Role of surfactants on metal mediated cerium(IV) oxidation of valeraldehyde at room temperature and pressure

The short chain straight fatty acid, valeric or pentanoic acid is chemically significant for its huge applications in variety of industrial target compounds including plasticizers, lubricants, biodegradable solvents, perfumery and pharmaceuticals. Synthesis of valeric acid has been achieved by the cerium(IV) oxidation of a straight C-5 chain valeraldehyde which is a precursor of organic compounds. Ce(IV) is selected as an alternative oxidizing agent in place of higher valent metals. The oxidation kinetics of valeraldehyde has been investigated under pseudo-first-order conditions in acidic medium at 30 degrees C. Several transition metal salts: Cr(III), Mn(II), Ir(III) and Ru(III) have been introduced to observe their effect on reaction rate(6). Three different representative non-functional surfactants: Cetyltrimethylammonium bromide (CTAB; cationic), Sodium dodecylsulphate (SDS; anionic) and 3-[(3-cholamidopropyl) dimethylammonio]-1-propanesulfonate (CHAPS; zwitterionic) catalyze the reaction significantly. Ir(III) and Ru(III) enhance the oxidation rate in the presence and absence of surfactant. Cr(III), Mn(II) and Cu(II) interestingly inhibit the reaction rate. CMC values of the surfactants have been determined by spectrofluorometry and conductometry. The oxidized product valeric acid has been characterized by NMR and FTIR spectroscopy. Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) experiments support the aggregation of surfactants Ru(III) in association with CTAB micellar catalyst that exhibited a dramatic similar to 330 fold rate enhancement compared to the uncatalyzed reaction path. (C) 2015 Elsevier B.V. All rights reserved.