Stopped flow kinetics of Mn II catalysed Periodate Oxidation of o- Anisidine – First Report on Stability constant of the ternary Intermediate complex formation Jaspal Singh 1 , R. D. Kaushik* 1 , Om Singh 1 , Richa Saini 2 and Ekata Kumari 3 1 Department of Chemistry, Gurukul Kangri University, Haridwar (Uttarakhand) India 2 Department of Physics, Gurukul Kangri University, Haridwar (Uttarakhand) India 3 Uttaranchal College of Science and Technology, Dehradun (Uttarakhand), India Abstract: This paper is the first report on kinetic study and evaluation of stability constant of ternary complex forming in the Mn II - catalysed periodate oxidation of o-Anisidine (OA) in acetone-water medium. The formation of ternary intermediate unstable complex during the oxidation of aromatic amines by periodate ion catalysed by Mn II has been proposed in case of some anilines. Stop-flow spectrophotometric method was used to study the ternary complex formation and to determine its stability constant. The stop-flow trace shows the reaction to occur in two steps. The first step, which is presumably the formation of ternary complex, is relatively fast while the second stage is relatively quite slow. The stability constant evaluated for OA - Mn II - IO 4 - ternary complex by determining equilibrium absorbance is (2.73 ± 0 .15) × 10 6 . Kinetics of ternary complex formation was defined by the rate law (OA) under pseudo first order conditions. d[C 2 ]/dt = k obs ([C 2 ] eq -[C 2 ]) (A) or ln{[C 2 ] eq / ( [C 2 ] eq -[C 2 ])} = k obs . t (A) where, k obs is the pseudo first order rate constant, [C 2 ] is concentration of ternary complex at given time t, and [C 2 ] eq is the equilibrium concentration of ternary complex. Key words: Stopped flow kinetics, stability constant, ternary complex, Mn II catalysed, Periodate oxidation, o-anisidine. 1. Introduction Aromatic amines can come in contact with living organisms by inhalation, ingestion and skin contact and most of these are enlisted as carcinogenic and/ or toxic due to their genotoxic or cytotoxic properties 1, 2 . Aromatic amines are used as intermediates in the manufacture of plastics, dyes, drugs, explosives, rubber, epoxy polymers, azo dyes, aromatic polyurethane products and pesticides 3 . It is of interest to study their new reactions for understanding their role in physiological activities and for developing methods for their detection, estimation and treatment. Aromatic amines have been subjected to oxidation reactions by using oxidants like peroxydisulphate ion 4 and benzimidazolium fluorochromate 5 etc. The kinetics and mechanism of the uncatalysed and Mn II catalyzed non-Malapradian periodate oxidation of some aromatic amines has been the subject of study during the past few years. In these reports, a binary unstable intermediate complex formation between aromatic amine and periodate has been proposed in the reaction mechanism of uncatalysed reactions 6- 20 . Also, there are some reports available which propose the ternary complex formation between periodate, aromatic amine and Mn II in some reactions catalysed by Mn II 21-32 . In continuation to our studies on periodate International Journal of ChemTech Research CODEN (USA): IJCRGG, ISSN: 0974-4290, ISSN(Online):2455-9555 Vol.10 No.6, pp 228-240, 2017