ENZYMATIC ESTERIFICATION AND PHASE-BEHAVIOR IN IONIC MICROEMULSIONS WITH DIFFERENT ALCOHOLS

The esterification of hexanoic acid and 1-pentanol catalyzed by the li pase from Chromobacterium viscosum was studied at 298.2 K using differ ent Winsor systems as reaction medium. The microemulsion systems consi sted of brine and alkane stabilized by the anionic surfactant sodium d odecylsulphate and a short-chained alcohol. The alcohol acts both as a reactant and as a part of the reaction medium. Therefore, it is of gr eat fundamental interest to know the phase behavior of the used microe mulsion systems. Partial phase diagrams were determined and the effici ency of different alcohols on the transition from a Winsor I system to a Winsor III or a Winsor IV system with bicontinuous structure and fu rther to a Winsor II system was investigated The investigated alcohols were 2-methyl-1-propanol, 1-butanol, 2-butanol, 2-methyl-1-butanol, 3 -methyl-1-butanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-pent anol, 3-methyl-1-pentanol, 4-methyl-1-pentanol and 1-hexanol. The aque ous medium consisted of 0.5 m NaCl(aq) or a phosphate buffer (pH = 7) and the organic medium of octane or 2,2,4-trimethyl pentane. A long al kyl chain of the alcohol or a branching far from the hydroxyl group gi ves a more efficient cosurfactant and a transition from Winsor I to Wi nsor III or Winsor IV at lower alcohol contents. In the Winsor III sys tem the yield of l-pentyl hexanoate is twice as high as the yield in t he bicontinuous Winsor IV system.