The kinetics of the oxidation of quinol by aquocobalt(III) ions in aqueous perchlorate media

Wells, Cecil F.; Kuritsyn, L. V.

doi:10.1039/j19690002930

Cited by 18 publications

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“…In the case of hydroquinone particularly, there is conflicting evidence as to the reaction mechanism. Davies (15) has suggested, from a comparison of reactivity of several substrates, that an outer-sphere process is operative but this conflicts with the data of Wells (16). Later investigations (14) support the former suggestion with no evidence for any reaction intermediates.…”

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confidence: 40%

Metal-ion oxidations in solution. Part XXI. Kinetics and mechanism of the reaction of ascorbic acid, hydroquinone, and catechol with 12-tungstocobaltoate(III)

Amjad¹,

Brodovitch²,

McAuley³

1977

Can. J. Chem.

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. Can. J. Chem. 55, 3581 (1977).The mechanisms of oxidation of the three di-hydroxy substrates in the title reactions have been investigated in acid media [HCIO,] = 0.04-1.00 M, at an ionic strength of 1.0 M [LiCIO,] over the temperature range 5-35°C using the stopped-flow method. In contrast to the reactions of hydroquinone (k2(25"C) = 1.43 x 10, M -' s-' , AH* = 3.6 + 0.4 kcal mol-I, AS* = -34 + 8 cal deg-' mol-') and catechol (k2(25"C) = 9.5 x 1 0 2 M -' s-', AH* = 5.9 _+ 0.9 kcal mol-', AS* = 27 + 8 cal deg-I mol-I) where no hydrogen ion dependence is observed over the range studied, the rate variations of oxidation of ascorbic acid (H2A) are consistent with two reactions involving H2A (k, = 77.4 M -' s-I, AH* = 4.5 , 0.6 kcal niol-', AS* = -35 + 5 cal deg-I mol-') and HA-( k , = 2.41 x lo5 M -' s-' , AH* = 2.0 + 1 kcal mol-', AS* = -17 + 6 cal deg-I mol-I). The dissociation constant of ascorbic acid has been redetermined over the temperature range studied. Solvation effects are considered important in these outer-sphere systems, which may be discussed in terms of the Marcus relationship. Comparisons with related reactions are discussed.

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confidence: 40%

Metal-ion oxidations in solution. Part XXI. Kinetics and mechanism of the reaction of ascorbic acid, hydroquinone, and catechol with 12-tungstocobaltoate(III)

Amjad¹,

Brodovitch²,

McAuley³

1977

Can. J. Chem.

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“…The reaction between H 2 Q and bromine is fast, and by comparing the experimental data and the simulation a value of 3 × 10 4 mol -1 dm 3 s -1 was obtained for k 16 . The order of k 16 is the same as the order of the rate constant of the reaction between H 2 Q and Fe(III), Co(III), Ce(IV), and Mn(III) 6 Absorbance changes during the bromate−1,4-dihydroxybenzene reaction.…”

Section: Resultsmentioning

confidence: 99%

“…The order of k 16 is the same as the order of the rate constant of the reaction between H 2 Q and Fe(III), Co(III), Ce(IV), and Mn-(III). 26 We assumed that by removing bromine the kinetics might become autocatalytic and therefore added CHD to the reaction mixture (Figure 7). At low CHD concentrations, the rate of reaction decreased, and at the end, an autocatalytic step appeared (curve b in Figure 7).…”

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confidence: 99%

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The 1,4-Cyclohexanedione−Bromate−Acid Oscillatory System. 3. Detailed Mechanism

Szalai

Kőrös

1998

J. Phys. Chem. A

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1,4-Cyclohexanedione (CHD) in its reaction with acidic bromate undergoes aromatization and one of the main resulting products 1,4-dihydroxybenzene (H2Q) is further oxidized and brominated to 1,4-benzoquinone and bromoorganics. The kinetics of H2Q formation, of the reaction of CHD and Br2, as well as of the reaction between H2Q and bromate ion, were followed spectrophotometrically. The latter reaction exhibited Landolt (clock)-type dynamics. On the basis of our earlier analytical and present kinetic investigations, a detailed mechanistic model has been suggested that could well simulate the temporal oscillations of the title system. H2Q plays an essential role in the mechanism and is responsible for the unusual behavior (200−300 oscillations) of this chemical oscillator. We pointed to the relation that may exist between the CHD−bromate−acid system and those reported as oscillatory Landolt-type reactions [e.g., I − S − Fe(CN ].

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“…The redox-reversible organic systems reacting with metal ion complexes were reported in earlier studies [12][13][14]. The oxidations of quinol, QH 2 , by Fe III [15][16][17][18], Co III [19][20][21][22], Ce IV [20], and Mn III [23,24], are all rapid reactions. Quinols have also been studied as reductants for IrCl 6 2- [25][26][27][28], V(V) [29], Np(VI) [30] and Mo(CN) 8 3- [31].…”

Section: Introductionmentioning

confidence: 87%

Kinetics of oxidation of benzenediols by (1,8-bis(2-hydroxyethyl)-1,3,6,8,10,13-hexaazacyclotetradecane)nickel(III) in aqueous acidic media

Anuradha

Vijayaraghavan

2010

Reac Kinet Mech Cat

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The kinetics of the oxidation of hydroquinone (H 2 Q), catechol (H 2 cat) and substituted catechols with nickel(III) macrocycle [NiL 1 ] 3? (L 1 = 1,8-bis(2-hydroxyethyl)-1,3,6,8,10,13-hexaazacyclotetradecane) has been studied spectrophotometrically in aqueous perchloric acid in the presence of sulfate. Over the pH range 1-2.6, and at higher sulfate concentration 0.05 \ [SO 42-] \ 0.2 mol dm -3 , the decomposition of [Ni III L 1 ] in the oxidation of benzenediols via [Ni III-L 1 (OH)(H 2 O)] is small. With hydroquinone, the rate constant is almost independent of the hydrogen ion concentration and with catechols, the involvement of catechol anion (Hcat -) has been considered. The rate constants for cross reactions are discussed in terms of the Marcus relationship.

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The kinetics of the oxidation of quinol by aquocobalt(III) ions in aqueous perchlorate media

Cited by 18 publications

References 0 publications

Metal-ion oxidations in solution. Part XXI. Kinetics and mechanism of the reaction of ascorbic acid, hydroquinone, and catechol with 12-tungstocobaltoate(III)

Metal-ion oxidations in solution. Part XXI. Kinetics and mechanism of the reaction of ascorbic acid, hydroquinone, and catechol with 12-tungstocobaltoate(III)

The 1,4-Cyclohexanedione−Bromate−Acid Oscillatory System. 3. Detailed Mechanism

Kinetics of oxidation of benzenediols by (1,8-bis(2-hydroxyethyl)-1,3,6,8,10,13-hexaazacyclotetradecane)nickel(III) in aqueous acidic media

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