SUMMERY
[Dr. D. V. Jagtap (Chemistry)]
Minor Research Project Entitled
“Environmentally Friendly Reactions in Ionic Liquids”
Ionic liquids (ILs) are proving to be promising media as a solvent for green synthesis
and for the novel applications in chemistry. ILs provides new options based upon different
chemical and physical properties as a solvent.Ideal solvent requirements may include low
toxicity, low cost, high solute selectivity, inertness to materials, non-flammability, high
capacity for solute low carrier selectivity, and moderate interfacial tension. ILs can meet
some of these requirements now, but it is costly and somewhat toxic.
Synthesis of ionic liquids [BMIM][PF6], [BMIM][BF4]
Above both IL require, 1-butyl-3-methylimidazolium chloride for their synthesis.
Therefore first step have been carried out to synthesize the same.
1.Synthesis of 1-butyl-3-methylimidazolium [BMIM] Cl:
2.Synthesis of 1-butyl-3-methylimidazolium hexafluorophosphate, [BMIM][PF6]
3. Synthesis of 1-butyl-3-methylimidazolium tetrafluoroborate, [BMIM][BF4]
Microbial Reduction of prochiral ketonesTo the wet mycelium in 50 ml phosphate buffer, 0.2 M (pH7.0). The substrate
(appropriate amount) were added and shaken for different time intervals(2-8 days) to get
maximum optical and chemical yields.
1) General Procedure for preparation of racemic alcohols (1a-2a):_
To a solution of the corresponding ketone 1a and 2a (200mg) in dry methanol 5 ml
was slowly added sodium borohydride at 00C. The reaction was stirred at room temperature
for 3 hour and follow by TLC analysis, until complete disappearance of the starting ketone.
Solvent was evaporate under reduced pressure and the resulting suspension was re-dissolved
in water and and extracted with ethyl acetate. Organic phase were combined and dried over
anhydrous MgSO4. After solvent distillation under reduced pressure, the resulting crude
product was purified by preparative TLC.
2) Procedure for the bio reduction of acetophenone derivative using
Rhizopusarrhizus, Geotrichumcandidum.
The growing cells of Rhizopusarrhizus, Geotrichumcandidumwere used for bio reduction
reaction. 1mmole of substrate were added into Erlenmeyer flask and the reactions were
shaken for 4 days, after adding 5 ml ethanol with or without 2 ml ionic liquid. The content of
each flask was saturated with sodium chloride and then aqueous phase was extracted with
ethyl acetoacetate (3×20 ml). The organic phase was dried over MgSO4and then the solvent
was evaporated under reduced pressure.
Results:[BMIM][BF4] and [BMIM] [PF6] ionic liquids were prepared by employing the
literature procedures.
+
N
N
CH3
Cl
Bu-Cl
+
N
N
CH3
N
NaBF4 Or
Cl
HPF6
N
BF4-/ PF6_
CH3
3-butyl-1-methylimidazolium tetrafluoroborate or hexafluorophosphate.
Alkylation of N-methylimidazole with an butyl chloride yielded 3-butyl-1butylimidazolium chloride as a white solid. Metathesis with sodium tetrafluoroborate yielded
the tetrafluoroborate salts as viscous oil. Crude ionic liquid contains chloride ion impurity,
which can be removed by carrying out metathesis in acetone from which the tetrafluoroborate
salts separate out as viscous oils.
3-butyl-1-methylimidazolium hexafluorophosphate was prepared from the halide by
metathesis with hexafluorophosphoric acid and purified by filtering through silica gel and
washing with saturated Na2CO3.
Bio reduction of acetophenone derivatives using Rhizopusarrhizus,Geotrichumcandidum,
O
H
HO
Rhizopus arrhizus
CH3
CH3
R
R
Geotrichum candidum IL/EtOH
1a-2a
1b-2b
Ketones:1a- NO2
1b- NO2
2a-Cl
2b-Cl
Chiral (S) alcohols
1) (S)-1-(4-nitrophenyl) ethanol. (1b) [𝛼]25
𝐷 =-24.6, C=0.5, CHCl3.
2) (S)-1-(4-chlorophenyl) ethanol. (2b) [𝛼]25
𝐷 =-32.1,CH2Cl2, C=0.5, for 62% ee of S
enantiomer.
3) pH Influence: Reactions were analyzed after 4 days at different pH’s 6.8,7.0,7.2. the
optimal pH for this bio catalytic system was 7.0.
ConclusionMicrobial reduction of prochiral ketones to chiral alcohols are green reactions .It has
been concluded that [BMIM][PF6] is hydrophobic ionic liquid than [BMIM][BF4] and
[BMIM][PF6] ionic liquid gives better results of reduction than [BMIM][BF4 ]