Kinetic evidence for the copper peroxide intermediate with two copper ions in proximity

• Published in: International journal of chemical kinetics 2006-07, Vol.38 (7), p.439-443
• Main Authors: Selvarani, S., Medona, B., Ramachandran, M. S.
• Format: Article
• Language: English
• ISSN: 0538-8066; 1097-4601
• DOI: 10.1002/kin.20168

The decomposition of caroate (peroxomonosulfate, PMS) is catalyzed by Cu(II) ions even at 5 × 10−5 M in aqueous alkaline solution. The rate is second order in copper(II) ions concentrations and first order in [PMS]. The rate constant values are found to decrease with increase in hydroxide ion concentrations. The turnover number for the reaction is estimated as >1000. The experimental results suggest that the formation of peroxide type intermediate with two copper(II) ions is the rate‐determining step. This peroxide intermediate reacts with another molecule of PMS to give the products oxygen, SO 2−4 and copper ions. The overall entropy of activation is positive with a value of ∼20 cals/mol/K. The very high turnover number suggests that Cu(II) ion is one of the best catalysts for the decomposition of caroate ions in alkaline medium. The reaction also represents a system in which metal ion catalyzed decomposition of caroate does not involve radical intermediates. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 439–443, 2006