Schafer et al. have studied the selective recovery of the solutes
from the ionic liquid [bmim]PF6 by pervaporation [41]. As ionic
liquids are non-volatile, vacuum can be used to remove volatile
products such as water or alcohol, driving equilibrium toward product
formation [67]. The purpose of their work was to show that
it is possible to quantitatively and more effectively recover the
solutes from the ionic liquids than by distillation. It can be done
under milder process conditions (in comparison to distillation) and
without the need to employ volatile organic solvents (like withextraction). Only four papers were found on the topic of pervaporation
aided esterification in ionic liquid, two of which cover the topic
of an enantioselective reaction; kinetic resolution of racemic 2-
chloro-propanoic acid [43,68]. The remaining two systems include
the synthesis of ethyl acetate [44] and isoamyl acetate [42]. The
simplicity and applicability of systems involving ionic liquids is in
the fact that the upper phase could be easily removed and replaced
by the fresh substrate solution because the enzyme had remained
in the ionic liquid. Authors have showed that integration of pervaporation
with the biocatalytic process can increase the reaction
yield (Table 4).
Significant information on esterifications that were carried out
in ionic liquid as a solvent and were coupled by pervaporation is
presented in Table 4. Two reports on the kinetic resolution of 1-
butyl-2-chloropropanoic acid ester were given by the same group
of authors. In their first report Belafi-Bako et al. have investigated
esterification of 2-chloro propanoic acid with 1-butanol catalyzed
by C. rugosa lipase in the presence of different ionic liquids. Ester
yield was doubled when pervaporation was used to keep the water
content constant at 0.5% (Table 4). Enantioselectivity was found to
be slightly lower than in n-pentane as a solvent [43]. In a more
detailed work [68] the same esterification was studied in ionic
liquids ([bmim]PF4, [bmim]PF6 and [omim]PF6) and organic solvents
(n-hexane, toluene and tetrahydrofuran). If chlorine was
replaced by bromine substituent on the substrate molecule (acid)
enzyme enantioselectivity was improved. Relative enantioselectivity
of recycled C. rugosa lipase in [bmim]PF6 and [onim]PF6
decreased only 10 and 15%, while more than 50% decrease was
Schafer et al. have studied the selective recovery of the solutesfrom the ionic liquid [bmim]PF6 by pervaporation [41]. As ionicliquids are non-volatile, vacuum can be used to remove volatileproducts such as water or alcohol, driving equilibrium toward productformation [67]. The purpose of their work was to show thatit is possible to quantitatively and more effectively recover thesolutes from the ionic liquids than by distillation. It can be doneunder milder process conditions (in comparison to distillation) andwithout the need to employ volatile organic solvents (like withextraction). Only four papers were found on the topic of pervaporationaided esterification in ionic liquid, two of which cover the topicof an enantioselective reaction; kinetic resolution of racemic 2-chloro-propanoic acid [43,68]. The remaining two systems includethe synthesis of ethyl acetate [44] and isoamyl acetate [42]. Thesimplicity and applicability of systems involving ionic liquids is inthe fact that the upper phase could be easily removed and replacedby the fresh substrate solution because the enzyme had remainedin the ionic liquid. Authors have showed that integration of pervaporationwith the biocatalytic process can increase the reactionyield (Table 4).Significant information on esterifications that were carried outin ionic liquid as a solvent and were coupled by pervaporation ispresented in Table 4. Two reports on the kinetic resolution of 1-butyl-2-chloropropanoic acid ester were given by the same groupof authors. In their first report Belafi-Bako et al. have investigatedesterification of 2-chloro propanoic acid with 1-butanol catalyzedby C. rugosa lipase in the presence of different ionic liquids. Esteryield was doubled when pervaporation was used to keep the watercontent constant at 0.5% (Table 4). Enantioselectivity was found tobe slightly lower than in n-pentane as a solvent [43]. In a moredetailed work [68] the same esterification was studied in ionicliquids ([bmim]PF4, [bmim]PF6 and [omim]PF6) and organic solvents(n-hexane, toluene and tetrahydrofuran). If chlorine wasreplaced by bromine substituent on the substrate molecule (acid)enzyme enantioselectivity was improved. Relative enantioselectivityof recycled C. rugosa lipase in [bmim]PF6 and [onim]PF6decreased only 10 and 15%, while more than 50% decrease was
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