Dissociation kinetics of metal complexes in acid. Copper complexes of triazamacrocycles

1981 ◽  
Vol 34 (2) ◽  
pp. 291 ◽  
Author(s):  
PG Graham ◽  
DC Weatherburn
Keyword(s):  
Aqueous Solution ◽  
Copper Complexes ◽  
Activation Parameters ◽  
Macrocyclic Complex ◽  
Acid Dissociation ◽  
General Mechanism ◽  
Dissociation Kinetics ◽  
First Order ◽  
High Concentrations ◽  
Kinetics Of

The acid dissociation kinetics of the mono-copper complexes of 1,4,7-triazacyclononane, znn; 1,4,7-triazacyclodecane, zdn; 1,4,8-triazacycloundecane, zud; 1,5,9-triazacyclododecane, zdd; 2,2,4-trimethyl-1,5,9-triazacyclododecane, tmzdd; 1,5,9-triazacyclotridecane, ztd; and cyclohexane- r-1,c-3,c-5 triamine, ccha, were studied in aqueous solution over a range of acid concentrations (0.025-0.5 mol dm-3), I 1.0 (NaN03). A variety of kinetic behaviour is observed. Cu(znn)2+, Cu(zdn)2+ and Cu(zud)2+ display a first-order dependence upon [H+] with kH (298 K) 51 dm3 mol-1 s-1 (znn), 17 dm3 mol-1 s-1 (zdn), and 5.6 dm3 mol-1 s-1 (zud). Cu(zdd)2+, Cu(ztd)2+ and Cu(ccha)2+ show a dependence on [H+] at low acid concentrations but become acid-independent at high concentrations. The acid-independent rate constants are k1 (298 K) 2.2 s-1 (zdd), 15.4 s-1 (ztd) and k1 (283 K) 75 s-1 (ccha). Cu(tmzdd)2+ shows a rate law of the form rate = k+kH[H+] with k (298 K) 1.8×10 s-1 and kH (298 K) 2.0×10-3 dm3 mol-1 s-1. Activation parameters have been determined in all cases except Cu(ccha)2+ which was studied at 10�C. The results are compared with other macrocyclic complex systems, and a general mechanism for these reactions is discussed.

Dissociation kinetics of metal complexes in aqueous acid. III. The effects of methyl substitution and chelate ring size on the rates of dissociation of copper(II) triazamacrocyclic complexes

1984 ◽  
Vol 37 (11) ◽  
pp. 2243 ◽  
Author(s):  
PG Graham ◽  
DC Weatherburn
Keyword(s):  
Chelate Ring ◽  
Acid Dissociation ◽  
Ring Size ◽  
Dissociation Kinetics ◽  
Methyl Substitution ◽  
First Order ◽  
Aqueous Acid ◽  
Kinetics Of ◽  
Chelate Ring Size ◽  
Acid Dependence

The acid dissociation kinetics of mono copper(II) complexes of the ligands 2-methyl-1,4,7-triazacyclononane, mznn ; 1,4,7-triazacycloundecane, zaud ; 1,4,7-triazacyclododecane, zadd ; and 1,5,9-triazacyclotetradecane, zted were studied in aqueous solution over a range of acid concentra- tions (0.025-0.5 mol 1-1), I1.0 (NaN03). Cu(mznn)2+ displays a first-order dependence on [H+] with kH (298 K) 26 1. mol-1 s-1. The other complexes show an acid dependence at low [H+] but become independent of acid at higher concentrations. The acid-independent rate constants k1 were determined to be Cu(zaud)2+, 67 s-1 (280 K); Cu(zadd)2+, 45 s-1 (298 K); Cu(zted)2+ 50 s-1 (298 K). The results are compared with those obtained with other copper(II) triazamacro- cyclic complexes.

Dissociation kinetics of metal complexes in acid. II. Copper complexes of linear polyamines

1983 ◽  
Vol 36 (3) ◽  
pp. 433 ◽  
Author(s):  
DC Weatherburn
Keyword(s):  
Nitrogen Atom ◽  
Copper Complexes ◽  
Activation Parameters ◽  
Decomposition Kinetics ◽  
Acid Decomposition ◽  
Dissociation Kinetics ◽  
Rate Determining Step ◽  
Kinetics Of ◽  
Nitrogen Bond ◽  
Chelate Rings

The acid decomposition kinetics of the monocopper complexes of 20 different linear polyamines have been studied over a range of acid concentrations (0.025 to 0.5 mol dm-3), I 1.0 (NaNO3). Complexes which contain only six-membered chelate rings reacted at a rate which is independent of acid concentration. Complexes with five-membered chelate rings have rate constants which show a non-linear dependence on H+ concentration. Activation parameters have been determined for some complexes. A mechanism, in which the breaking of the first copper-nitrogen bond or the subsequent protonation of the nitrogen atom is the rate-determining step, is proposed.

Copper-Catalyzed Oxidation of Cyanide by Peroxide in Alkaline Aqueous Solution

1995 ◽  
Vol 48 (4) ◽  
pp. 861 ◽  
Author(s):  
JK Beattie ◽  
GA Polyblank
Keyword(s):  
Aqueous Solution ◽  
Copper Complexes ◽  
Final Concentration ◽  
First Order ◽  
Alkaline Aqueous Solution ◽  
Catalysed Oxidation ◽  
Complex Forms ◽  
Kinetics Of ◽  
Catalyzed Oxidation ◽  
Destructive Oxidation

The oxidation of cyanide by peroxide in alkaline aqueous solution is catalysed by copper complexes. In the presence of excess cyanide, copper(II) is reduced to form the tricyanocuprate (I) complex. The cyanogen oxidation product is hydrolysed with disproportionation to cyanate and cyanide:2CuII+2CN-→ 2CuI+(CN)2(CN)2+2OH- → OCN-+CN-+H2OCuI+3CN- ↔ Cu(CN)32-The stoichiometry and kinetics of the catalysed oxidation have been investigated. Hydrogen peroxide oxidizes coordinated cyanide with a rate that is first order in peroxide and first order in copper but independent of cyanide concentration in the presence of excess cyanide. Cu(CN)32-+H2O2→ Cu(CN)2-+OCN-+H2O Cu(CN)2-+CN-↔ Cu(CN)32- When the excess cyanide is consumed and Cu(CN)2- becomes the dominant species, the reaction becomes more complex and less efficient. Under certain conditions the stoichiometry revealed a peroxide-to-Cu(CN)2- ratio of about 6 : 1, instead of the minimum of 2.5:1 required for the oxidation of the coordinated cyanide to cyanate and the CuI to Cu(OH)2. This suggests that peroxide is consumed by a copper- catalysed disproportionation, in competition with oxidation of the coordinated cyanide. An intermediate yellow complex forms while peroxide is present, before Cu(OH)2 finally precipitates. The consequence of this mechanism is that the most efficient process for the destructive oxidation of cyanide has a high cyanide-to-copper ratio, to minimize the final concentration of Cu(CN)2- which consumes peroxide inefficiently. The rate of the reaction depends on the concentration of copper, however, which must be large enough for a satisfactory turnover.

Kinetics and Mechanism of Hexachloroiridate(IV) Oxidation of Arsenic(III) in Acidic Perchlorate Solutions

1992 ◽  
Vol 57 (7) ◽  
pp. 1451-1458 ◽  
Author(s):  
Refat M. Hassan
Keyword(s):  
Ionic Strength ◽  
Fractional Order ◽  
Activation Parameters ◽  
Order Reaction ◽  
First Order Reaction ◽  
Intermediate Complex ◽  
Constant Ionic Strength ◽  
Kinetics Of Oxidation ◽  
First Order ◽  
Kinetics Of

The kinetics of oxidation of arsenic(III) by hexachloroiridate(IV) at lower acid concentrations and at constant ionic strength of 1.0 mol dm-3 have been investigated spectrophotometrically. A first-order reaction in [IrCl62-] and fractional order with respect to arsenic(III) have been observed. A kinetic evidence for the formation of an intermediate complex between the hydrolyzed arsenic(III) species and the oxidant was presented. The results showed that decreasing the [H+] is accompanied by an appreciable acceleration of the rate of oxidation. The activation parameters have been evaluated and a mechanism consistent with the kinetic results was suggested.

Kinetics and mechanism of the reaction of iron(III) with 6-methyl-2,4-heptanedione and 3,5-heptanedione

1990 ◽  
Vol 55 (8) ◽  
pp. 1984-1990 ◽  
Author(s):  
José M. Hernando ◽  
Olimpio Montero ◽  
Carlos Blanco
Keyword(s):  
Aqueous Solution ◽  
Metal Ion ◽  
Activation Parameters ◽  
Enol Form ◽  
Kinetics And Mechanism ◽  
Kinetic Constants ◽  
Steric Factors ◽  
Kinetics Of ◽  
Mechanism Of The Reaction

The kinetics of the reactions of iron(III) with 6-methyl-2,4-heptanedione and 3,5-heptanedione to form the corresponding monocomplexes have been studied spectrophotometrically in the range 5 °C to 16 °C at I 25 mol l-1 in aqueous solution. In the proposed mechanism for the two complexes, the enol form reacts with the metal ion by parallel acid-independent and inverse-acid paths. The kinetic constants for both pathways have been calculated at five temperatures. Activation parameters have also been calculated. The results are consistent with an associative activation for Fe(H2O)63+ and dissociative activation for Fe(H2O)5(OH)2+. The differences in the results for the complexes of heptanediones studied are interpreted in terms of steric factors.

The mechanism of the oxidation of thiocyanate ion by peroxomonosulphate in aqueous solution. II. Kinetics of the reaction

1966 ◽  
Vol 19 (8) ◽  
pp. 1365 ◽  
Author(s):  
RH Smith ◽  
IR Wilson
Keyword(s):  
Aqueous Solution ◽  
Initial Rate ◽  
Stopped Flow ◽  
Thiocyanate Ion ◽  
First Order ◽  
Conductance Method ◽  
Rate Of Reaction ◽  
Kinetics Of

Initial rates of reaction for the above oxidation have been measured by a stopped-flow conductance method. Between pH 2 and 3.6, the initial rate of reaction, R, is given by the expression R{[HSO5-]+[SCN-]} = {kb+kc[H+]}[HSO5-]0[SCN-]20+ka[H+]-1[HSO5]20[SCN-]0 As pH increases, there is a transition to a pH-independent rate, first order in each thiocyanate and peroxomonosulphate concentrations.

scholarly journals EFFECT OF DIATOMEAOUS EARTH TREATMENT USING HYDROGEN CHLORIDE AND SULFURIC ACID ON KINETICS OF CADMIUM(II) ADSORPTION

2010 ◽  
Vol 2 (2) ◽  
pp. 107-112
Author(s):  
Nuryono Nuryono ◽  
Narsito Narsito
Keyword(s):  
Aqueous Solution ◽  
Sulfuric Acid ◽  
Hydrogen Chloride ◽  
Rate Constant ◽  
Diatomaceous Earth ◽  
Adsorption Rate ◽  
Physical Interaction ◽  
First Order ◽  
Adsorption Rate Constant ◽  
Kinetics Of

In this research, treatment of diatomaceous earth, Sangiran, Central Java using hydrogen chloride (HCl) and sulfuric acid (H2SO4) on kinetics of Cd(II) adsorption in aqueous solution has been carried out. The work was conducted by mixing an amount of grounded diatomaceous earth (200 mesh in size) with HCl or H2SO4 solution in various concentrations for two hours at temperature range of 100 - 150oC. The mixture was then filtered and washed with water until the filtrate pH is approximately 7 and then the residue was dried for four hours at a temperature of 70oC. The product was used as an adsorbent to adsorb Cd(II) in aqueous solution with various concentrations. The Cd(II) adsorbed was determined by analyzing the rest of Cd(II) in the solution using atomic absorption spectrophotometry. The effect of treatment was evaluated from kinetic parameter of adsorption rate constant calculated based on the simple kinetic model. Results showed  that before equilibrium condition reached, adsorpstion of Cd(II) occurred through two steps, i.e. a step tends to follow a reaction of irreversible first order  (step I) followed by reaction of reversible first order (step II). Treatment with acids, either hydrogen chloride or sulfuric acid, decreased adsorption rate constant for the step I from 15.2/min to a range of 6.4 - 9.4/min.  However, increasing concentration of acid (in a range of concentration investigated) did not give significant and constant change of adsorption rate constant. For step II process,  adsorption involved physical interaction with the sufficient low adsorption energy (in a range of 311.3 - 1001 J/mol).     Keywords: adsorption, cdmium, diatomaceous earth, kinetics.

scholarly journals Reactivity of Phenol and Aniline towards Quinolinium Chloro Chromate: A Comparative Oxidation Kinetic Study

2015 ◽  
Vol 59 ◽  
pp. 81-92
Author(s):  
Seplapatty Kalimuthu Periyasamy ◽  
H. Satham Hussain ◽  
R. Manikandan
Keyword(s):  
Oxidation Kinetic ◽  
Activation Parameters ◽  
Dipole Interaction ◽  
Reaction Rates ◽  
Hydrogen Ion ◽  
Aqueous Acetic Acid ◽  
Acetic Acid Medium ◽  
First Order ◽  
Different Temperatures ◽  
Kinetics Of

The kinetics of Oxidation of Phenol and aniline by quinolinium Chlorochromate (QCC) in aqueous acetic acid medium leads to the formation of quinone and azobenzene respectively. The reactions are first order with respect to both Phenol and aniline. The reaction is first order with respect to quinolinium chlorochromate (QCC) and is catalyzed by hydrogen ion. The hydrogen-ion dependence has the form: kobs = a+b [H+]. The rate of oxidation decreases with increasing dielectric constant of solvent, indicating the presence of an ion-dipole interaction. The reaction does not induced the polymerization of acrylonitrile. The retardation of the rate by the addition of Mn2+ ions confirms that a two electron transfer process is involved in the reaction. The reaction rates have been determined at different temperatures and the activation parameters have been calculated. From the above observations kinetic results a probable mechanism have been proposed.

Kinetics of the Reaction Between S2O3-- and I3- in Aqueous Solution

1974 ◽  
Vol 29 (1) ◽  
pp. 141-144
Author(s):  
T. S. Rao ◽  
S. I. Mali
Keyword(s):  
Aqueous Solution ◽  
Reduction Potential ◽  
Frequency Factor ◽  
Effective Concentration ◽  
Specific Rate ◽  
Platinum Foil ◽  
First Order ◽  
Entropy Of Activation ◽  
Kinetics Of ◽  
Foil Electrode

The kinetics of the reaction between has been studied under conditions of production of iodine at a known rate by the persulfate-iodide reaction and its consumption by S2O3-- . The effective concentration of iodine during the steady state is measured from its reduction potential at a bright platinum foil electrode. The reaction is of first order with respect to I3- and S2O3-- individually and hence of over all second order. The specific rate is 1.51 X 105 M -1 sec-1 and the frequency factor is 1.69 × 1012 M -1 sec-1 at 25 °C. The energy of activation for the reaction is 9.58 × 103 cal/mole and the entropy of activation is -2.55 cal/mole deg.

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