Kinetics and mechanism of the oxidation of xanthates with iodine in aqueous solution

Publisher Website
Google Scholar
Abstract
The kinetics of the oxidation by iodine of ethyl xanthate to dixanthogen have been investigated in aqueous solution. The results can be simply interpreted in terms of a mechanism in which EtOCS2I is formed in an initial, very rapid reaction between iodine and xanthate. EtOCS2I then reacts at a measurable rate with a further mole of xanthate to give dixanthogen, with displacement of iodine. The mechanism may be summarized as in (i) and (ii) where the EtOCS2 –+ I2(I3 –) [graphic omitted] EtOCS2I + I–(2I–)(i), EtOCS2I + EtOCS2 – [graphic omitted] (EtOCS2)2+ I–(ii) equilibrium for reaction (i) lies far to the right, with an equilibrium constant K≥ 107(for reaction with I2). The second step has a rate constant k of 9.1 × 105 dm3 mol–1 s–1 at 25 °C. An increase in iodide concentration results in a decrease in the reaction rate. Evidence is presented to suggest that this results from the formation of an adduct (EtOCS2I2 –, stability constant K1 6.6 dm3 mol–1) between iodide and EtOCS2I, rather than from the reversal of equilibrium (i). The reaction rate is also reduced in the presence of acid, and this can be quantitatively accounted for in terms of the formation of ethyl hydrogen xanthate.

This publication has 0 references indexed in Scilit: