Kinetics and Mechanism of Ruthenium(III) Catalyzed Oxidation of LProline by Hexacyanoferrate(III) in Aqueous Alkali
TL;DR: In this article, the rate law of ruthenium(III) catalyzed oxidation of L-proline by hexacyanoferrate (III) in alkali was studied spectrophotometrically.
Abstract: Kinetics of ruthenium(III) catalyzed oxidation of L-proline by hexacyanoferrate(III)(HCF) in alkali was studied spectrophotometrically at 30 0 C. A reaction was found to be independent upon (L-proline). The reaction was occurred without intervening free radical. Since unit order each in (Ru(III)) and (HCF), the oxidation follows an outer-sphere mechanism. A suitable mechanism was proposed and rate law was derived as kobs = kK
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Book•
01 Jan 1975
TL;DR: In this paper, the photochemical reactions of coordination compounds are described. But they do not consider the effects of transition metals on coordination compounds, such as diazenes and diazo compounds.
Abstract: Diastereoisomerism and diastereoselectivity in metal complexes.- Mechanistic aspects of the photochemical reactions of coordination compounds.- Complexation and activation of diazenes and diazo compounds by transition metals.
132 citations
TL;DR: In this paper, a 1:1 intermediate complex between l-asparagine and an alkali-permanganate species in a pre-equilibrium step was confirmed by both spectral and kinetic evidence.
Abstract: Kinetic investigations on the oxidation of l-asparagine (Asn) by alkaline permanganate have been carried out spectrophotometrically at a constant ionic strength and temperature. The reaction is first order with respect to [MnO4
−] and less than unit order with respect to both [Asn] and [alkali]. The influence of pH indicated that the oxidation is base catalyzed. The reaction rate was found to increase with increasing ionic strength and temperature. The addition of alkali metal ion catalysts accelerates the oxidation rate. The proposed reaction mechanism involves the formation of a 1:1 intermediate complex between l-asparagine and an alkali-permanganate species in a pre-equilibrium step, which was confirmed by both spectral and kinetic evidence. The complex decomposes slowly in a rate determining step, resulting in the formation of a free radical. The latter reacts again with another alkali-permanganate species in a subsequent fast step to yield the final reaction products which were identified as aldehyde (α-formyl acetamide), ammonia, manganate(VI) and carbon dioxide. The appropriate rate laws are deduced. The reaction constants involved in the mechanism were evaluated. The activation and thermodynamic parameters were determined and discussed.
27 citations
TL;DR: In this paper, the kinetics and mechanism of alginate polysaccharide (Alg) by alkaline hexacyanoferrate (III) in basic solutions at a constant ionic strength of 1.0 Ã 0.0 m −3 have been investigated spectrophotometrically.
Abstract: The kinetics and mechanism of oxidation of alginate polysaccharide (Alg) by alkaline hexacyanoferrate(III) in basic solutions at a constant ionic strength of 1.0 mol dm −3 have been investigated spectrophotometrically. The experimental results showed complex kinetics, where the reaction time curves of the pseudo first-order plots were found to be of sigmoidal S-shape nature. The initial parts of the plots were relatively fast, followed by slow-linear portions after short time periods. The oxidation rates were increased with increasing the alkali concentration indicating that the oxidation is base-catalyzed. A kinetic evidence for formation of 1:1 intermediate complexes was revealed. The activation parameters have been evaluated and a tentative reaction mechanism consistent with the kinetic results is suggested and discussed.
7 citations
TL;DR: The results show that the rate of degradation increases linearly with the increase in concentrations of oxidant and dye at optimum pH 9.0 and constant temperature of 40 ± 0.1°C.
Abstract: In the present work, the degradation of metanil yellow, an azo dye, by hexacyanoferrate(III) ions (oxidant) in the aqueous alkaline medium has been investigated by kinetic-spectrophotometric method at λmax 435 nm of the reaction mixture. The effect of various parameters such as the concentration of dye, oxidant, and solution pH on the reaction rate has been determined. The results show that the rate of degradation increases linearly with the increase in concentrations of oxidant and dye at optimum pH of 9.0 and constant temperature of 40 ± 0.1°C. Thermodynamic parameters such as energy of activation, enthalpy of activation, entropy of activation, and energy of formation have been calculated by studying the reaction rate at four different temperatures, that is, 40-55°C. Based on the experimental results, a plausible reaction mechanism involving complex formation has been proposed and a rate law has been derived. UV-Vis and LC-MS methods of analysis of degradation products show the formation of simpler and less hazardous degradation products. PRACTITIONER POINTS: It is also observed that the time required for azo dye degradation by the present method is about ten times less than the reported methods. Thus degradation of azo linkage and formation of simple and less hazardous products (efficient degradation of dye) makes it a novel method.
5 citations
References
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TL;DR: The finding that the amino acid proline is an effective asymmetric catalyst for the direct aldol reaction between unmodified acetone and a variety of aldehydes is reported.
Abstract: Most enzymatic transformations have a synthetic counterpart. Often though, the mechanisms by which natural and synthetic catalysts operate differ markedly. The catalytic asymmetric aldol reaction as a fundamental C-C bond forming reaction in chemistry and biology is an interesting case in this respect. Chemically, this reaction is dominated by approaches that utilize preformed enolate equivalents in combination with a chiral catalyst.1 Typically, a metal is involved in the reaction mechanism.1d Most enzymes, however, use a fundamentally different strategy and catalyze the direct aldolization of two unmodified carbonyl compounds. Class I aldolases utilize an enamine based mechanism,2 while Class II aldolases mediate this process by using a zinc cofactor.3 The development of aldolase antibodies that use an enamine mechanism and accept hydrophobic organic substrates has demonstrated the potential inherent in amine-catalyzed asymmetric aldol reactions.4 Recently, the first small-molecule asymmetric class II aldolase mimics have been described in the form of zinc, lanthanum, and barium complexes.5,6 However, amine-based asymmetric class I aldolase mimics have not been described in the literature.7 Here we report our finding that the amino acid proline is an effective asymmetric catalyst for the direct aldol reaction between unmodified acetone and a variety of aldehydes. Recently we developed broad scope aldolase antibodies that show very high enantioselectivities, have enzymatic rate accelerations, and use the enamine mechanism of class I aldolases.4 During the course of these studies, we found that one of our aldolase catalytic antibodies (Aldolase Antibody 38C2, Aldrich) is an efficient catalyst for enantiogroup-differentiating aldol cyclodehydrations of 2,6-heptanediones to give cyclohexenones, including the Wieland-Miescher ketone.8,9 These intramolecular reactions are also catalyzed by proline (Hajos-Eder-Sauer-Wiechert reaction)10 and it has been postulated that they proceed via an enamine mechanism.11 However, the proline-catalyzed direct intermolecular asymmetric aldol reaction has not been described. Further, there are no asymmetric small-molecule aldol catalysts that use an enamine mechanism.7 Based on our own results and Shibasaki’s work on lanthanum-based small-molecule aldol catalysts,4,6 we realized the great potential of catalysts for the direct asymmetric aldol reaction. We initially studied the reaction of acetone with 4-nitrobenzaldehyde. Reacting proline (30 mol %) in DMSO/acetone (4:1) with 4-nitrobenzaldehyde at room temperature for 4 h furnished aldol product (R)-1 in 68% yield and 76% ee (eq 1). This result
2,283 citations
Additional excerpts
...Keywords: Ruthenium(III), L-proline, hexacyanoferrate(III), catalysis, ruthenium(III) complexes....
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Book•
01 Dec 1961
TL;DR: In this paper, the authors present a treatment of reaction rates in elementary processes: simple gas-phase reactions, complex reaction in solution, and homogeneous catalysts, and chain reactions.
Abstract: Empirical Treatment of Reaction Rates. Experimental Methods and Treatment of Data. Elementary Processes: Molecular Collisions. Elementary Processes: Potential Energy Surfaces and Transition--State Theory. Simple Gas--Phase Reactions--Interplay of Theory and Experiment. Reactions in Solution. Complex Reactions. Homogeneous Catalysts. Chain Reactions. Photochemistry. Appendix.
2,142 citations
"Kinetics and Mechanism of Ruthenium..." refers background in this paper
...The large positive value of S # , 135 JK -1 mol -1 indicates [28] that activated complex might have gained more degrees of freedom than its reactants, which might be highly disordered....
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Book•
01 Jan 1956
TL;DR: Inorganic spot test analysis has been extensively studied in the literature, see as discussed by the authors for a survey of the current state and prospects of inorganic inorganic spot-test analysis, including preliminary orientational tests for the elements, their ions and compounds.
Abstract: Development, present state and prospects of inorganic spot test analysis. Methodology of spot test analysis (completely revised and enlarged by Dr. G. Skalos). Preliminary orientational tests. Tests for the elements, their ions and compounds. Application of spot reactions in tests of purity, examination of technical materials, studies of minerals. Tabular summary.
1,663 citations
TL;DR: Spot Tests in Organic AnalysisBy Prof. Fritz Feigl.
Abstract: Spot Tests in Organic Analysis By Prof. Fritz Feigl. Sixth, enlarged and revised English edition. Translated by Prof. Ralph E. Oesper. Pp. xx + 675. (Amsterdam: Elsevier Publishing Company; London: D. Van Nostrand Company, Ltd., 1960.) 65s.
493 citations
"Kinetics and Mechanism of Ruthenium..." refers methods in this paper
...Progress of the reaction was followed spectrophotometrically by measuring decrease in the absorbance of HCF at its max 420 nm....
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