Synthesis of novel greener functionalized ionic liquids containing appended hydroxyl

Article abstract of DOI:10.1080/00397910701465230

Novel "greener" functionalized ionic liquids have been prepared by the reaction of 1,2-epoxy propane and dilute sulfuric acid with [EMIm]Br or [BMIm]Br formed by alkyl bromide (RBr) and 1-methylimidazole. This kind of ionic liquid could be possibly used as green solvent and catalyst, especially as phase-transfer catalyst in organic chemistry (e.g., the synthesis of ethoxybenzene). Their chemical structures were characterized by 1H NMR, 13C NMR, and IR. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910701465230

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Synthesis of Novel Greener Functionalized
Ionic Liquids Containing Appended Hydroxyl
a
a
a
a
Guo Ren Feng , Jia Jian Peng , Hua Yu Qiu , Jian Xiong Jiang , Lan Tao
a
a
&
Guo Qiao Lai
a
Key Laboratory of Organosilicon Chemistry and Material Technology of
Ministry of Education , Hangzhou Teachers College , Hangzhou, China
Published online: 14 Aug 2007.
To cite this article: Guo Ren Feng , Jia Jian Peng , Hua Yu Qiu , Jian Xiong Jiang , Lan Tao & Guo Qiao Lai
(
2007) Synthesis of Novel Greener Functionalized Ionic Liquids Containing Appended Hydroxyl, Synthetic
Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry, 37:16,
671-2675, DOI: 10.1080/00397910701465230
2
To link to this article: http://dx.doi.org/10.1080/00397910701465230
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Synthetic Communications , 37: 2671–2675, 2007
Copyright # Taylor & Francis Group, LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910701465230
Synthesis of Novel Greener Functionalized
Ionic Liquids Containing Appended
Hydroxyl
Guo Ren Feng, Jia Jian Peng, Hua Yu Qiu, Jian Xiong Jiang,
Lan Tao, and Guo Qiao Lai
Key Laboratory of Organosilicon Chemistry and Material Technology of
Ministry of Education, Hangzhou Teachers College, Hangzhou, China
Abstract: Novel “greener” functionalized ionic liquids have been prepared by the
reaction of 1,2-epoxy propane and dilute sulfuric acid with [EMIm]Br or [BMIm]Br
formed by alkyl bromide (RBr) and 1-methylimidazole. This kind of ionic liquid
could be possibly used as green solvent and catalyst, especially as phase-transfer
catalyst in organic chemistry (e.g., the synthesis of ethoxybenzene). Their chemical
1
13
structures were characterized by H NMR, C NMR, and IR.
Keywords: ethoxybenzene, functionalized, 2-hydroxypropyl sulfate, ionic liquid
1
. INTRODUCTION
Ionic liquids are molten salts at ambient temperatures that typically composed
of organic nitrogen-containing heterocylic cations and organic or inorganic
[
1,2]
anions.
Ionic liquids have been attracting significant and growing
interest because of their intrinsic useful properties, such as low melting
point, negligible volatility, high ionic conductivity, good thermal stability,
and wide electrochemical window.
Received December 27, 2006
Address correspondence to Lan Tao, Key Laboratory of Organosilicon Chemistry
and Material Technology of Ministry of Education, Hangzhou Teachers College,
Hangzhou 310012, China. E-mail: taulan@163.com
2
671

2
672
G. R. Feng et al.
During past decades, ionic liquids were recognized as a novel class of
environmentally friendly solvents for both organic and inorganic materials,
replacing traditional volatile organic solvents in catalysis and organic trans-
[
formations. However, typically the ionic liquid systems used in the literature
3]
2
consist of halogen-containing anions such as [AlCl ] , [Al Cl ] , [BF ] ,
2
2
4
2
2
7
4
2
2
2
2
2
[
[
PF ] , [SbF ] , [C F SO ] , [CF CO ] , [C F CO ] , [CF SO ] ,
6 6 4 9 3 3 2 3 7 2 3 3
2
(CF SO ) N] , [SnCl ] , and [Sn Cl ] , which are usually combined with
2
2
3
3 2
3
4]
2
5
[
imidazolium cations. For some reasons, these ionic liquids are often
regarded as green solvents. With regard to the environmental impact of
technical processes using these ionic liquids, under certain conditions, their
2
2
presence may cause serious concerns. The anions [AlCl4] and [PF6]
hydrolyze easily if water is present, significant amounts of HCl and HF
would be liberated under some reaction conditions. Furthermore, that may
be the case for the potential disposal of technical amounts of spent ionic
liquid by thermal treatment. Considering those cases, we have to make an
effort to avoid the liberation of toxic and corrosive HCl and HF into our
[5]
environment using ionic liquids. Then we decided to design new, even
greener ionic liquids through modifying the anion for catalytic application.
In this article, we present in detail the synthesis and characterization of
new imidazolium-based ionic liquids (I and II) containing a 2-hydroxypropyl
2
3
sulfate anion (CH CH(OH)CH OSO ). The ionic liquids were synthesized by
3
2
the route shown in Scheme 1.
These ionic liquids contain a functionalized anion and could not only
influence the physical properties but also the chemical properties, especially
the solubility and catalytic capability. This kind of ionic liquid has excellent
properties common to green ionic liquids and has the relatively hydrolysis
2
labile anion CH CH(OH)CH OSO , which would generate the sulfate ion
3
2
3
and 1,2-propanediol. They may be employed as phase-transfer catalyst and
have a similar effect with Br a¨ ndstr o¨ m catalyst (TBAB). They also could
form acidic conditions for certain reactions. We use these ionic liquids as
efficient catalysts for the synthesis of ethoxybenzene, Mannich reaction, and
Pinacol rearrangement reaction. We have investigated the reaction of
Scheme 1.

Synthesis of Novel Greener Functionalized Ionic Liquids
2673
Scheme 2.
ethoxybenzenes synthesis employing ionic liquids II to promote the trans-
formation (see Scheme 2).
2
2
.
EXPERIMENTAL
.1. Preparation of [EMIm]Br and [BMIm]Br
To a 250-mL flask equipped with a magnetic stirrer and a reflux condenser,
RBr (0.12 mol), 1-methylimidazole (0.10 mol), and 1,1,1-trichloroethane
(20 mL) were added. The mixture was heated in an oil bath, refluxing for
6 h. After being cooled to room temperature, the organic layer was removed
from the flask by decanting. The obtained solid product was washed with
ethyl acetate (2 Â 15 mL) and then evaporated in vacuo at 708C.
[6]
2
.2. Preparation of Ionic Liquids (I and II)
[
(
(
EMIm]Br or [BMIm]Br obtained as discussed and 1,2-epoxy propane
0.78 mol) were vigorously stirred in an ice bath. The dilute sulfuric acid
consisting of 4.3 mL of concentrated sulfuric acid and 31.2 mL of water)
was added dropwise to the flask over about 45 min. Meanwhile, the tempera-
ture was kept colder than 108C during this process. The ice bath was then
removed, and the reaction carried out at room temperature for a further
2
4 h. The reaction mixture was extracted with ethyl ether (3 Â 30 mL) and
the aqueous phase was evaporated under reduced pressure to afford transpa-
rent liquids I and II, respectively. The ionic liquid was dried in a vacuum
drying oven at 808C for 10 h and obtained finally in the form of a viscous
clear liquid, which corresponded to about 95% of the theoretical yield.
2
.3. Synthesis of Ethoxybenzene Promoted by Ionic Liquids
Phenol (0.05 mol) was dissolved in a vigorously stirred aqueous NaOH
solution (6.0 N, 10 mL). Ethyl bromide (0.10 mol) and ionic liquid (II)
(0.005 mol) were added carefully to the solution. The resulting biphasic
mixture was refluxed for 5 h. After being cooled to room temperature, the
organic phase was separated. The dissolved organic species in aqueous
phase was extracted by ethyl ether (3 Â 20 mL) and combined with the

2
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G. R. Feng et al.
organic phase. The combined organic phase was washed with aqueous NaOH
solution (10%, 15 mL), then water (2 Â 15 mL), and dried over Na SO . Ethyl
2
4
ether was rotary evaporated, and the colorless liquid was obtained with yield
of 93.0%.
3.
CHARACTERIZATION
3.1. Characterization of Ionic Liquid I
1
H NMR (400 MHz, D O, d ppm relative to TMS): 8.63 (s, 1H), 7.40 (s, 1H),
2
7
.33 (s, 1H), 4.15 (q, 2H), 3.80 (s, 3H), 1.41 (t, 3H), 1.12 (q, 2H).
3
1
C NMR (400 MHz, CDCl , d ppm relative to TMS): 135.48 (Cimi),
3
123.33 (Cimi), 121.75 (Cimi), 72.79 (O-CH ), 65.49 [CH-(OH)], 44.65
2
(
N-CH ), 35.47 (N-CH ), 17.90 [CH -(CHOH)], 17.72 [(CH )-CH ].
2 3 3 2 3
2
1
IR (KBr Pellet, cm ): 3416 (yO-H), 3154, 3110, 2978 (yC-H), 1643
yC 55 C), 1573 (yC 55 N), 1454, 1385, 1336 (dC-H), 1220 [vs. CH CH(OH)CH
(
OSO ], 1171, 851, 765 (imidazolium ring), 1106 (yC-O).
3
2
2
3
3.2. Characterization of Ionic Liquid II
1
H NMR (400 MHz, D O, d ppm relative to TMS): 8.63 (s, 1H), 7.39 (s, 1H),
2
7
.34 (s, 1H), 4.11 (t, 2H), 3.80 (s, 3H), 1.76 (m, 2H), 1.24 (m, 3H), 1.16
q, 2H), 0.85 (t, 3H).
(
1
3
C NMR (400 MHz, CDCl , d ppm relative to TMS): 135.77 (Cimi),
3
123.38 (Cimi), 122.11 (Cimi), 72.77 (O-CH ), 65.50 [CH-(OH)], 49.15 (N-
CH ), 35.52 (N-CH ), 31.19 [(CH )-CH -(CH )], 17.93 [CH -(CH )], 12.56
2
2
3
2
2
2
2
3
[
(CH )-CH ].
2
3
2
IR (KBr pellet, cm ): 3416 (yO-H), 3151, 3108, 2964, 2936, 2875
1
(yC-H), 1644 (yC 55 C), 1573 (yC 55 N), 1465, 1381, 1337 (dC-H), 1221 [vs.
CH CH(OH)CH OSO ], 1171, 860, 765 (imidazolium ring), 1105 (yC-O).
2
3
3
2
3.3. Characterization of Ethoxybenzene
The combined organic phase was analyzed by GC/MS (Trace DSQ 2000),
revealing 95.7% of conversion from phenol to ethoxybenzene.
ACKNOWLEDGMENTS
We are grateful to Hangzhou Teachers College Science Foundation (2006
XNZ08) for financial support.

Synthesis of Novel Greener Functionalized Ionic Liquids
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