메뉴 건너뛰기




Volumn 129, Issue 42, 2007, Pages 12847-12856

Voltammetry of quinones in unbuffered aqueous solution: Reassessing the roles of proton transfer and hydrogen bonding in the aqueous electrochemistry of quinones

Author keywords

[No Author keywords available]

Indexed keywords

CYCLIC VOLTAMMETRY; HYDROGEN BONDS; PH EFFECTS; PROTON TRANSFER; REDOX REACTIONS; SOLUTIONS;

EID: 35449008481     PISSN: 00027863     EISSN: None     Source Type: Journal    
DOI: 10.1021/ja0743083     Document Type: Article
Times cited : (507)

References (67)
  • 4
    • 0004122931 scopus 로고    scopus 로고
    • 3rd ed, Thomson Brooks/ Cole: Belmont, CA
    • Garrett, R. H.; Grisham, C. M. Biochemistry, 3rd ed.; Thomson Brooks/ Cole: Belmont, CA, 2005; pp 681-685.
    • (2005) Biochemistry , pp. 681-685
    • Garrett, R.H.1    Grisham, C.M.2
  • 5
    • 35549008010 scopus 로고    scopus 로고
    • Reference 4, pp 645-657
    • Reference 4, pp 645-657.
  • 6
    • 35548929356 scopus 로고    scopus 로고
    • 5th ed, Seidel, A, Ed, John Wiley & Sons: Hoboken, NJ
    • Hattori, M. In Kirk-Othmer Encyclopedia of Chemical Technology, 5th ed.; Seidel, A., Ed.; John Wiley & Sons: Hoboken, NJ, 2004; Vol. 9, pp 300-349.
    • (2004) Kirk-Othmer Encyclopedia of Chemical Technology , vol.9 , pp. 300-349
    • Hattori, M.1
  • 7
    • 35548930692 scopus 로고    scopus 로고
    • A particularly significant industrial use of quinones is as the hydrogen carrier in the production of hydrogen peroxide: Eul, M.; Moeller, A.; Steiner, N. In Kirk-Othmer Encyclopedia of Chemical Technology, 5th ed.; Seidel, A., Ed.; John Wiley & Sons: Hoboken, NJ, 2004; 14, pp 42-51.
    • A particularly significant industrial use of quinones is as the "hydrogen carrier" in the production of hydrogen peroxide: Eul, M.; Moeller, A.; Steiner, N. In Kirk-Othmer Encyclopedia of Chemical Technology, 5th ed.; Seidel, A., Ed.; John Wiley & Sons: Hoboken, NJ, 2004; Vol. 14, pp 42-51.
  • 8
    • 35548992329 scopus 로고    scopus 로고
    • Quinones are most commonly used as mild oxidizing agents and as dehydrogenating reagents, particularly for aromatization: Finley, K. T. In Kirk-Othmer Encyclopedia of Chemical Technology, 5th ed.; Seidel, A., Ed.; John Wiley & Sons: Hoboken, NJ, 2004; 21, pp 238-270.
    • Quinones are most commonly used as mild oxidizing agents and as dehydrogenating reagents, particularly for aromatization: Finley, K. T. In Kirk-Othmer Encyclopedia of Chemical Technology, 5th ed.; Seidel, A., Ed.; John Wiley & Sons: Hoboken, NJ, 2004; Vol. 21, pp 238-270.
  • 9
    • 7444256681 scopus 로고    scopus 로고
    • See the following for leading references on some quinones with medicinal activity
    • See the following for leading references on some quinones with medicinal activity: Bautista-Martinez, J. A.; Gonzalez, I.; Aguilar-Martinez, M. J. Electroanal. Chem. 2004, 573, 289-298.
    • (2004) J. Electroanal. Chem , vol.573 , pp. 289-298
    • Bautista-Martinez, J.A.1    Gonzalez, I.2    Aguilar-Martinez, M.3
  • 23
    • 35548932433 scopus 로고    scopus 로고
    • This argument is nicely expressed by Bailey and Ritchie in their 1985 paper, ref 16, but it goes back much further, at least to Muller's 1940 paper, ref 13
    • This argument is nicely expressed by Bailey and Ritchie in their 1985 paper, ref 16, but it goes back much further, at least to Muller's 1940 paper, ref 13.
  • 25
    • 27744499477 scopus 로고    scopus 로고
    • Studies like this are rare with organic redox couples, but there are more examples with inorganic couples. A very nice recent example is the following study by Bond, Weld and co-workers looking at the redox chemistry of an iron-substituted polyoxotungstate: Guo, S.-X, Feldberg, S. W, Bond, A. M, Callahan, D. L, Richardt, P. J. S, Wedd, A. G. J. Phys. Chem. B 2005, 109, 20641-20651. This study also demonstrates that, in addition to understanding solvent effects, studies in unbuffered solution can also be useful for sorting out mechanistic details. This is because the distribution of intermediates and products will be different in the absence of buffer, making the voltammetry sensitive to different parameters. In the above paper, digital simulation of the CVs in the unbuffered solution allowed determination of parameters that the studies in the buffered solutions could only place an upper limit on
    • Studies like this are rare with organic redox couples, but there are more examples with inorganic couples. A very nice recent example is the following study by Bond, Weld and co-workers looking at the redox chemistry of an iron-substituted polyoxotungstate: Guo, S.-X.; Feldberg, S. W.; Bond, A. M.; Callahan, D. L.; Richardt, P. J. S.; Wedd, A. G. J. Phys. Chem. B 2005, 109, 20641-20651. This study also demonstrates that, in addition to understanding solvent effects, studies in unbuffered solution can also be useful for sorting out mechanistic details. This is because the distribution of intermediates and products will be different in the absence of buffer, making the voltammetry sensitive to different parameters. In the above paper, digital simulation of the CVs in the unbuffered solution allowed determination of parameters that the studies in the buffered solutions could only place an upper limit on.
  • 26
    • 0001495195 scopus 로고    scopus 로고
    • The peak potentials varied slightly from experiment to experiment almost certainly due to variations in the condition of the glassy carbon surface. It is known that the rates of quinone reduction in water are very sensitive to the condition of the electrode surface: White, J. H, Soriaga, M. P, Hubbard, A. T. J. Electroanal. Chem. 1985, 185, 331-8
    • The peak potentials varied slightly from experiment to experiment almost certainly due to variations in the condition of the glassy carbon surface. It is known that the rates of quinone reduction in water are very sensitive to the condition of the electrode surface: White, J. H.; Soriaga, M. P.; Hubbard, A. T. J. Electroanal. Chem. 1985, 185, 331-8.
  • 27
    • 35548946619 scopus 로고    scopus 로고
    • Strong support for an overall 2 e- process comes from some of the other studies of benzoquinone in unbuffered aqueous solution in which steady-state voltammograms were produced. For example, in Müller's 1940 Polarographic study (ref 13) in which the concentration of buffer was varied, the maximum limiting current was the same at all buffer concentrations, indicating that the same number of electrons were involved. Robertson and Pendley (ref. 17) observed 54 years later similar behavior and came to the same conclusion when they measured the steady-state voltammograms of BQ in the presence of small concentrations of sulfuric acid with 5 micron diameter Pt microelectrodes. In addition, although they do not actually show the data, Wang and co-workers (ref 21) state that they confirmed that the reaction was 2 e, using a rotating disk electrode, another steady-state technique
    • - using a rotating disk electrode, another steady-state technique.
  • 28
    • 35548996265 scopus 로고    scopus 로고
    • It is interesting to note that only the two waves are observed in this experiment; there is no intermediate CV wave corresponding to BQH, This behavior is consistent with rapid protonation equilibria. Although BQH, will be the major species produced with 1 equiv of OH, small amounts of the other protonation states have to also be present at equilibrium. Since Q2- will be the easiest to oxidize, it is oxidized first. This removes these ions from the mixture, causing some of the QH, to dissociate to Q2- and H+ in order to re-establish equilibrium. This Q2- is then oxidized, more QH, dissociates, and so on, until half of the original QH- has been oxidized and half an equivalent of H+ has been produced. These H+'s will have combined with the remaining QH- to make QH2 which is oxidized at the more positive potential
    • 2 which is oxidized at the more positive potential.
  • 33
    • 35548987955 scopus 로고    scopus 로고
    • The nonlinear least squares regression fit was accomplished using the Levenberg-Marquardt method as implemented in PsiPlot V 8.11
    • The nonlinear least squares regression fit was accomplished using the Levenberg-Marquardt method as implemented in PsiPlot V 8.11.
  • 34
    • 35548949796 scopus 로고    scopus 로고
    • It should be noted that there is an error in pKa values measured in this fashion introduced by combining voltammetric E 1/2 values with Potentiometric pH values those measured with a pH electrode, The former are inherently concentration sensitive due to their dependence on a current measurement, whereas the latter are inherently activity dependent. Equation 1 is rigorously correct with formal potentials and proton concentrations. The problem is simply that we are actually measuring proton activity. However, if the ionic strength is constant, the error in the pH should be constant and equal to log of the activity coefficient for protons at the ionic strength used. For this work, the error is essentially self-correcting because our main use of these pKa values is to calculate the expected E1/2 in unbuffered solution as a function of the activity dependent pH's
    • 1/2 in unbuffered solution as a function of the activity dependent pH's.
  • 35
    • 35548997138 scopus 로고    scopus 로고
    • a2: 9.28 (ref 29), 10.9 (I = 1, ref 16), 11.05 (I = 0.1, ref 30), 11.05 (30°C, I = 0.2, ref 31), 11.08 (Broadbent and Melanson), 11.3 (ref 32).
    • a2: 9.28 (ref 29), 10.9 (I = 1, ref 16), 11.05 (I = 0.1, ref 30), 11.05 (30°C, I = 0.2, ref 31), 11.08 (Broadbent and Melanson), 11.3 (ref 32).
  • 36
    • 35548981709 scopus 로고    scopus 로고
    • The complete derivation of eqs 5 and 6 are given in the Supporting Information.
    • The complete derivation of eqs 5 and 6 are given in the Supporting Information.
  • 37
    • 35548935596 scopus 로고    scopus 로고
    • - at the electrode follows the same logic as that used for eq 6, except because of the second base dissociation, a quartic (fourth order) equation results instead of a quadratic. The exact equations along with an outline of their derivation are given in the Supporting Information.
    • - at the electrode follows the same logic as that used for eq 6, except because of the second base dissociation, a quartic (fourth order) equation results instead of a quadratic. The exact equations along with an outline of their derivation are given in the Supporting Information.
  • 40
    • 0007184057 scopus 로고    scopus 로고
    • a's at I = 0.65: Baxendale, J. H.; Hardy, H. R. Trans. Faraday Soc. 1953, 49, 1140-4.
    • a's at I = 0.65: Baxendale, J. H.; Hardy, H. R. Trans. Faraday Soc. 1953, 49, 1140-4.
  • 41
    • 35548937804 scopus 로고    scopus 로고
    • The pH and % distributions were calculated using the spreadsheet program described in the following: Fresier, H. Concepts & Calculations in Analytical Chemistry, A Spreadsheet Approach; CRC Press: Ann Arbor, MI, 1992; Chapter 4.
    • The pH and % distributions were calculated using the spreadsheet program described in the following: Fresier, H. Concepts & Calculations in Analytical Chemistry, A Spreadsheet Approach; CRC Press: Ann Arbor, MI, 1992; Chapter 4.
  • 47
    • 35548941356 scopus 로고    scopus 로고
    • + transfer reaction, which Laviron's theory does not consider. There is much current interest in such reactions, but we are not aware of any evidence presented so far that they are involved in aqueous quinone redox chemistry.
    • + transfer reaction, which Laviron's theory does not consider. There is much current interest in such reactions, but we are not aware of any evidence presented so far that they are involved in aqueous quinone redox chemistry.
  • 48
    • 35548997408 scopus 로고    scopus 로고
    • This is the mechanism originally proposed by Vetter based on analysis of Tafel plots for BQ/BQH2 at different pH's: Vetter, K. J. Z. Elektrochem. 1952, 56, 797-806. Other workers disputed this mechanism; see ref 1 for a summary. However, Laviron (ref 39) re-examined Vetter's data based on his theory and came to the same conclusion as Vetter for neutral pH
    • 2 at different pH's: Vetter, K. J. Z. Elektrochem. 1952, 56, 797-806. Other workers disputed this mechanism; see ref 1 for a summary. However, Laviron (ref 39) re-examined Vetter's data based on his theory and came to the same conclusion as Vetter for neutral pH.
  • 49
    • 35548960446 scopus 로고    scopus 로고
    • This concept was originally proposed by Hoijtink for aromatic radical anions based on Huckel-type molecular orbital calculations: Hoitjink, G. J, van Schooten, J, de Boer, E, Aalbersberg, W. Y. Recl. Trav. Chim. 1954, 73, 355-375
    • This concept was originally proposed by Hoijtink for aromatic radical anions based on Huckel-type molecular orbital calculations: Hoitjink, G. J.; van Schooten, J.; de Boer, E.; Aalbersberg, W. Y. Recl. Trav. Chim. 1954, 73, 355-375.
  • 50
    • 0001312964 scopus 로고
    • It has long been recognized to be true for quinone radical anions as well; see
    • It has long been recognized to be true for quinone radical anions as well; see: Peover, M. E. Electroanal. Chem. 1967, 2, 1-51.
    • (1967) Electroanal. Chem , vol.2 , pp. 1-51
    • Peover, M.E.1
  • 51
    • 33644765142 scopus 로고    scopus 로고
    • Recent high level computations support the conclusion that the QH radical will be an unstable intermediate in the Q to QH2 conversion in both the gas phase and water: Johnsson Wass, J. R. T, Ahlberg, E, Panas, I, Schiffrin, D. J. J. Phys. Chem. A 2006, 110, 2005-2020
    • 2 conversion in both the gas phase and water: Johnsson Wass, J. R. T.; Ahlberg, E.; Panas, I.; Schiffrin, D. J. J. Phys. Chem. A 2006, 110, 2005-2020.


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.