Note: Descriptions are shown in the official language in which they were submitted.
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TITLE: PREPARATION OF IONIC LIQUIDS
FIELD OF THE INVENTION:
The present invention relates to the field of
organic chemistry. In particular, the invention relates to
the preparation of ionic liquids.
BACKGROUND OF THE INVENTION:
Low melting organic salts, also known as "ionic
liquids", have found utility as solvents for example in
organic synthesis, electrochemistry, and catalysis. They may
also be used as phase-transfer catalysts, liquid-membrane
materials, thermal transfer fluids, high temperature
lubricants, plasticizers, in separation sciences, and as a
component in electrical storage devices (such as
electrochemical capacitors, batteries and fuel cells).
Ionic liquids provide an attractive potential
alternative to traditional organic solvents for chemical
reactions for many reasons. For industrial purposes, the low
vapour pressure of ionic liquids is a very important feature.
They are essentially non-volatile, a property that eliminates
many of the containment problems typically encountered with
traditional organic solvents. Since ionic liquids are often
composed of poorly coordinating ions, they have the potential
to provide a highly polar yet poorly coordinating solvent.
Moreover, many of these solvents are immiscible with
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traditional organic solvents and therefore provide a non-
aqueous polar alternative to two-phase systems. Because of
their distinctive solvent characteristics, they can be used
to bring unusual combinations of reagents into the same
phase. A recent review of the properties and uses of ionic
liquids is provided in an article entitled "Room-Temperature
Ionic Liquids. Solvents for Synthesis and Catalysis," by
Thomas Welton (Chem. Rev. 1999, 99, 2071-2083).
Non-halide based ionic liquids (i.e. ionic liquids
having an anion other than a halide) can be prepared by
metathesis of an organic halide salt with an alkaline metal
non-halide salt or acid (see: Wilkes et al. (1992) J. Chem.
Soc. Chem. Comm. 965; U.S. Patent No. 5,683,832; Bonhote et
al. Snorg. Chem (1996) Vol. 35 (5), 1168-1178; U.S. Patent
No. 5,827,602; U.S. Patent No. 5,182,405; WO 0016902; WO
0140146; WO 0187900; WO 0279212; and WO 0294883). However,
conventional metathesis reactions have several drawbacks.
For example, when carried out on a commercial scale, these
reactions generate large quantities of organic and solid
wastes. Also, conventional metathesis produces yields that
are considerably less than 100%, more typically in the range
80-90%. These low yields are due at least in part to the
fact that anion exchange readily establishes an equilibrium
among the ions. Acid/base neutralization reactions can be
used to prepare ionic liquids but this would require
preparation of the phosphonium, imidazolium or ammonium
hydroxides first. These are generally prepared from the
corresponding halide.
Non-halide based ionic liquids prepared by
conventional metathesis typically contain various
contaminants, such as halide ions. For many purposes, the
presence of halide ions is undesirable. For example, the
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presence of halide ions may interfere with transition metal
catalysts, such as palladium catalysts.
Halide ions and other contaminants are typically
removed from ionic liquids produced by metathesis by washing
with water, filtering and drying the ionic liquid. The
additional purification steps reduce the overall economy of
the process, generating aqueous waste that must be disposed
of and reducing overall yield of ionic liquid product.
Further, available processes for preparing ionic
liquids often use an excess of reagents such as alkaline
metal salts, large quantities of water and organic solvents
such as methylene chloride, acetone and acetonitrile.
There remains a need for more economical and
efficient methods for preparing non-halide based ionic
liquids on a commercial scale. There further remains a need
for methods of preparing non-halide based ionic liquids that
reduce the amount of halide ion present in the final product.
SUMMARY OF THE INVENTION:
The current invention provides a method for
preparation of a compound of formula (I) QA-, the method
comprising reacting:
(i) an organic halide salt of formula (II)
Q+X-, wherein
Q+ is an organic cation and
X-, is a halide;
with
(ii) a Bronsted acid other than a hydrohalic
acid, wherein said Bronsted acid has a conjugate base A-; and
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(iii) an alcohol or an alkene or an alkyne;
so as to produce Q+A- and hydrocarbyl halide, and when said
alcohol is used as a reagent, water;
with the proviso that when Q+ is 1-butyl-3-
methylimidiazolium, the Bronsted acid is not H2SO4 or CH3SO3H.
For some purposes, the presence of halide ion in
the product QA- is not of concern. However, for other
purposes, the presence of halide ion in the product Q+A- is
undesirable. The method may be used to obtain a product Q+A-
that is completely or substantially free of halide, i.e. if
it contains halide, the level of halide ion is sufficiently
low that the halide ion does not interfere with the intended
utility of the product Q+A-. For some halide-sensitive
applications, compounds of formula (I) that contain small
amounts of halide ions may be acceptable, for example in an
amount ranging up to about 1000 parts per million (ppm), but
preferably ranging up to only about 500 ppm, more preferably
300 ppm and even more preferably only up to 200 ppm.
Desirably the amount of halide present in the product Q{A'
does not produce detectable precipitate in,a AgNO 3 test.
DETAILED DESCRIPTION:
In accordance with the present invention, a
compound of formula (I) compound Q+A- is prepared by reacting
(i) an organic halide salt (Q+X-) with (ii) a Bronsted acid
other than a hydrohalic acid and having a conjugate base A-
and (iii) an alcohol or an alkene or an alkyne. This
reaction also produces a hydrocarbyl halide and, when alcohol
is used as a reagent, water.
Q+X- may be any organic halide salt, i.e. wherein X"
is fluoride, chloride, bromide, or iodine. Preferably, X- is
chloride or bromide.
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Suitable cations for Q+X- include those that have
at least one quaternary nitrogen atom or quaternary
phosphorus atom having at least one hydrocarbyl group
attached thereto, wherein the hydrocarbyl group is a Ci-C30
5 alkyl, C1-C30 alkyloxy, C3-C7 cycloalkyl, C3-C7 cycloalkyloxy,
C6-C18 aryl, C6-C18 aryloxy, C7-C30 aralkyl, or C7-C30
aralkyloxy. The hydrocarbyl group or groups present on the
organic cation are preferably C1-C14 alkyl groups, more
preferably C1-C6 alkyl groups. When more than one
hydrocarbyl group is present, the groups may be identical or
different. The hydrocarbyl groups may be straight-chained or
branched. Further, the hydrocarbyl groups may be substituted
or unsubstituted or contain heteroatoms, provided that the
substituents or heteroatoms do not interfere with the method
of preparing Q+A-. Acceptable heteroatoms may include
oxygen, silicon, and sulfur, and acceptable substituents
include alkoxy, alkylthio, acetyl, and halogen atoms, such as
fluorine. Suitable hydrocarbyl groups include: methyl,
ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, sec-butyl,
n-pentyl, iso-pentyl, 2-pentyl, n-hexyl, phenyl, octyl,
decyl, undecyl, and tetradecyl. The quaternary nitrogen atom
or quaternary phosphorus atom may be a ring-member in for
example a five- or six-membered ring system containing one to
five carbon atoms, unsubstituted or substituted for example
with a hydroxy group or a hydrocarbyl group as described
above, and optionally containing additional heteroatoms, such
as nitrogen, oxygen and sulfur.
Thus, examples of organic halide salts for use in
the current method include but are not limited to: ammonium
salts, phosphonium salts, pyridinium salts, imidazolium
salts, pyrazolium salts, pyrimidinium salts, pyridazinium
salts, pyrazinium salts, triazolium salts (both 1,2,3-
triazolium and 1,2,4-triazolium), tetrazolium salts, and
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isothiazolium salts. Mention is made of the following
organic halide salts: trihexyltetradecylphosphonium chloride;
tetrabutylphosphonium bromide; tetraoctylphosphonium bromide;
tetrapropylammonium bromide; tetrabutylammonium bromide; N-
butylpyridinium bromide; 1-propyl-3-methylimidazolium bromide
(pmim-Br); 1-butyl-3-ethylimidazolium bromide (beim-Br);
1-hexyl-3-ethylimidazolium bromide (heim-Br);
1-butyl-3-ethylimidazolium chloride (beim-Cl); and
N-hexyl-3-picolinium bromide.
Some organic halide salts are commercially
available. Alternatively, organic halide salts can be
prepared by the reaction of an appropriate halogenoalkane
with an appropriate nitrogen-containing or phosphorus-
containing organic compound, such as an amine or phosphine.
HA may be any Bronsted acid (i.e. an acid having a
proton and conjugate base) other than a hydrohalide. The
conjugate base A- of the Bronsted acid may be any anion other
than a halide anion, including but not limited to: RS03-,
camphorsulfonates, RS02-, RS04-, H2PO4-, H2P03-, (RO) 2P (0) O-,
(R) P(O) (OH) O-, (R) 2P (O) O-, RC02-, N03-, N02-, C104-, phenolates,
HCrO4-, H2AsO4-, HzAsO3-, HSeO3-, HTeO6-, and HTeO3-, wherein R
is a hydrogen atom or a hydrocarbyl group. When Q' has a
quaternary phosphorus atom or quaternary nitrogen atom, A-
can also be (RS02)2N-. Suitable R hydrocarbyl groups include:
Cl-C30 alkyl, C2-C30 alkynyl, C2-C30 alkenyl, C3-C7 cycloalkyl,
C3-C7 cycloalkenyl, C6-Cla aryl, C7-C30 aralkyl,
C$-C30 aralkenyl, or C$-C30 aralkynyl. R may be substituted or
unsubstituted or contain heteroatoms, provided that the
substituents or heteroatoms do not interfere with the method
of preparing Q+A-. Acceptable heteroatoms may include
oxygen, nitrogen, silicon, and sulfur, and acceptable
substituents include alkoxy, alkylthio, acetyl, and halogen
atoms, such as fluorine. Examples of specific anions
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include: (CF3SO2) 2N-; CF3 (CF2) 2CO2-; CF3 (CF2) 3SO3-; CH3SO3-; HS04-;
and H2P04 Mention is made of the following non-limiting
examples of Bronsted acids: methanesulfonic acid,
bis(trifluoromethanesulfonyl)imide, DL-camphorsulfonic acid,
sulfuric acid, benzoic acid, naphthoic acid, nitrobenzoic
acid especially para-nitrobenzoic acid, chlorobenzoic acid
especially ortho-chlorobenzoic acid, saturated fatty acids
(such as palmitic acid) and unsaturated fatty acids (such as
oleic acid).
If the Bronsted acid includes a group R that
contains a hydroxyl or alkenyl or alkynyl moiety, the
Bronsted acid itself may undergo halogenation, and it may
therefore be unnecessary to add a further alcohol, alkene or
alkyne reagent to react with halide. Of course, a further
alcohol, alkene or alkyne can be added, if desired.
Water-sensitive anions are less suitable for use in
reactions in the presence of an alcohol, where water is
generated. Water-sensitive anions include aluminum (III)
halides. Water-sensitive anions may be used for reactions
involving alkenes and alkynes.
The alcohol may be a primary, secondary, or
tertiary alcohol. Alcohols having between one and ten carbon
atoms are preferred, with alcohols having between one and
four carbon atoms being more preferred. Examples of alcohols
include: methanol, ethanol, n-propanol, iso-propanol, n-
butanol, sec-butanol, tert-butanol, pentanol, hexanol,
heptanol, octanol, nonanol and decanol.
The alkene may be a C2-C30 alkene, a C3-C7
cycloalkene, a (C3-C7 cycloalkenyl) C1-C30 alkane, a (C3-C7
cycloalkane) C2-C30 alkene, or a(Cg-C10aryl) C2-C30 alkene. C2-
C12 alkenes are preferred, and C2-C6 alkenes are more
preferred. The alkene may be straight-chained or branched.
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Examples of alkenes include: propene, butene, hexene,
cyclopentene, and cyclohexene.
The alkyne may be a C2-C30 alkyne, a (C3-C7
cycloalkyl) C2-C30 alkyne, a(C3-C7 cycloalkenyl) Cz-C30 alkyne
or a(C6-C10 aryl) C2-C30 alkyne. C2-C12 alkynes are preferred,
and C2-C6 alkynes are more preferred. The alkyne may be
straight-chained or branched. Examples of alkynes include:
acetylene, propyne, butyne, pentyne, hexyne.
Examples of compounds of formula (I) QA- include
those represented by the following formulae:
/R i ~O-R R'
N N i
CG X O X , ~ X
~
\R \R R
CH3 CH3 CH3
N
G X ' G X + X
N\ N\ N\
R O R
R
(R)4N+X- and (R) 4P+X-,
wherein R and R' are alkyl radicals with 1 to 12 carbon
atoms, and
X- is (CF3SO2) 2N-, CF3 (CF2) zCOz-, CF3 (CF2) 3SO3-,
CH3SO3 , HS04 , or H2P04 .
Mention is made of the following compounds of
formula (I) :
trihexyltetradecylphosphonium methanesulfonate;
tetrabutylphosphonium methanesulfonate;
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tetraoctylphosphonium methanesulfonate;
tetrabutylphosphonium D-(+)-camphorsulfonate;
tetrapropylammonium methanesulfonate;
tetrabutylammonium methanesulfonate;
N-butylpyridinium methanesulfonate;
1-propyl-3-methylimidazolium methanesulfonate;
1-butyl-3-ethylimidazolium methanesulfonate;
1-hexyl-3-ethylimidazolium methanesulfonate;
1-butyl-3-ethyli.midazolium methanesulfonate
1-butyl-3-ethylimidazolium DL-camphorsulfonate;
1-butyl-3-methylimidazolium
bis(trifluoromethanesulfonyl)imide;
N-hexyl-3-picolinium
bis(trifluoromethanesulfonyl)imide;
tetrabutylphosphonium
bis(trifluoromethanesulfonyl)imide; and
tetraoctylphosphonium
bis(trifluoromethanesulfonyl)imide.
In general, the organic halide salt and alcohol or
alkene or alkyne can be reacted in stoichiometric amounts,
although the alcohol or alkene or alkyne may be present in
excess, for example about 1.1 to about 12 equivalents
relative to the organic halide salt. In particular, it will
be preferred in some cases to use an excess alcohol or alkene
or alkyne (for example between about 1.1 to about 12
equivalents, preferably about 2 to about 12 equivalents,
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relative to the organic halide salt) to promote the
conversion of halide ion to hydrocarbyl halide, so as to
reduce the amount of halide ion that is present in the non-
halide based ionic liquid product.
5 In general, the organic halide salt and the
Bronsted acid can be reacted in stoichiometric amounts,
although the Bronsted acid may be present in excess, for
example about 1.01 to about 12 equivalents, preferably about
1.01 to about 1.3 equivalents, relative to the organic halide
10 salt.
The reaction may be carried out by reacting organic
halide salt with Bronsted acid and alcohol or alkene or
aralkyne simultaneously. Alternatively, the reaction may be
carried out in sequential steps: reacting organic halide salt
Q+X- and Bronsted acid to obtain Q+A- and H+X-, then adding
alcohol or alkene or aralkyne to convert H+X- to hydrocarbyl
halide, and when alcohol is used, to hydrocarbyl halide and
water.
The organic halide salt can be generated in situ,
for example by reacting a hydrocarbyl halide with a reactant
containing group Q, for example a tertiary nitrogen-based or
tertiary phophorous-based compound (such as a tertiary amine,
tertiary phosphine, imidazole, etc.), optionally in the
presence of an alcohol, prior to the addition of the Bronsted
acid.
In general, the reaction can be carried out over a
wide range of temperatures, for example from between about
0 C to about 150 C, and pressures. The reaction is
conveniently carried out at elevated temperatures, for
example in the range of between about 100 C to about 150 C,
and atmospheric pressure. Reaction times may range from
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minutes to days, depending on conditions and particular
reagents, but typically are on the order of 1 to 72 hours,
more typically from about 2 to 24 hours.
Particularly in reactions where the Bronsted acid
is a weak acid (such as a carboxylic acid, phosphonic acid or
phosphinic acid), to facilitate formation of hydrocarbyl
halide, it may be beneficial to add a small amount of a
strong acid such as sulfuric acid. The strong acid is added
in a small amount, for example in an amount ranging from
about 0.001 equivalents to about 0.1 equivalents, preferably
from about 0.001 equivalents to about 0.05 equivalents, more
preferably from about 0.001 equivalents to about 0.01
equivalents, relative to the organic halide salt.
When the Bronsted acid is a carboxylic acid and an
alcohol is present, formation of esters may compete with
formation of hydrocarbyl halide. Formation of esters can be
inhibited by adding water to the reaction mixture to shift
the equilibrium of the esterification reaction to discourage
formation of the esters. For example, water may be added in
an amount ranging from about 0.01 equivalents to about 2
equivalents, preferably about 0.1 equivalents to about 1
equivalents, relative to organic halide salt.
The product Q+A- can be isolated by removing
unreacted starting materials, hydrocarbyl halide and water,
if present. Hydrocarbyl halide, unreacted starting materials,
and water, if present, can be removed from the reaction
mixture, for example by distillation, evaporation,
extraction, or decantation. Distillation and evaporation are
convenient methods for removing hydrocarbyl halides,
unreacted starting materials, and water from the reaction
mixture. Fractional distillation can be used to recover
hydrocarbyl halide and unreacted alcohol or alkene.
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Hydrocarbyl halide may also be removed by extraction, for
example with hexane. Water and unreacted acid may be removed
by distillation or evaporation, for example, under reduced
pressure. In some cases, water may be removed by
decantation.
The halide content of the product Q+A- can be
assessed with AgNO3 test or by electrochemical methods. If
the halide content of the Q+A- is unacceptably high, it may
be treated to reduce the amount of residual halide ion. The
amount of halide ion in the product Q+A- can be reduced by
adding to the product Q+A- a further quantity of alcohol or
alkene or alkyne (under conditions similar to those described
above) to convert residual halide ion to hydrocarbyl halide.
The product Q+A- may then isolated by removing hydrocarbyl
halide and water, if present, and unreacted starting
materials by for example distillation. This procedure can be
repeated as necessary to reduce the halide content of product
Q+A .
The product Q+A- obtained by the foregoing methods
can be used directly or further purified, for example by
dissolving it in a solvent (such as an alcohol, for example
methanol, ethanol, propanol and isopropanol), mixing with
activated carbon or charcoal, filtering, and removing solvent
by for example evaporation under reduced pressure.
Hydrocarbyl halide removed from the reaction
mixture can be recovered for use in chemical reactions. For
example, recovered hydrocarbyl halide can be used for
quaternization of imidazoles, pyridines, trialkylamines and
trialkylphosphines to generate halide-based organic salts.
If the halide-based organic salt is for use in generating a
compound of formula (I) Q+A- according to the methods
described herein, then it will be preferred that the solvent,
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if present, for carrying out the quaternization reaction is
an alcohol having a carbon backbone corresponding to that of
the hydrocarbyl halide reagent.
Alcohol recovered from the reaction mixture can be
recycled for use for example in subsequent chemical
reactions, including but not limited to the current method
for preparation of non-halide based ionic liquids.
The current invention is further illustrated by way
of the following non-limiting examples.
Example 1: Preparation of trihexyltetradecylphosphonium
methanesulfonate:
To a 125 ml two-neck round-bottom flask mounted
with a 30 cm fractional distillation column were added
trihexyltetradecylphosphonium chloride (51.8 g, 0.1 mol) and
methanesulfonic acid (redistilled, 9.61 g, 0.1 mol). Ethanol
(2 equivalent, redistilled) was added into the mixture. The
mixture was heated to 100 C using an oil bath, and
chloroethane was removed from the reaction mixture by
distillation under ambient pressure. Water and ethanol were
removed by evaporation under reduced pressure.
A further 2 eq. of ethanol was added to the
reaction vessel. The reaction vessel was heated to 1000.
Chloroethane was again removed via distillation. Water and
ethanol were again removed via evaporation under reduced
pressure. The foregoing process was repeated once more using
another equivalent of ethanol.
Trihexyltetradecylphosphonium methanesulfonate
ionic liquid product (colorless) was obtained in
approximately 100% yield at approximately 100% purity, as
confirmed by Nuclear Magnetic Resonance (NMR). No
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precipitate was observed when the ionic liquid was tested for
the presence of chloride using 10% aqueous AgN03.
Example 2: Preparation of tetrabutylphosphonium
methanesulfonate:
Tetrabutylphosphonium methanesulfonate was prepared
using the method described in Example 1, except that
tetrabutylphosphonium bromide (33.9 g, 0.1 mol),
methanesulfonic acid (redistilled, 9.61 g, 0.1 mol) and
ethanol (5 equivalent, redistilled) were used.
Tetrabutylphosphonium methanesulfonate was obtained
in approximately 100% yield at approximately 100% purity, as
confirmed by NMR.
Example 3: Preparation of tetraoctylphosphonium
methanesulfonate:
Tetraoctylphosphonium methanesulfonate was prepared
using the method described in Example 1, except that
tetraoctylphosphonium bromide (56.3 g, 0.1 mol),
methanesulfonic acid (redistilled, 9.61 g, 0.1 mol) and
ethanol (5 equivalent, redistilled) were used.
Tetraoctylphosphonium methanesulfonate was obtained
in approximately 100% yield at approximately 100% purity, as
confirmed by NMR.
Example 4: Preparation of tetrabutylphosphonium
D-(+)-camphorsulfonate:
Tetrabutylphosphonium D-(+)-camphorsulfonate was
prepared using the method described in Example 1, except that
D-(+)-camphorsulfonic acid (9.3 g, 0.04 mol) and ethanol (5
equivalent, redistilled) were used.
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Tetrabutylphosphonium D-(+)-camphorsulfonate was
obtained in approximately 100% yield at approximately 100%
purity, as confirmed by NMR.
Example 5: Preparation of tetrapropylammonium
5 methanesulfonate:
Tetrapropylphosphonium methanesulfonate was
prepared using the method described in Example 1, except that
tetrapropylammonium bromide (26.6 g, 0.1 mol),
methanesulfonic acid (redistilled, 9.61 g, 0.1 mol) and
10 ethanol (6 equivalent, redistilled) were used.
Tetrapropylphosphonium methanesulfonate was
obtained in approximately 100% yield at approximately 100%
purity, as confirmed by NMR.
Example 6: Preparation of tetrabutylammonium
15 methanesulfonate:
Tetrabutylammonium methanesulfonate was prepared
using the method described in Example 1, except that
tetrabutylammonium bromide (32.2 g, 0.1 mol), methanesulfonic
acid (redistilled, 9.61 g, 0.1 mol) and ethanol (7
equivalent, redistilled) were used.
Tetrabutylammonium methanesulfonate was obtained in
approximately 100% yield at approximately 100% purity, as
confirmed by NMR.
Example 7: Preparation of N-butylpyridinium methanesulfonate:
N-butylpyridinium methanesulfonate was prepared
using the method described in Example 1, except that
N-butylpyridinium bromide (21.6 g, 0.1 mol), methanesulfonic
acid (redistilled, 9.61 g, 0.1 mol) and ethanol (3
equivalent, redistilled) were used.
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N-butylpyridinium methanesulfonate was obtained in
approximately 100% yield at approximately 100% purity, as
confirmed by NMR.
Example 8: Preparation of 1-propyl-3-methylimidazolium
methanesulfonate:
1-propyl-3-methylimidazolium methanesulfonate was
prepared using the method described in Example 1, except that
1-propyl-3-methylimidazolium bromide (65.6 g, 0.32 mol),
methanesulfonic acid (redistilled, 30.8 g, 0.32 mol) and
propanol (5 equivalent, redistilled) were used.
1-propyl-3-methylimidazolium methanesulfonate was
obtained in approximately 100% yield at approximately 100%
purity, as confirmed by NMR.
Example 9: Preparation of 1-butyl-3-ethylimidazolium
methanesulfonate:
1-butyl-3-ethylimidazolium methanesulfonate was
prepared using the method described in Example 1, except that
1-butyl-3-ethylimidazolium bromide (23.3 g, 0.1 mol),
methanesulfonic acid (redistilled, 9.61 g, 0.1 mol) and
ethanol (6 equivalent, redistilled) were used.
1-butyl-3-ethylimidazolium methanesulfonate was
obtained in approximately 100% yield at approximately 100%
purity, as confirmed by NMR.
Example 10: Preparation of 1-hexyl-3-ethylimidazolium
methanesulfonate:
1-hexyl-3-ethylimidazolium methanesulfonate was
prepared using the method described in Example 1, except that
1-hexyl-3-ethylimidazolium bromide (27.3 g, 0.1 mol),
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methanesulfonic acid (redistilled, 9.61 g, 0.1 mol) and
ethanol (4 equivalent, redistilled) were used.
1=hexyl-3-ethylimidazolium methanesulfonate was
obtained in approximately 100% yield at approximately 100%
purity, as confirmed by NMR.
Example 11: Preparation of 1-butyl-3-ethylimidazolium
DL-camphorsulfonate:
1-butyl-3-ethylimidazolium DL-camphorsulfonate was
prepared using the method described in Example 1, except that
1-butyl-3-ethylimidazolium bromide (46.6 g, 0.2 mol),
DL-camphorsulfonic acid (46.5 g, 0.2 mol) and ethanol (7
equivalent, redistilled) were used.
1-butyl-3-ethylimidazolium DL-camphorsulfonate was
obtained in approximately 100% yield at approximately 100%
purity, as confirmed by NMR.
Experiment 12: Purification of ionic liquid products using
activated charcoal:
A 250 ml round-bottom flask was charged with 50 ml
of 1-butyl-3-ethylimidazolium methanesulfonate (brownish)
obtained in Example 9, 50 ml of ethanol and 20 g of charcoal
(4-20 mesh). The mixture was heated to 50 C and maintained
at this temperature overnight, with stirring. The reaction
mixture was filtered and the filtrate was concentrated by
evaporation under reduced pressure to remove ethanol.
The 1-butyl-3-ethylimidazolium methanesulfonate
(slightly yellowish) was obtained in approximately 100% yield
at approximately 100% purity, as confirmed by NMR.
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Example 13: Preparation of tetrabutylphosphonium
bis(trifluoromethanesulfonyl)imide:
To a 4 dram vial was added tetrabutylphosphonium
bromide (a 71.2% solution in 28.8% of isopropanol, a Cytec
compound CYPHOS 442P; 1.62 g, 0.0034 mol) and
bis(trifluoromethanesulfonyl)imide (0.96 g, 0.0034 mol) at
room temperature with stirring. The mixture was heated using
an oil bath (95 C) to allow 2-bromopropane to evaporate.
AgNO3 test showed absence of bromide anion. Another portion
of isopropanol (0.5 ml, 0.0065 mol) was added to the mixture
and heating was continued overnight to evaporate all
volatiles. Tetrabutylphosphonium
bis(trifluoromoethanesulfonyl)imide was obtained in
approximately 100% yield at approximately 100% purity, as
comfirmed by NMR.
Example 14: Preparation of tetraoctylphosphonium
bis(trifluoromethanesulfonyl)imide:
To a 4 dram vial was added tetraoctylphosphonium
bromide (a Cytec compound CYPHOS 482; 1.69 g, 0.003 mol), 1-
propanol (0.732 g, 0.012 mol) and
bis(trifluoromethanesulfonyl)imide (0.9 g, 0.0031 mol) at
room temperature with stirring. The mixture was heated using
an oil bath (95 C) to allow 1-bromopropane to evaporate.
AgNO3 test showed absence of bromide anion. Another portion
of 1-propanol (0.5 ml, 0.0067 mol) was added to the mixture
and heating was continued overnight to evaporate all
volatiles. Tetraoctylphosphonium
bis(trifluoromoethanesulfonyl)imide was obtained in
approximately 100% yield at approximately 100% purity, as
comfirmed by NMR.
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Example 15: Preparation of tetraoctylphosphonium
bis(trifluoromethanesulfonyl)imide:
To a 4 dram vial was added tetraoctylphosphonium
bromide (a Cytec compound CYPHOS 482; 1.76 g, 0.0031 mol) and
bis(trifluoromethanesulfonyl)imide (0.9 g, 0.0031 mol) at
room temperature with stirring. A stream or propene was
bubbled into the slightly reddish liquefied mixture for 4
hours. NMR showed the formation of 2-bromopropane. All
volatiles were then evaporated off on a rotavapor. AgNO3
test showed absence of bromide anion. Tetraoctylphosphonium
bis(trifluoromoethanesulfonyl)imide was obtained in
approximately 100% yield at approximately 100% purity, as
comfirmed by NMR.
Example 16: Preparation of 1-butyl-3-methylimidazolium
bromide in ethanol:
To a 250 ml flat bottom flask immersed in an
ice-bath was added 1-bromobutane (249 g, 1.82 mol), ethanol
(70 g, 1.52 mol) and 1-methylimidazole (redistilled, 124.5 g,
1.52 mol). The mixture was stirred for 72 hr to provide a
colorless liquid. NMR showed that no 1-methylimidazole
remained in the reaction mixture.
Example 17: Preparation of 1-butyl-3-methylimidazolium
bis(trifluoromethanesulfonyl)imide:
A mixture of 1-butyl-3-methylimidazolium bromide
(0.267 g, 1.22 mmol), methanol (0.047 g, 1.44 mmol) and
bis(trifluoromethanesulfonyl)imide (0.372 g, 1.32 mmol)
sealed in a vial was stirred at room temperature then heated
to 50 C overnight with stirring. The progress of the
reaction was followed with NMR and Mass Spectrophotometry
(MS). When the reaction was completed, volatiles were
removed by evaporation under reduced pressure. The contents
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of the flask were then dried to remove water under reduced
pressure at 60 C.
1-butyl-3-methylimidazolium
bis(trifluoromethanesulfonyl)imide (a colorless liquid) was
5 obtained in approximately 100% yield (0.513 g) at
approximately 100% purity as assessed by NMR and MS.
Example 18: Preparation of 1-butyl-3-methylimidazolium
bis(trifluoromethanesulfonyl)imide:
A mixture of 1-butyl-3-methylimidazolium bromide
10 (0.228 g, 1.05 mmol), isopropanol (0.075 g, 1.26 mmol) and
bis(trifluoromethanesulfonyl)imide (0.322 g, 1.15 mmol) was
sealed in a vial was stirred at room temperature for about 4
hours, then heated to 50 C overnight with stirring. The
reaction was followed by NMR and MS. When the reaction was
15 complete, the reaction mixture was worked up by evaporating
off volatile compounds under reduced pressure. The reaction
mixture was then dried to remove water under reduced pressure
at 60 C.
The product, 1-butyl-3-methylimidazolium
20 bis(trifluoromethanesulfonyl)imide, was obtained as a
colorless liquid in approximately 100% yield (0.438 g) at
approximately 100% purity as determined by NMR and MS.
Example 19. Preparation of 1-butyl-3-methylimidazolium
bis(trifluoromethanesulfonyl)imide:
A mixture of 1-butyl-3-methylimidazolium bromide
(0.285 g, 1.31 mmol), t-butanol (0.116 g, 1.56 mmol) and
bis(trifluoromethanesulfonyl)imide (0.323 g, 1.44 mmol) was
sealed in a vial was stirred at room temperature for 4 hours,
then heated to 50 C overnight with stirring. The reaction
was followed by NMR and MS. When the reaction was completed,
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volatile compouds were removed from the reaction by
evaporation under reduced pressure. The reaction mixture was
further dried to remove water by evaporation under reduced
pressure at 60 C.
The product, 1-butyl-3-methylimidazolium
bis(trifluoromethanesulfonyl)imide, was obtained as a
colorless liquid in approximately 100% yield (0.547 g) at
approximately 100% purity as determined by NMR and MS.
Example 20. Preparation of N-hexyl-3-picolinium
bis(trifluoromethanesulfonyl)imide:
A mixture of N-hexyl-3-picolinium bromide (0.216 g,
0.84 mmol), isopropanol (0.082 g, 1.36 mmol) and
bis(trifluoromethanesulfonyl)imide (0.257 g, 0.92 mmol) was
sealed in a vial and stirred at room temperature for 1 hour,
then heated to 50 C overnight with stirring. The reaction
was followed by NMR and MS. When the reaction was completed,
volatile compounds were removed by evaporation under reduced
pressure. The reaciton mixture was further dried to remove
water under reduced pressure at 60 C.
The product, N-hexyl-3-picolinium
bis(trifluoromethanesulfonyl)imide, was a pale-yellow liquid
obtained in approximately 100% yield (0.383 g) and
approximately 100% purity as determined by NMR and MS.
Example 21. Preparation of N-hexyl-3-picolinium
bis(trifluoromethanesulfonyl)imide:
A mixture of N-hexyl-3-picolinium bromide (0.223 g,
0.86 mmol), t-butanol (0.077 g, 1.04 mmol) and
bis(trifluoromethanesulfonyl)imide (0.265 g, 0.94 mmol)
sealed in a vial was stirred at room temperature for 1 hour,
then heated to 50 C overnight with stirring. The reaction
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was followed by NMR and MS. When the reaction was completed,
volatile compounds were removed from the reaction mixture by
evaporation under reduced pressure. The reaction mixture was
further dried to remove water under reduced pressure at 60 C.
The product, N-hexyl-3-picolinium
bis(trifluoromethanesulfonyl)imide, was a pale-yellow liquid
obtained in approximately 100% yield (0.395 g) and
approximately 100% purity as determined by NMR and MS.
