Abstract
Upon the addition of permanganate to a solution of thioacetamide, yellow-brown colour species appeared within the time of mixing, which was unstable in excess [thioacetamide]. At higher [thioacetamide] (≥2.0 × 10
−4
M dm
−3
), the formation and decomposition of yellow-brown colour were not observed. Experiments have been done to confirm the nature of that colour. Mn(IV) (water-soluble colloidal MnO
2
) and Mn(III) were formed as intermediates. Conventional transmission electron microscopic (TEM) and spectrophotometric techniques were used to determine the size of colloidal MnO
2
and oxidation rate of thioacetamide by MnO
2
, respectively. MnO
2
nanoparticles are spherical and are of uniform particle size, and the average particle size is ca. 25 nm. The influence of different parameters was measured, i.e. [reactants], [HClO
4
] and temperature. A comparison was made of the oxidation rates of different organic reductants (acetamide and thiourea) by permanganate. The order of the effectiveness was as follows: thioacetamide ≫ thiourea ≫ acetamide. The presence of electron-donating
-group and sulphur atom is responsible for the higher reactivity of thioacetamide which easily transfers the proton to
. The mechanism of the observed kinetics has been proposed and discussed.