Southern Illinois University Edwardsville, Chemistry, Edwardsville, IL 62026
Phase transfer catalysis is proposed as a method for allowing nucleophilic displacement reactions to occur where the nucleophile and the organic substance are not soluble in the same solvent. This is a technique is used to conduct a reaction between reagents in two or more separate phases that do not come together to react under normal conditions. We performed nucleophilic displacement reaction either as a biphase reaction, or a triphase reaction using a solid support to immobilize the catalyst as the third phase. A modified hectorite clay was used as the solid support. Triphase catalysis is a form of heterogeneous catalysis, in which the catalyst, organic phase, and aqueous phase are all located in separate phases. The major advantage of triphase catalysis over biphase catalysis is that catalyst can be recovered from the product mixture by simple filtration and also can be recycled for further application. In this research, the conversion of n-hexylbromide to n- hexylacetate has been investigated using the modified clay. The catalysts tetraoctadecylammonium bromide, tetrahexadecylammonium bromide and tetradodecylammonium bromide were intercalated into interlayer regions of clay. The rate of the reactions in triphase system at various temperatures were obtained and compared to the corresponding rates of the biphase catalytic system. The activation energies were also obtained.
[Abstract (DOC)]