Reasearch On Etherification And Esterification Reaction By DBSA And Microemulsions Catalytic

Organic ethers and esters are important classes of chemicals which have considerable applications in different areas of chemical industry such as herbicides, disinfectors, pharmaceuticals, plasticizers, solvents and intermediates. Gemerally, direct esterification and etherification is carried out in organic solvents and needs either of two methods to shift the equilibrium between reactants and products.One is removal of water generated as the reactant proceed and the other is use of large excess amounts of one of the reactants. Now ,we usually use concentrated sulfuric acid as catalyst .As catalyst,it is inexpensive and active, but it induses series of by products, because of its oxidative and dehydative.And concentrated sulfuric acid is corrosive ,making lot of waste acid as well as the reaction of sulfur dioxide emissions will cause serious environmental pollution. So replacing the catalyst has received considerable attention in both esterification and etherification.Microemulsion is clear, thermodynamically stable fluids of water, oil, and surfactants and is considered as less toxic, less expensive relative to many other solvents. It is excellent medium for organic reactions because of its very large interfacial area and its ability of overcoming incompatibility of the reagents. The large oil–water interface of microemulsions can be used as templates for organic reactions.Organic molecules with one more polar and one less polar end will accumulate at the oil–water interface of microemulsions. They will orient at the interface so that the polar part of the molecule extends into the water domain and the nonpolar part extends into the hydrocarbon domain. This tendency for orientation at the interface can be taken advantage of to induce regiospecificity of an organic reaction. Therefore ,in recent years ,as a reaction medium for chemical preparation and organic reactions microemulsion has become one of colloid and interface research focuses currently.Dodecylbenzenesulfonic acid (DBSA) are both Br?nsted acid and surfactant, so it can act as an acid catalyst to activate a substrate and as a surfactant to form stable microemulsion with water-insoluble substrates. We called this kind of catalyst as the Br?nsted acid-surfactant-combined catalyst (BASC). In the previous work, we have studied the esterification in the DBSA microemulsion system in which DBSA acts as surfactant and acid catalyst. The results showed that the remarkable high esterification conversion was obtained in the relatively mild conditions. In the present work, we have studied the Crotonic acid hexyl ester and 1-hexyl benzoate in the DBSA microemulsion system in which DBSA acts as surfactant and acid catalyst. The results showed that the remarkable high esterification conversion also was obtained in the relatively mild conditions.we investigated direct etherification of two different alcohols in the DBSA microemulsion system and studied complicated esterification in the DBSA microemulsion system. The etherification reaction between hexanol and tert-butyl alcohol was selected as the model reaction and the effect of reaction parameters such as w0 ([H2O]/ [surfactant]), molar ratio of reactants, system temperature and the concentration of surfactant on conversion was studied. Furthermore, it was found that the best reaction conditions could be applied to many other etherification reactions and the product conversion was also high. it is believed that DBSA microemulsion should also be applicable to synthesis of aryl ether, thioether, heterocyclic ether and naphthyl ether and the relative works.