Abstract
Two colored extinction bands, one with λmax near 520 nm and the other near 770 nm, form and decay during air oxidations of 4,6-di(2-phenyl-2-propyl) pyrogallol in alkaline methanol. The 770 nm band appears to be due to the semiquinone monoanion while the extinction near 500 nm is thought to be due to both the semiquinone and 3-hydroxy-o-quinone. Although the rates of formation and decay of the two bands are indistinguishable in the presence of excess dissolved oxygen, the 770 nm band disappears slightly before the 500 nm extinction when the pyrogallol reactant is initially in excess of the dissolved oxygen. Except at high methoxide concentrations, the kinetics indicate a system of two consecutive reactions with pseudo first-order rate constants k1 and k2. The pH′ dependence of k1 indicates that the neutral pyrogallol, its monoanion and dianion all react, the rate increasing with the negative charge of the species. The k2/k1 ratio is constant at 5 from pH′ 11 to 16. Extinction coefficients at both wavelengths increase with pH′. The 770 nm extinction disappears immediately after acidification while the 500 nm extinction decays at a rate consistent with oxidation. The rate constants k1 and k2 are insensitive to changes in pyrogallol concentrations, indicating an absence of irreversible semiquinone disproportionations. Increased oxygen concentration raises k1 and k2 to the same extent.
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Abichandani, C. T. &S. K. K. Jatkar: Dissociation constants ofo-,m- andp-hydroxybenzoic acids, gallic acid, catechol, resorcinol, hydroquinone, pyrogallol and phloroglucinol. J. Indian Inst. Sci. 21A, 4.7–441 (1938)
Abrash, H. I. &C. Niemann: Steric hindrance in α-chymotrypsin-catalyzed reaction. Biochemistry, 2, 847–853 (1963)
Alcock, N. W., D. J. Benton &P. Moore: Kinetics of series first-order reactions. Analysis of spectrophotometric data by the method of least squares and an ambiguity. Trans. Faraday Soc. 66, 2210–2213 (1970)
Auld, D. S. &T. C. French: Cell for spectrophotometric titrations with small volumes. Anal. Biochem. 34, 262–274 (1970)
Bates, R. G.: Determination of pH. Theory and Practice, John Wiley & Sons (New York) pp. 222–229 (1964)
ibid., p. 183.
ibid. pp. 151–152.
Broser, W. &H. Fleischauer: Substituent-effekte bei Triphenylmethanfarbstoffen II. Eine Pufferreihe für das methanolische Medium. Z. Naturforsch. 25b, 1389–1394 (1970)
Campbell, T. W.: The oxidation of di-t-butylpyrogallol by oxygen in alkaline solution. J. Am. Chem. Soc. 73, 4190–4195 (1951)
Doskocil, J.: Polarography of some orthophenols and their oxidation products. Collect. Czechoslov. Chem. Commun. 15, 599–613 (1950)
Frost, A. A. &R. G. Pearson: Kinetics and Mechanism, John Wiley & Sons (New York) p. 155 (1953)
Harries, C.: Ueber die Autoxydation des Pyrogallos. Chem. Ber. 35, 2954–2959 (1902)
Hathway, D. E.: Autoxidation of polyphenols. I. Autoxidation of methyl gallate and its O-methyl ethers in aqueous ammonia. J. Chem. Soc. 519–523 (1957)
Hoskins, R. H. &B. R. Loy: Paramagnetic resonance in solutions of oxidized pyrogallol. J. Chem. Phys. 23, 2461–2462 (1955)
Washburn, E. W., ed.: International Critical Tables of Numerical Data. Physics, Chemistry and Technology, McGraw-Hill (New York) Volume III p. 262 (1928)
Jönsson, Á: Studies on Antimetabolites. I. Synthesis D,L-«neophenylalanine», D,L-«neotyrosine» and D,L-«neo-3,5-diiodo-tyrosine, the β, β-dimethyl analogues of optically inactive phenylalanine, tyrosine and 3,5-diiodotyrosine. Acta Chem. Scand. 8, 1203–1210 (1954)
Marklund, S. &G. Marklund: Involvement of the superoxide anion radical in the autoxidation of pyrogallol and a convenient assay for superoxide dismutase. Eur. J. Biochem. 47, 469–474 (1974)
Meluzova, G. B. &R. F. Vassilev: Stoichiometry of chemiluminescent oxidation of pyrogallol by oxygen in aqueous solutions. Mol. Photochem. 2, 251–257 (1970)
Nierenstein, M.: An oxidation product of pyrogallol. J. Chem. Soc. 107, 1217–1220 (1915)
Nilsson, R.: On the mechanism of peroxidase catalyzed oxidations studied by means of chemiluminescence measurements. Acta Chem. Scand. 18, 389–401 (1964)
Nishinaga, A., T. Ithara &T. Matsuura: Base catalyzed oxygenation of 3,5-di-t-butylpyrocatechol and its related compounds. Bull. Chem. Soc. Japan 47, 1811–1812 (1974)
Rein, H. &O. Ristau: Elektronenspinresonanz-Untersuchungen über die Oxydationskinetik von Phenylverbindungen. 1. Mitteilung: Die Kinetik der Radialbildung bei der Oxydation des Pyrogallols. Z. Phys. Chem. (Leipzig) 239, 115–123 (1968)
Salfeld, J.-C.: Über die Oxydation von Pyrogallol und Pyrogallolderivaten, II, Die Konstitution dimerer 3-Hydroxy-o-benzochinone. Chem. Ber. 93, 737–745 (1960)
Schulze, H. &W. Flaig: Zur Kenntnis der Huminsaüren IV, Mitteilung Über die Ringsprengung mehrwertiger Phenole mit Sauerstoff in alkalischem Medium Ann. 575, 231–241 (1952)
Tabagua, I. S.: Dissociation constants of some acids in methanol and its mixtures with water. Tr. Sukhumsk. Gos. Ped. Inst. 15; 119–133. Ref. Chem. Abstracts 60, 14373d (1964)
Talat-Erben, M.: Displacement of the maximum in the concentration-time diagram of uni-bi, bi- uni, and bi-bimolecular consecutive reactions. J. Chem. Phys. 26, 75–77 (1957)
Taube, H.: Mechanism of oxidations with O. J. Gen. Physiol. 49 Pt. 2, 29–50 (1965)
Vartanyan, L. S., L. M. Strigun &N. M. Emanuel: Kinetics of the autoxidation of propyl gallate in aqueous solution. Dokl. Akad. Nauk. SSSR. 148, 97–100 (1963)
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Current address: Department of Chemistry, California State University at Northridge Northridge, California 91324, USA
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Abrash, H.I. The air oxidation of 4,6-di (2-phenyl-2-propyl) pyrogallol. Spectroscopic and kinetic studies of the intermediates. Carlsberg Res. Commun. 42, 11–25 (1977). https://doi.org/10.1007/BF02906706
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DOI: https://doi.org/10.1007/BF02906706