Thursday , 29 June 2017

Kinetics and Oxidation Mechanism of Pentaamminecobalt (III) Complexes of α-Hydroxy Acids by Isoquinolinium Dichromate in Micellar Mmedia

Palanivela, P. Rajkumar*b and K. Subramanic
aDepartment of Chemistry, Government Arts College (Men) (Affiliated to Periyar University, Salem) Krishnagirii-635001, Tamilnadu, India.
bDepartment of Chemistry, Priyadarshini Engineering College (Affiliated to Anna University, Chennai), Vaniyambadi-635751, Vellore District, Tamilnadu, India.
cPG & Research Department of Chemistry, Islamiah College (Affiliated to Thiruvalluvar University, Vellore), Vaniyambadi-635752, Vellore District, Tamilnadu, India.

Isoquinolinium Dichromate (IQDC) is a new versatile reagent for selective oxidation of primary and secondary alcohols under mild conditions. It also oxidizes vicinal and nonvicinal diols to the corresponding α-hydroxy carbonyl compounds. The oxidation of pentaamminecobalt (III) complexes of α-hydroxy acids by Isoquinolinium Dichromate (IQDC) in micellar medium yielding nearly 100% of carbonyl compounds and 100% Co(II) are ultimate products.  In this reaction the rate of oxidation shows first order kinetics each in [Co(III)] and [IQDC].  The unbound   α-hydroxy acids yield about 100% of carbonyl compounds in presence of micelles.  The rate of oxidation of Co (III) complexes of both bound and unbound α- hydroxy acids are enhanced more in the presence of non-ionic micelle of Polysorbate 80, when compared to the anionic micelle of Sodium lauryl Ether Sulphate (NaLES) and cationic micelle of Benzethonium Chloride (BTCl).  The 1 mole of cobalt (III) complexes of α-hydroxy acids reacts with nearly 0.5 mole of IQDC, similarly 1 mole of  α-hydroxy acids reacts with nearly 1 mole of IQDC.   A mechanism consistent with kinetic data is proposed.

Keywords: Isoquinolinium Dichromate (IQDC), α-hydroxy acids, Micelles, Stoichiometry.

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