/xmlui/handle/10054/5465
http://hdl.handle.net/10054/5465
 
Language en