Pub Date : 2002-01-01DOI: 10.1080/1028662021000003865
Kabir-ud-din, A. Morshed, Z. Khan
Chromic acid oxidation of d (+)-xylose in water and in presence of surfactants has an induction period followed by autoacceleration. The kinetics and mechanism of the induction period have been studied spectrophotometrically in both media. Due to precipitate formation, the effect of cetyltrimethylammonium bromide (CTAB, cationic) cannot be studied whereas the oxidation rate increased with increase in sodium dodecyl sulphate (SDS, an-ionic) and octylphenoxypolyethoxy ethanol (TX-100, nonionic) concentration. Reaction is routed through the same mechanism as shown by the kinetic study in the absence and presence of surfactants. Micellar catalysis has been traced to partitioning of the chromic acid species and xylose between the aqueous and micellar pseudo-phases. Rate enhancement in SDS micelles is decreased by ammonium, lithium and sodium ions. Micellar binding/association constants and activation parameters were evaluated and discussed. A mechanism consistent with the results is proposed.
{"title":"Micellar Effects on the Chromium(VI) Oxidation of d (+)-Xylose","authors":"Kabir-ud-din, A. Morshed, Z. Khan","doi":"10.1080/1028662021000003865","DOIUrl":"https://doi.org/10.1080/1028662021000003865","url":null,"abstract":"Chromic acid oxidation of d (+)-xylose in water and in presence of surfactants has an induction period followed by autoacceleration. The kinetics and mechanism of the induction period have been studied spectrophotometrically in both media. Due to precipitate formation, the effect of cetyltrimethylammonium bromide (CTAB, cationic) cannot be studied whereas the oxidation rate increased with increase in sodium dodecyl sulphate (SDS, an-ionic) and octylphenoxypolyethoxy ethanol (TX-100, nonionic) concentration. Reaction is routed through the same mechanism as shown by the kinetic study in the absence and presence of surfactants. Micellar catalysis has been traced to partitioning of the chromic acid species and xylose between the aqueous and micellar pseudo-phases. Rate enhancement in SDS micelles is decreased by ammonium, lithium and sodium ions. Micellar binding/association constants and activation parameters were evaluated and discussed. A mechanism consistent with the results is proposed.","PeriodicalId":54977,"journal":{"name":"Inorganic Reaction Mechanisms","volume":"3 1","pages":"255-266"},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59826918","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-01-01DOI: 10.1080/1028662021000020244
D. Bilehal, Raviraj M. Kulkarni, S. Nandibewoor
The kinetics of oxidation of bromate by diperiodatonickelate(IV) (DPN) in alkaline medium at a constant ionic strength has been studied spectrophotometrically. The reaction between DPN and bromate in alkaline medium exhibits 1:1 stoichiometry (DPN:bromate). The reaction shows first order dependence on [DPN] and zero order dependence in [bromate] and less than unit order dependence in alkali concentrations. Periodate has a retarding effect on the rate of reaction. Reaction rate increases with increase in ionic strength and decrease in solvent polarity of the medium. Initial addition of reaction products did not affect the rate significantly. A mechanism involving the monoperiodatonickelate(IV) (MPN) as the reactive species of the oxidant has been proposed. The reaction constants involved in the mechanism are evaluated. The activation parameters were computed with respect to the slow step of the mechanism.
{"title":"Kinetics and Mechanism of Oxidation of Bromate by Diperiodatonickelate(IV) in Aqueous Alkaline Medium--A Simple Method for Formation of Perbromate","authors":"D. Bilehal, Raviraj M. Kulkarni, S. Nandibewoor","doi":"10.1080/1028662021000020244","DOIUrl":"https://doi.org/10.1080/1028662021000020244","url":null,"abstract":"The kinetics of oxidation of bromate by diperiodatonickelate(IV) (DPN) in alkaline medium at a constant ionic strength has been studied spectrophotometrically. The reaction between DPN and bromate in alkaline medium exhibits 1:1 stoichiometry (DPN:bromate). The reaction shows first order dependence on [DPN] and zero order dependence in [bromate] and less than unit order dependence in alkali concentrations. Periodate has a retarding effect on the rate of reaction. Reaction rate increases with increase in ionic strength and decrease in solvent polarity of the medium. Initial addition of reaction products did not affect the rate significantly. A mechanism involving the monoperiodatonickelate(IV) (MPN) as the reactive species of the oxidant has been proposed. The reaction constants involved in the mechanism are evaluated. The activation parameters were computed with respect to the slow step of the mechanism.","PeriodicalId":54977,"journal":{"name":"Inorganic Reaction Mechanisms","volume":"4 1","pages":"103-109"},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/1028662021000020244","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59826926","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-01-01DOI: 10.1080/1028662021000062554
W. Jackson, Leigh J. McJames, P. Newitt, Kerrina Wells
The rates and steric course for the Me 2 SO substitution reactions for cis - and trans -[Co(en) 2 (OSMe 2 )(N 3 )] 2+ in solvent Me 2 SO have been investigated by 1 H NMR and Vis./UV spectroscopy. Isomerisation, racemisation, solvent exchange and NH scrambling experiments for selectively-deuterated complexes are reported which provide a wider picture on the octahedral substitution process and the nature of the intermediates than previously possible. The results show that the traditional accounts appearing in standard texts are in need of revamping.
{"title":"Probing Memory Effects in Octahedral Substitution Reactions: New Handles on Rearrangement Processes","authors":"W. Jackson, Leigh J. McJames, P. Newitt, Kerrina Wells","doi":"10.1080/1028662021000062554","DOIUrl":"https://doi.org/10.1080/1028662021000062554","url":null,"abstract":"The rates and steric course for the Me 2 SO substitution reactions for cis - and trans -[Co(en) 2 (OSMe 2 )(N 3 )] 2+ in solvent Me 2 SO have been investigated by 1 H NMR and Vis./UV spectroscopy. Isomerisation, racemisation, solvent exchange and NH scrambling experiments for selectively-deuterated complexes are reported which provide a wider picture on the octahedral substitution process and the nature of the intermediates than previously possible. The results show that the traditional accounts appearing in standard texts are in need of revamping.","PeriodicalId":54977,"journal":{"name":"Inorganic Reaction Mechanisms","volume":"26 1","pages":"141-157"},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59827368","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
B. Saha, M. Ali, S. Gangopadhyay, Nizamuddin Shaikh, P. Banerjee
The kinetics of the oxidation of complexes, [Fe(H 2 L) 2+ and [Ni(HL')] 2+ (H 2 L u = u 3,14-dimethyl-4,7,10,13-tetraazadeca-3,13-diene-2,5-dione-dioxime, (I)) and HL'=15-amino-3-methyl-4,7,10,13-tetraazapentadec-3-ene-2-one-oxime, (II)) by peroxodisulfate ion was studied spectrophotometrically under pseudo-first-order conditions keeping the complexes as minor components, within the pH range 3.0-7.93 at I =0.20 u mol u dm m 3 (NaClO 4 ) for the former and I =0.25 u mol u dm m 3 for the latter complex at 303 u K. At a particular pH, plots of k obs vs. [S 2 O 8 2 m ] yield ascending curves with decreasing slope values for both the reactions, and the general rate law: d/d t [complex]=2 kQ [S 2 O 8 2 m ]/(1+ Q [S 2 O 8 2 m ]) is followed. A pre-equilibrium ion-pair formation between the reactants prior to electron transfer is proposed. A plot of m [log( k 12 / W 12 ) m 1/2 u log u k 22 ] vs. 1/2 u log( K 12 f 12 ) for such reactions yields a straight line with slope m (0.73 - 0.10) which deviates significantl...
在伪一阶条件下，以小组分的形式研究了配合物[Fe(h2 L) 2+和[Ni(HL')] 2+ (h2 L u = 3,14-二甲基-4,7,10,13-四氮杂碳-3,13-二烯-2,5-二酮-二肟，(I))和HL'=15-氨基-3-甲基-4,7,10,13-四氮杂碳-3-烯-2-一肟，(II))被过氧化物二磺酸离子氧化的动力学。pH值范围内3.0 - -7.93 = 0.20 u摩尔dm我3 (NaClO 4)前我= 0.25 u摩尔dm 3后者复杂303 u k . pH值在一个特定的块奥林匹克广播服务公司与k [S 2 O 8 2 m]收益率上升与下降斜率值的反应曲线,和一般速率定律:d / d t(复杂的)= 2 kQ [S 2 O 8 2 m] / (1 + Q [S 2 O 8 2 m])之后。在电子转移之前，反应物之间形成了一个预平衡离子对。这类反应的m [log(k 12 / W 12) m 1/2 u log u k 22]与1/2 u log(k 12 f 12)的曲线得到斜率为m(0.73 - 0.10)的直线。
{"title":"Electron Transfer Reactions Between Peroxodisulfate-and Iron(II) and Nickel(II)-oxime-imine Complexes--a Kinetic Study","authors":"B. Saha, M. Ali, S. Gangopadhyay, Nizamuddin Shaikh, P. Banerjee","doi":"10.1080/10286620210353","DOIUrl":"https://doi.org/10.1080/10286620210353","url":null,"abstract":"The kinetics of the oxidation of complexes, [Fe(H 2 L) 2+ and [Ni(HL')] 2+ (H 2 L u = u 3,14-dimethyl-4,7,10,13-tetraazadeca-3,13-diene-2,5-dione-dioxime, (I)) and HL'=15-amino-3-methyl-4,7,10,13-tetraazapentadec-3-ene-2-one-oxime, (II)) by peroxodisulfate ion was studied spectrophotometrically under pseudo-first-order conditions keeping the complexes as minor components, within the pH range 3.0-7.93 at I =0.20 u mol u dm m 3 (NaClO 4 ) for the former and I =0.25 u mol u dm m 3 for the latter complex at 303 u K. At a particular pH, plots of k obs vs. [S 2 O 8 2 m ] yield ascending curves with decreasing slope values for both the reactions, and the general rate law: d/d t [complex]=2 kQ [S 2 O 8 2 m ]/(1+ Q [S 2 O 8 2 m ]) is followed. A pre-equilibrium ion-pair formation between the reactants prior to electron transfer is proposed. A plot of m [log( k 12 / W 12 ) m 1/2 u log u k 22 ] vs. 1/2 u log( K 12 f 12 ) for such reactions yields a straight line with slope m (0.73 - 0.10) which deviates significantl...","PeriodicalId":54977,"journal":{"name":"Inorganic Reaction Mechanisms","volume":"3 1","pages":"173-180"},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59827662","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-01-01DOI: 10.1080/10286620290034728
Raviraj M. Kulkarni, D. Bilehal, S. Nandibewoor
The kinetics of the oxidation of sulfamethoxazole (SMZ) by permanganate in aqueous alkaline medium at constant ionic strength of 0.41 mol dm m 3 was studied spectrophotometrically. The reaction is of first order in [permanganate ion] and has apparent less than unit order in both [SMZ] and [alkali]. Addition of products have no significant effect on the reaction rate. However, increasing ionic strength and decreasing dielectric constant of the medium increase the rate. The oxidation in alkaline medium has been shown to proceed via an alkali-permanganate species, which forms a complex with SMZ. The latter decomposes slowly, followed by a fast reaction between a free radical of SMZ and another molecule of permanganate to give the products. The reaction constants involved in the mechanism were evaluated and there is a good agreement between observed rate constants and the calculated rate constants. The activation parameters were computed with respect to the slow step of the proposed mechanism.
{"title":"Kinetic and Mechanistic Study of Oxidation of Sulfamethoxazole by Alkaline Permanganate","authors":"Raviraj M. Kulkarni, D. Bilehal, S. Nandibewoor","doi":"10.1080/10286620290034728","DOIUrl":"https://doi.org/10.1080/10286620290034728","url":null,"abstract":"The kinetics of the oxidation of sulfamethoxazole (SMZ) by permanganate in aqueous alkaline medium at constant ionic strength of 0.41 mol dm m 3 was studied spectrophotometrically. The reaction is of first order in [permanganate ion] and has apparent less than unit order in both [SMZ] and [alkali]. Addition of products have no significant effect on the reaction rate. However, increasing ionic strength and decreasing dielectric constant of the medium increase the rate. The oxidation in alkaline medium has been shown to proceed via an alkali-permanganate species, which forms a complex with SMZ. The latter decomposes slowly, followed by a fast reaction between a free radical of SMZ and another molecule of permanganate to give the products. The reaction constants involved in the mechanism were evaluated and there is a good agreement between observed rate constants and the calculated rate constants. The activation parameters were computed with respect to the slow step of the proposed mechanism.","PeriodicalId":54977,"journal":{"name":"Inorganic Reaction Mechanisms","volume":"3 1","pages":"239-247"},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/10286620290034728","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59827781","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-01-01DOI: 10.1080/1028662021000062572
Kabir-ud-din, M. Akram, Z. Khan
The effect of nonionic Triton X-100 (TX-100) micelles on the pseudo-first order rate constants ( k ) for the oxidation of EDTA by chromic acid has been studied at different perchloric acid concentrations. The micellar-mediated reaction was independent of chromic acid concentration whereas first- and complex-order dependence on [EDTA] and [HClO 4 ], respectively, were observed. Increase in the total concentration of TX-100 from 0.0 to 60.0 2 10 m 3 mol dm m 3 caused the k to increase by nearly 4-fold at constant temperature and [HClO 4 ]. The observed catalytic effect has been explained on the basis of pseudo-phase kinetic and Piszkiewicz models. The higher rate of EDTA oxidation in the micellar pseudo-phase is attributed to association of the reactants with the nonionic micellar head groups through hydrogen bonding. A mechanism is proposed in accordance with the experimental results obtained.
{"title":"Catalytic Effect of Polyoxyethylene t -octylphenol (Triton X-100) Surfactant on the Oxidation of EDTA by Chromic Acid","authors":"Kabir-ud-din, M. Akram, Z. Khan","doi":"10.1080/1028662021000062572","DOIUrl":"https://doi.org/10.1080/1028662021000062572","url":null,"abstract":"The effect of nonionic Triton X-100 (TX-100) micelles on the pseudo-first order rate constants ( k ) for the oxidation of EDTA by chromic acid has been studied at different perchloric acid concentrations. The micellar-mediated reaction was independent of chromic acid concentration whereas first- and complex-order dependence on [EDTA] and [HClO 4 ], respectively, were observed. Increase in the total concentration of TX-100 from 0.0 to 60.0 2 10 m 3 mol dm m 3 caused the k to increase by nearly 4-fold at constant temperature and [HClO 4 ]. The observed catalytic effect has been explained on the basis of pseudo-phase kinetic and Piszkiewicz models. The higher rate of EDTA oxidation in the micellar pseudo-phase is attributed to association of the reactants with the nonionic micellar head groups through hydrogen bonding. A mechanism is proposed in accordance with the experimental results obtained.","PeriodicalId":54977,"journal":{"name":"Inorganic Reaction Mechanisms","volume":"4 1","pages":"187-196"},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59827893","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-01-01DOI: 10.1080/1028662021000062608
Y. Kitamura, Kohji Hyodoh, Yoshihiko Nagawo, Y. Sasaki, N. Azuma
Acid-catalysed hydrolysis kinetics were studied for 14 cobalt(III) carbonato complexes involving the title five at oxonium ion concentration of 0.01-1.0 M, ionic strength of 2.0 (NaClO 4 ) and 15-45°C (M=mol dm m 3 ). Preprotonation constant, about 1 M m 1 , was estimated from a non-linear acidity dependence of an experimental rate constant for the ring-opening of the didentate hydrogencarbonato intermediate. Acidity constant, 0.003-0.7 M, and basicity constant, 0.1-0.9 M m 1 , of the ring-opened aquahydrogencarbonato intermediate were estimated from an acidity dependence of an experimental rate constant for the decarboxylation. Concerning the widely ranging ring-opening rate constants (0.05-126 s m 1 at 25°C), we demonstrate labilizing effects of a reduced charge and of small tetrakis(amine) ligand, correlating with a high activation entropy, as well as of the trans five-membered chelate correlating with a low activation energy. The charge effect may be understood by the solvational change during the dis...
在氧离子浓度为0.01 ~ 1.0 M，离子强度为2.0 (naclo4)，温度为15 ~ 45℃(M=mol dm m3)的条件下，研究了含标题5的14种钴(III)羰基配合物的酸催化水解动力学。预质子化常数约为1 μ M μ 1，由实验速率常数与酸度的非线性关系估计。酸度常数为0.003-0.7 M，碱度常数为0.1-0.9 M / M / 1，通过酸度对实验脱羧速率常数的依赖来估计。关于大范围的开环速率常数(25°C时0.05-126 sm 1)，我们证明了与高活化能相关的还原电荷和小四胺配体以及与低活化能相关的反式五元螯合物的稳定作用。电荷效应可以通过分解过程中的溶剂化变化来理解。
{"title":"Kinetic Study of the Acid-catalysed Hydrolysis of Cobalt(III) Carbonato Complexes with Nonlabile Tetrakis(methylamine), Tetrakis(ethylamine), Fac ( N )-(ethylenediamine)(glycinato), Mer ( N )-(ethylenediamine) (glycinato) or Bis(1,3-propanediamine) Ligands","authors":"Y. Kitamura, Kohji Hyodoh, Yoshihiko Nagawo, Y. Sasaki, N. Azuma","doi":"10.1080/1028662021000062608","DOIUrl":"https://doi.org/10.1080/1028662021000062608","url":null,"abstract":"Acid-catalysed hydrolysis kinetics were studied for 14 cobalt(III) carbonato complexes involving the title five at oxonium ion concentration of 0.01-1.0 M, ionic strength of 2.0 (NaClO 4 ) and 15-45°C (M=mol dm m 3 ). Preprotonation constant, about 1 M m 1 , was estimated from a non-linear acidity dependence of an experimental rate constant for the ring-opening of the didentate hydrogencarbonato intermediate. Acidity constant, 0.003-0.7 M, and basicity constant, 0.1-0.9 M m 1 , of the ring-opened aquahydrogencarbonato intermediate were estimated from an acidity dependence of an experimental rate constant for the decarboxylation. Concerning the widely ranging ring-opening rate constants (0.05-126 s m 1 at 25°C), we demonstrate labilizing effects of a reduced charge and of small tetrakis(amine) ligand, correlating with a high activation entropy, as well as of the trans five-membered chelate correlating with a low activation energy. The charge effect may be understood by the solvational change during the dis...","PeriodicalId":54977,"journal":{"name":"Inorganic Reaction Mechanisms","volume":"4 1","pages":"221-232"},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59827643","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
H. Boukhalfa, F. Thomas, G. Serratrice, C. Béguin
Synopsis : The acid-driven stepwise dissociation kinetics of tris (8-hydroxy-5-sulfonated-quinoline) iron(III) complex and two other 8-hydroxyquinoline derivatives are reported and compared to literature data. The main finding is that, in the rate determining step, the iron-oxygen bond cleavage (oxygen of the hydroxyl group of the ligand) occurs in the transition state with proton transfer to the oxygen of the incipient free ligand oxine in relation with its structure (C-OH). Comparison with literature data shows that for the hydroxamate ligand with its coordinating oxygen involved in C=O, there is no proton transfer during the iron-oxygen bond cleavage in the transition state.The acid hydrolysis reaction rate constants of the mono -oxine iron(III) complexes, with oxine=8-hydroxyquinoline, sulfoxine=8-hydroxy-5-sulfonated-quinoline and fluoro-oxine=5-fluoro-8-hydroxyquinoline, were measured in aqueous solution, 2.0 u M in NaClO 4 at 25°C. Under these conditions, for iron(III)-sulfoxine, the dissociation r...
摘要:报道了三(8-羟基-5-磺化喹啉)铁(III)配合物和另外两种8-羟基喹啉衍生物的酸驱动逐步解离动力学，并与文献数据进行了比较。主要发现是，在速率决定步骤中，铁氧键的裂解(配体羟基的氧)发生在过渡态，质子转移到与其结构(C-OH)有关的初始游离配体氧。与文献数据比较表明，对于配位氧参与C=O的羟酸酯配体，在过渡态的铁氧键劈裂过程中没有质子转移。测定了氧=8-羟基喹啉，亚砜=8-羟基-5-磺化喹啉，氟氧=5-氟-8-羟基喹啉的单氧铁(III)配合物在25℃nacl溶液中2.0 u M的酸水解反应速率常数。在这些条件下，对于铁(III)-亚砜，解离率为…
{"title":"Kinetics of Aqueous Acid Hydrolysis of Iron(III) 5-Substituted-8-Hydroxyquinoline Complexes: Mechanistic Implications","authors":"H. Boukhalfa, F. Thomas, G. Serratrice, C. Béguin","doi":"10.1080/10286620210351","DOIUrl":"https://doi.org/10.1080/10286620210351","url":null,"abstract":"Synopsis : The acid-driven stepwise dissociation kinetics of tris (8-hydroxy-5-sulfonated-quinoline) iron(III) complex and two other 8-hydroxyquinoline derivatives are reported and compared to literature data. The main finding is that, in the rate determining step, the iron-oxygen bond cleavage (oxygen of the hydroxyl group of the ligand) occurs in the transition state with proton transfer to the oxygen of the incipient free ligand oxine in relation with its structure (C-OH). Comparison with literature data shows that for the hydroxamate ligand with its coordinating oxygen involved in C=O, there is no proton transfer during the iron-oxygen bond cleavage in the transition state.The acid hydrolysis reaction rate constants of the mono -oxine iron(III) complexes, with oxine=8-hydroxyquinoline, sulfoxine=8-hydroxy-5-sulfonated-quinoline and fluoro-oxine=5-fluoro-8-hydroxyquinoline, were measured in aqueous solution, 2.0 u M in NaClO 4 at 25°C. Under these conditions, for iron(III)-sulfoxine, the dissociation r...","PeriodicalId":54977,"journal":{"name":"Inorganic Reaction Mechanisms","volume":"3 1","pages":"153-172"},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59828060","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Y. Kitamura, Kohji Hyodoh, Masayuki Hayashi, Yoshihiko Nagawo, Y. Sasaki, A. Shibata
Acid-catalysed hydrolysis kinetics were studied for 10 cobalt(III) complexes bearing a bidentate carbonato ligand at oxonium ion concentration of 0.02-1.0 u M, ionic strength of 2.0 (NaClO 4 ) and 15-45°C (M=mol u dm m 3 ). Preprotonation constant, about 1 u M m 1 , was estimated from a non-linear acidity dependence of the ring-opening velocity of the bidentate hydrogencarbonato intermediate. Acidity constant, 0.005-0.4 u M, and basicity constant, about 0.4 u M m 1 , of the ring-opened aquahydrogencarbonato intermediate were estimated from an acidity dependence of the decarboxylation velocity. Between analogous complexes, ring-opening is faster; activation parameters of ring-opening are lower; and acidity of an aquahydrogencarbonato intermediate is weaker, when the nonlabile quadridentate forms five-membered chelates on the Co(III) center. We believe that a five-membered chelate, especially trans to the hydrogencarbonato, labilizes the hydrogencarbonato chelate by reinforcing the steric strain and that it...
在氧离子浓度为0.02 ~ 1.0 μ M，离子强度为2.0 (naclo4)，温度为15 ~ 45℃(M=mol u dm m3)的条件下，研究了带有双齿碳酸配体的10种钴(III)配合物的酸催化水解动力学。预质子化常数约为1 μ M μ 1，由双齿碳酸盐中间体开环速度的非线性酸度依赖性估计。根据脱羧速度对酸度的依赖性，估计了开环羰基中间体的酸度常数为0.005 ~ 0.4 μ M，碱度常数约为0.4 μ M μ M 1。在类似配合物之间，开环速度更快;开环激活参数较低;当不稳定的四齿化合物在Co(III)中心形成五元螯合物时，碳酸水中间体的酸性较弱。我们认为，五元螯合物，特别是反式到碳氢化合物的螯合物，通过增强位压应变而使碳氢化合物螯合物不稳定。
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Pub Date : 2002-01-01DOI: 10.1080/1028662021000020235
Kabir-ud-din, M. Akram, Z. Khan
Kinetics of the title reaction has been investigated spectrophotometrically in aqueous solution as well as in the presence of cetyltrimethylammonium bromide (CTAB) cationic micelles. The reaction rate is first- and fractional-order with respect to [substrate] and [ninhydrin], respectively, both in the absence and presence of cationic micelles. Whereas SDS addition shows formation of a different product, the reaction of copper(II)-tryptophan complex with ninhydrin is catalyzed by CTAB: the maximum rate enhancement being ca . 5-fold. The data are interpreted in terms of the pseudo-phase model (assuming the association/incorporation of both the reactants at the micellar surface). The binding constants of copper(II)-tryptophan ( K S ) and ninhydrin ( K N ) with CTAB micelles have been calculated. The presence of inorganic salts (NaCl, NaBr, NaNO 3 and Na 2 SO 4 ) leads to a decrease in the rate followed by an increase and it is found that tightly bound/incorporated anions are most effective.
{"title":"Kinetics and Mechanism of the Reaction of Copper(II)-tryptophan Complex with Ninhydrin in Aqueous and Micellar Media","authors":"Kabir-ud-din, M. Akram, Z. Khan","doi":"10.1080/1028662021000020235","DOIUrl":"https://doi.org/10.1080/1028662021000020235","url":null,"abstract":"Kinetics of the title reaction has been investigated spectrophotometrically in aqueous solution as well as in the presence of cetyltrimethylammonium bromide (CTAB) cationic micelles. The reaction rate is first- and fractional-order with respect to [substrate] and [ninhydrin], respectively, both in the absence and presence of cationic micelles. Whereas SDS addition shows formation of a different product, the reaction of copper(II)-tryptophan complex with ninhydrin is catalyzed by CTAB: the maximum rate enhancement being ca . 5-fold. The data are interpreted in terms of the pseudo-phase model (assuming the association/incorporation of both the reactants at the micellar surface). The binding constants of copper(II)-tryptophan ( K S ) and ninhydrin ( K N ) with CTAB micelles have been calculated. The presence of inorganic salts (NaCl, NaBr, NaNO 3 and Na 2 SO 4 ) leads to a decrease in the rate followed by an increase and it is found that tightly bound/incorporated anions are most effective.","PeriodicalId":54977,"journal":{"name":"Inorganic Reaction Mechanisms","volume":"4 1","pages":"77-87"},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59826922","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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