S. Backlund et al., ENZYMATIC ESTERIFICATION AND PHASE-BEHAVIOR IN IONIC MICROEMULSIONS WITH DIFFERENT ALCOHOLS, Colloid and polymer science, 273(6), 1995, pp. 533-538
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.