Dramatic rate enhancements have been observed in the oxidation of acetone (MMK), ethyl methyl ketone (EMK), and isobutyl methyl ketone (IBMK) by N-bromosuccinimide (NBS) in the presence of a mixture of metal ions [Ru(III) + Ir(III)]. The rate of oxidation in the the [Ru(III) + Ir(III)] system is much faster than either in the Ru(III) or in Ir(III) catalyzed system. The order in [NBS] was found to be zero both in catalyzed as well as uncatalyzed reactions. However, the order in [ketone] changed from unity to a fractional one in metal ion catalyzed systems. On the basis of kinetic features, the most plausible mechanism involving the oxidation of [Ir(III)-ketone] by Ru(III) to give [Ir(V)-ketone] and Ru(I) in the rate limiting step is proposed. Ru(I) thus formed is oxidized by NBS to Ru(III) in a fast step is discussed and individual rate parameters were evaluated. 1. Introduction Bimetallic catalysts often exhibit improved properties than either of the single metal catalysts. This is generally called the synergistic effect. The presence of the synergistic activity of platinum and rhodium in bimetallic catalysts and possible reasons for the effects has been discussed in the literature [1–10]. The synergistic activity of certain mixed catalyst systems, namely, [Ag(I) + Mn(II)], [Ag(I) + Cu(II)], [Ru(III) + Mn(II)], [Ir(III) + Mn(II)] and [Ru(III) + Os(VIII)], and so forth, has been the subject of interest in the field of homogenous redox reactions by several workers [4–10] in recent years. N-bromosuccinimide (NBS) has been used as a versatile oxidizing agent and analytical reagent in acid and alkaline media [11–24]. In recent past microconcentrations (10？6 to 10？5？M) of Ru(III) and Ir(III) have been employed as an efficient catalyst in N-bromosuccinimide (NBS) oxidations and other redox systems [25–31]. Recently we have reported that Ru(III) 34 catalyzed the oxidation of aliphatic ketones by NBS in aqueous acetic acid [27], wherein trace amount of Ru(III) is used as a catalyst. However, kinetic studies involving the mixture of metal ions as a catalyst also appeared to be scanty in NBS oxidations. Preliminary experiments involving the mixture of Ru(III) and Ir(III) as a catalyst in NBS-aliphatic ketone redox system in aqueous acetic acid medium containing H2SO4 indicated that the reaction rate is much greater than the sum of the reaction rates when metal ions such as Ru(III) and Ir(III) are separately employed as a catalyst. These striking features have become stimulus for us to take up a systematic kinetic study comprising the catalytic oxidation of certain
References
[1]
K. C. Taylor, “Automobile catalytic converters,” in Catalysis: Science and Technology, J. R. Anderson and M. Boudart, Eds., vol. 5, pp. 119–170, Springer, Berlin, Germany, 1984.
[2]
K. C. Taylor, “Nitric oxide catalysis in automotive exhaust systems,” Catalysis Reviews: Science and Engineering, vol. 35, no. 4, pp. 457–481, 1993.
[3]
A. Gayen, T. Baidya, K. Biswas, S. Roy, and M. S. Hegde, “Synthesis, structure and three way catalytic activity of Ce1？xPtx/2Rhx/2O2？δ (x = 0.01 and 0.02) nano-crystallites: synergistic effect in bimetal ionic catalysts,” Applied Catalysis A, vol. 315, pp. 135–146, 2006.
[4]
W. H. McCurdy Jr. and G. G. Guilbault, “Catalysts for cerium(IV) oxidimetry: determination of mixtures of mercury(I) and mercury(II),” Analytical Chemistry, vol. 32, no. 6, pp. 647–650, 1960.
[5]
G. G. Guilbault and W. H. McCurdy Jr. Jr., “Catalysts for cerium(IV) oxidimetry: determination of polyhydric alcohols and metal chelates of 8-quinolinol,” Analytical Chemistry, vol. 33, no. 4, pp. 580–582, 1961.
[6]
G. G. Guilbault and W. McCurdy Jr., “Determination of phosphite, hypophosphite, tellurium and mercury,” Analytica Chimica Acta, vol. 24, pp. 214–218, 1961.
[7]
P. K. Saiprakash, B. Sethuram, and T. N. Rao, “(Ag+ + Mn2+)–catalysed oxidation of isopropanol by ceric sulphate,” Indian Journal of Chemistry A, vol. 14, p. 701, 1976.
[8]
Y. Ramananda Sarma, Kinetic study of redox reactions with one electron Oxidants [Ph.D. thesis], Osmania University, Andhra Pradesh, India, 1987.
[9]
Y. R. Sarma, K. C. Rajanna, and P. K. Sai Prakash, “Kinetics of Ru(III) + Mn(III) nd Mn (III)catalysed oxidative decarboxylation of acetic and phenyl acetic acids by ceric sulphate,” Indian Journal of Chemistry A, vol. 19, p. 825, 1980.
[10]
Y. R. Sarma and P. K. Saiprakash, “Kinetics of Ir (III) # Ir(III) + Mn(II) catalysed oxidative decarboxylation and deamination of glycine, glutamic acid and serine by Ce(IV) in H2SO4media,” Indian Journal of Chemistry A, vol. 19, p. 1139, 1980.
[11]
R. Filler, “Oxidations and dehydrogenations with N-bromosuccinimide and related N-haloimides,” Chemical Reviews, vol. 63, pp. 21–43, 1963.
[12]
N. K. Mathur and C. K. Narang, The Determination of Organic Compounds with NBS and Allied Reagents, Acadamic Press, New York, NY, USA, 1975.
[13]
D. L. Kamble, G. H. Hugar, and S. T. Nandibewoor, “Kinetics of oxidation of chromium(III) by N-bromosuccinimide in aqueous alkaline medium,” Indian Journal of Chemistry A, vol. 35, no. 2, pp. 144–147, 1996.
[14]
D. L. Kamble, R. B. Chougale, and S. T. Nandibewoor, “Kinetics and mechanism of uncatalyzed and ruthenium(III) catalyzed oxidation of allyl alcohol by N-bromosuccinimide in aqueous alkaline medium,” Indian Journal of Chemistry A, vol. 35, no. 10, pp. 865–869, 1996.
[15]
P. Saroja, B. K. Kumar, and S. Kandlikar, “Kinetic and mechanism of uncatalyzed and Ir (III) catalyzed oxidation of oxalate ion by N-bromosuccinimide in basic medium,” Indian Journal of Chemistry A, vol. 28, p. 501, 1989.
[16]
S. K. Mavalangi, M. R. Kembhavi, and S. T. Nandibewoor, “Oxidation of ethylenediaminetetraacetic acid by N-bromosuccinimide in aqueous alkaline medium—a kinetic study,” Turkish Journal of Chemistry, vol. 25, no. 3, pp. 355–363, 2001.
[17]
S. Gunasekaran and N. Venkatasubramanian, “Oxidation of diphenylmethanol by bromamine T. A kinetic and mechanistic study,” Journal of the Chemical Society, Perkin Transactions 2, no. 7, pp. 949–953, 1983.
[18]
J. P. Sharma, R. N. P. Singh, A. K. Singh, and B. Singh, “Kinetics and mechanism of Ru(III) catalysed oxidation of some polyhydric alcohols by N-bromosuccinimide in acidic media,” Tetrahedron, vol. 42, no. 10, pp. 2739–2747, 1986.
[19]
R. Ramachandrappa, Puttaswamy, S. M. Mayanna, and N. M. M. Gowda, “Kinetics and mechanism of oxidation of aspirin by bromamine-T, N-bromosuccinimide, and N-bromophthalimide,” International Journal of Chemical Kinetics, vol. 30, no. 6, pp. 407–414, 1998.
[20]
A. L. Harihar, M. R. Kembhavi, and S. T. Nandibewoor, “Kinetics and mechanism of N-bromosuccinimide oxidation of L-arginine in aqueous acidic medium,” Journal of the Indian Chemical Society, vol. 76, no. 3, pp. 128–130, 1999.
[21]
A. K. Singh, S. Rahmani, V. K. Singh, V. Gupta, D. Kesarwani, and B. Singh, “Iridium (III) catalysis of N-bromosuccinimide oxidation of reducing sugars in aqueous acid,” Indian Journal of Chemistry A, vol. 40, no. 5, pp. 519–523, 2001.
[22]
C. Karunakaran and K. Ganapathy, “Kinetic study on the reaction of N-bromosuccinimide with β, γ-unsaturated alcohols in aqueous acetic acid,” Indian Journal of Chemistry A, vol. 29, p. 133, 1990.
[23]
N. Venkatasubramanian and V. Thiagarajan, “Mechanism of oxidation of alcohols with N-bromo succinimide,” Canadian Journal of Chemistry, vol. 47, no. 4, pp. 694–697, 1969.
[24]
N. A. M. Farook, “Kinetics and mechanism of oxidation of 4-oxoacids by N-bromosuccinimide in aqueous acetic acid medium,” Journal of the Iranian Chemical Society, vol. 3, no. 4, pp. 378–386, 2006.
[25]
P. G. Reddy, Y. Ramesh, and S. Kandlikar, “Ru (III) catalyzed oxidation of ethanolamine, diethanolamine and tri ethanolamine by N-bromosuccinimide—a kinetic study,” Oxidation Communications, vol. 7, p. 89, 1984.
[26]
P. G. Reddy, A. V. Reddy, A. Ratnamala, S. V. Rao, and S. Kandlikar, “Ru(III) catalyzed oxidation of some aliphatic alcohols by N-bromosuccinimide (NBS). A kinetic study,” Reaction Kinetics and Catalysis Letters, vol. 26, no. 1-2, pp. 209–213, 1984.
[27]
P. G. Reddy, K. Ramesh, S. Shylaja, K. C. Rajanna, and S. Kandlikar, “Ru (III) catalyzed oxidation of aliphatic ketones by N-bromosuccinimide in aqueous acetic acid: a kinetic study,” The Scientific World Journal, vol. 2012, Article ID 456516, 7 pages, 2012.
[28]
K. N. Shivananda, B. Lakshmi, R. V. Jagadeesh, Puttaswamy, and K. N. Mahendra, “Mechanistic studies on the Ru(III)-catalyzed oxidation of some aromatic primary diamines by chloramine-T in hydrochloric acid medium: a kinetic approach,” Applied Catalysis A, vol. 326, no. 2, pp. 202–212, 2007.
[29]
K. N. Shivananda, R. V. Jagadeesh, Puttaswamy, and K. N. Mahendra, “Ru(III)-catalysed oxidation of some amines by chloramine-T in hydrochloric acid medium: mechanistic aspects and kinetic modeling,” Journal of Molecular Catalysis A, vol. 255, no. 1-2, pp. 159–170, 2006.
[30]
G. Caroling, J. Rajaram, and J. C. Kuriacose, “Kinetics and mechanism of Ru(III)-catalysed oxidation of organic sulphides and triphenylphosphine by N-methylmorpholine N-oxide,” Proceedings of the Indian Academy of Sciences, vol. 100, no. 1, pp. 13–20, 1988.
[31]
M. D. P. Rao, M. Ahmad, P. K. Pujapanda, and T. K. Kanungo, “Ru(III)-catalyzed oxidation of acetanilide, o-chloroacetanilide, p-chloroacetanilide and p-methylacetanilide by sodium perioda'te at pH4,” Reaction Kinetics and Catalysis Letters, vol. 26, no. 3-4, pp. 375–379, 1984.
