Abstract:
Kinetics and mechanism of the oxidation of thiophenol by ammonium trioxovana date (V), NH4VO3, was investigated in 40% (V/V) aqueous ethanol and 0.01 mol dm-3 HClO4. Vanadium(V) was reduced to the corresponding V(IV) whereas thiophenol was oxidized to diphenyldisulphide at 27 ˚C and I = 0.0101 mol dm-3 (NaClO4). Stoichiometric studies indicated that one mole of V(V) was reduced per mole of thiophenol oxidized. The reaction was determined to be first order in [oxidant] and [reductant]. The rate of reaction was positively affected on varying [H+] at 1 x 10-3 ≤ [H+] ≤ 0.1 mol dm-3. Plot of acid-dependant rate constants kH+ (k2) against the [H+]2 was linear without intercept. The rate of the reaction remained invariant on varying the ionic strength of the medium. Addition of small amounts of anions and cations did not affect the rate of reaction. The reaction has been rationalized on the basis of an inner-sphere reaction pathway.
