Micellar Catalysed Kinetic Oxidation Study of Acetophenone by N-Bromosaccharin in Aqueous Acetic Acid Medium

Abstract

The kinetic oxidation study of acetophenone by N-bromosaccharin in aqueous acetic acid medium and in presence of Hg(II) acetate was investigated in the presence of both cationic and anionic micelles. The reaction obeys first order kinetics in oxidant both in the presence as well as absence of micelle. The kinetic results for dependence on substrate concentration indicate intermediate complex formation between oxidant and substrate species. The reactions are acid catalysed and follow both acid dependent and independent path. Change in polarity of the medium, effect of addition of saccharin and Hg(II) acetate have also been investigated. Both type of micelles catalyses the oxidation. Binding parameters have been calculated by analyzing the data using the model suggested by Piszkiewicz. On the basis of kinetic results probable mechanism is proposed. ExperimentalN-Bromosaccharin was prepared by the method suggested by Bacchawat and Mathur 11 and was standardized by iodometric method 12 . Acetophenone (Rhone-Poulene, b.p. 202 °C) solution was prepared by dissolving in glacial acetic acid. The solution of cetyltrimethylammonium bromide (CTAB)-cationic surfactant and sodium lauryl sulphate RESEARCH ARTICLEChem Sci Trans., 2015, 4(4), 890-896 891 (NaLS)-anionic surfactant was prepared by dissolving their appropriate amount in distilled water. Acetic acid (Sd.fine SDS) was first refluxed with chromium trioxide (20 g) and acetic anhydride (20 mL) for 3 h using air condenser. Then it is distilled above 110 °C and distillate was collected. This distillate was used in kinetic studies. Kinetic measurementsKinetic studies were carried out using Ostwald's isolation method. The reaction mixture was equilibrated in a thermosat (±0.1 °C) at desired temperature. The progress of the reaction was monitored by iodometric estimation of unreacted N-bromosaccharin. Stoichiometry and product analysisStoichiometry of the reaction was ascertained by equilibrating the reaction mixture containing an excess of N-bromosaccharin (≈10 times) over the concentration of acetophenone and the concentration of acetic acid and mercuric acetate was maintained at experimental runs. Stoichiometric studies revealed that 1 mol of acetophenone consumed 2 mols of NBSA in the presence as well as absence of surfactant. The stoichiometric equation can be written as: