Selective Oxidation of Lauryl Alcohol to Lauraldehyde under Liquid-Liquid Phase Transfer Catalysis (LL-PTC) with Potassium Chromate as the Oxidizing Agent

摘要

In the present research, the selective oxidation of lauryl alcohol to lauraldehyde was studied under liquid-liquid phase transfer conditions using potassium chromate (K_2CrO_4) as an oxidizing agent and tetrabutyl ammonium bromide (TBAB) as the phase transfer catalyst. Chromium (Ⅵ) reagents are used in these oxidations since the alcohols are selectively oxidized to the aldehydes without any over-oxidation. In non-aqueous solutions the oxidation by chromium (Ⅵ) does not go to completion as the intermediate partially oxidized material containing chromium must be hydrolysed for oxidation to continue. Liquid-Liquid Phase Transfer Catalysis (LL-PTC) involves the transfer of one reactant from the aqueous phase to the organic phase with the help of small quantities of a phase transfer catalyst which is usually quaternary ammonium or phosphonium salt. It was observed that no over-oxidation products such as lauric acid and high molecular weight esters of lauryl alcohol were formed under the reaction conditions used. The effect of various reaction parameters such as the speed of agitation, temperature, the concentration of lauryl alcohol, the concentration of potassium chromateand phase transfer catalyst loading were studied. A reaction mechanism involving the formation of chromate ester in the organic phase has been proposed and a kinetic model has been developed based on the experimental results obtained.