Synthesis and properties of chiral ammonium-based ionic liquids

Article abstract of DOI:10.1002/chem.200500026

New chiral ammonium-based ionic liquids containing the (1R,2S,5R)-(-)- menthyl group can be easily and efficiently prepared under ambient conditions. The preparation and characterization of trialkyl[(1R,25,5R)-(-)-menthoxymethyl] ammonium salts is reporte

Full text of DOI:10.1002/chem.200500026

FULL PAPER
Synthesis and Properties of Chiral Ammonium-Based Ionic Liquids
Juliusz Pernak* and Joanna Feder-Kubis[a]
Abstract: New chiral ammonium-based
ionic liquids containing the (1R,2S,5R)-
(ꢀ)-menthyl group can be easily and
efficiently prepared under ambient
conditions. The preparation and char-
acterization of trialkyl[(1R,2S,5R)-(ꢀ)-
menthoxymethyl]ammonium salts is re-
ported. The salts have been demon-
strated to be air- and moisture-stable
under ambient conditions and can be
readily used in a variety of standard ex-
The chiral, room-temperature ionic liq-
uids have been characterized by physi-
cal properties such as specific rotation,
density, viscosity, thermal degradation,
and glass transition temperature.
Trialkyl[(1R,2S,5R)-(ꢀ)-menthoxyme-
thyl]ammonium chloride prototype
ionic liquids have also been found to
exhibit strong antimicrobial and high
antielectrostatic activities.
perimental procedures. The single-crys-
tal X-ray structure of butyldimethyl-
[(1R,2S,5R)-(ꢀ)-menthoxymethyl]am-
monium chloride has been determined.
Keywords: ammonium salts · anti-
microbial activity · chirality · green
chemistry · ionic liquids · menthol
Introduction
due to the large number of ILs to choose from, a high po-
tential exists to find the optimum one with satisfactory prop-
erties for a specific application.
Ionic liquids (ILs) open up a wide field for future investiga-
tions in chemistry, electrochemistry, biology, physics, materi-
al science, and medicine. The first IL was prepared almost a
century ago by protonation of ethylamine with nitric acid.[1]
Owing to their unique chemical and physical properties,
these groups of liquids based on organic cations have been
extensively studied over the past few years as neoteric and
“green” solvents. ILs possess a number of interesting prop-
erties, such as their lack of vapor pressure (they cannot con-
tribute to air pollution) and their large liquid range. They
are highly solvating, yet have a noncoordinating nature and
a wide accessible temperature range within which they are
not flammable. They are also compatible with various or-
ganic compounds, organometallic catalysts, and even some
inorganic compounds, and generally can be easily separated
from reaction products. Most importantly, the ionic liquids
can be recycled. A number of excellent articles are already
available wherein the properties and various applications of
these environmentally friendly media have been de-
scribed.[2–10] In recent years, the number of possible cation
and anion combinations has increased significantly and thus,
The newest class of ILs are chiral ionic liquids (CILs).
The method of synthesis of CILs and the investigation of
ILs in the field of chirality have recently been reviewed.[11]
Few CILs have been described and their real potential in
asymmetric synthesis remains to be proven. From a structur-
al point of view, chirality in these salts can arise from either
the anion or the cation. Aprotic and protic ILs in which the
chirality resides in the anion are presented in Scheme 1.
Chiral salts (I) have been successfully used in asymmetric
Diels–Alder reactions.[12] The properties and antimicrobial
activities of protic imidazolium l-lactates (II) have recently
[a] Dr. J. Pernak, J. Feder-Kubis
´
Poznan University of Technology
Department of Chemical Technology
´
pl. Skłodowskiej-Curie 2, 60–965 Poznan (Poland)
Fax : (+61)665-3649
E-mail: juliusz.pernak@put.poznan.pl
Scheme 1. Aprotic and protic imidazolium lactates.
Chem. Eur. J. 2005, 11, 4441– 4449
DOI: 10.1002/chem.200500026
ꢀ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4441

been recognized.[13] In subsequent examples, chirality in the
salts has been introduced by cations such as imidazolium,
been derived from (S)-valine on a multigram scale and thia-
zolium CILs (XIV)[21] have been obtained from amino alco-
hols.
ammonium,
pyridinium,
oxalium,
and
thiazolium
(Scheme 2). The chiral 1,3-dialkylimidazolium bromide III
acts as a Lewis acid in asymmetric Diels–Alder reactions.[14]
Imidazolium salts with planar chirality (IV)[15] and chiral lat-
eral chains (V, VI)[16] and (VII)[17] have also been prepared.
Chiral hydroxyammonium ILs (VIII, IX) derived from
chiral amino alcohols have been obtained on a kilogram
scale,[18] and salts such as X have been produced under sol-
vent-free conditions with the aid of microwave activation.[19]
Pyridinium CILs with axial chirality (XI) have been synthe-
sized through an enantioselective reaction,[11] while other
pyridinium derivatives have the chirality residing in the
alkyl substituent (XII).[20] Oxazolium salts (XIII)[18] have
Entirely new are room-temperature ionic liquids (RTILs)
from natural amino acids. A series of these has been pre-
pared by coupling the imidazolium cation with 20 different
natural amino acids.[22]
Herein, we wish to report the straightforward synthesis of
a novel class of chiral ammonium-based ionic liquids, de-
rived from the “chiral pool”.
Results and Discussion
The
trialkyl[(1R,2S,5R)-(ꢀ)-menthoxymethyl]ammonium
chlorides, which are prototypes of ionic liquids, were pre-
pared by Menschutkin quaternization (Scheme 3). Chloro-
Scheme 3. Preparation of the trialkyl[(1R,2S,5R)-(ꢀ)-menthoxymethyl]-
ammonium chlorides by Menschutkin quaternization.
methyl (1R,2S,5R)-(ꢀ)-menthyl ether was obtained by
chloromethylation of (1R,2S,5R)-(ꢀ)-menthol (Scheme 4).
The (ꢀ)-isomer, a well-known compound, has previously
Scheme 4. Chloromethylation of (1R,2S,5R)-(ꢀ)-menthol.
been prepared in 55% yield[23] by bubbling anhydrous HCl
through a solution of (ꢀ)-menthol and 1,3,5-trioxane in
CH2Cl2 or in 90% yield by carrying out the same reaction in
pentane solution.[24] We have now developed an effective
way to synthesize this ether in up to 90% yield by using
paraformaldehyde with toluene as the solvent.
In the past, chloromethyl (1R,2S,5R)-(ꢀ)-menthyl ether
has been used for the synthesis of diastereomeric formalde-
hyde acetals[23,25,26] and for the protection of a range of
chiral alcohols.[27]
Chloromethyl (1R,2S,5R)-(ꢀ)-menthyl ether is an excel-
lent reagent for quaternization, but it is readily hydrolyzed
to HCl, CH2O, and menthol. In view of this situation, qua-
ternization should be conducted under strictly anhydrous
conditions. This permits a specific type of Menschutkin reac-
Scheme 2. Chiral imidazolium, ammonium, pyridinium, oxazolium, and
thiazolium ILs.
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Chem. Eur. J. 2005, 11, 4441– 4449

Chiral Ammonium-Based Ionic Liquids
FULL PAPER
tion involving an SN1mechanism, giving a very high yield of
96–99%. The initial rate-determining step has been identi-
fied as being the formation of the cation (Scheme 5).
Figure 1. The molecular components of chloride 1e showing the atom-la-
beling scheme. Displacement ellipsoids are drawn at the 30% probability
level and H atoms are shown as spheres of arbitrary radii.
Scheme 5. Menschutkin reaction type 1.
and the numbering scheme of 1e. It is interesting to note
that, to the best of our knowledge, this is the first example
of a structurally characterized trialkyl(alkoxymethyl)ammo-
nium cation of this type. The bond lengths and angles have
typical values. The apparent shortening of the terminal
Table 1lists the chiral ammonium chlorides 1 that have
been prepared by this procedure. They are very hygroscopic,
but are stable in aqueous solution. Some crystalline chlor-
ides such as 1b, 1g, and 1i–1l are very deliquescent, which
has made it difficult to determine their true melting points.
The remaining chlorides are snow-white crystals. In aqueous
solution, they can be assayed by a direct two-phase back ti-
tration according to the EN ISO 2871-1 (2000) norm. The
assays of each product are given in Table 1. Water makes up
the remainder. Specific rotations for all the chlorides are
also presented in Table 1. All these precursors of ILs are
soluble at room temperature in acetone, chloroform, DMF,
THF, methanol, ethanol, 1-propanol, 2-propanol, and water.
Aqueous solutions of chlorides 1 f–1l have been observed to
foam during the dissolution process. At elevated tempera-
tures, the chlorides 1 have been found to dissolve in ethyl
acetate but not in hexane or diethyl ether.
ꢀ
C C single bond in the n-butyl chain is probably an artifact
of the large thermal parameters of the atoms involved.
The conformation of the n-butyl chain can be described
by N-C-C-C and C-C-C-C torsion angles along the chain
of 174.7(5)8 and 106.7(10)8, respectively. The crystal struc-
tures of the ionic liquids characterized to date, for example
imidazolium derivatives, have been found to be mainly de-
termined by the presence of p stacking, weak hydrogen
bonds, or in some cases mainly by the presence of electro-
static anion–cation interactions (e.g., 1-ethyl-2-methyl-3-
benzylimidazolium
bis(trifluoromethylsulfonyl)amide).[28]
The structure of the salt 1e is different because there is no
p-electron system that can interact with other p electrons or
even with CH groups.[29,30] In the crystal structure, the am-
monium cations are seen to create channels parallel to the
two-fold screw axis along the [010] direction, and these
channels are filled by chains
Crystals of chloride 1e suitable for single-crystal X-ray
structural analysis were collected by filtration, washed with
hexane, and air-dried. Figure 1shows the asymmetric unit
made up of chloride anions and
Table 1. Trialkyl[(1R,2S,5R)-(ꢀ)-menthoxymethyl]ammonium chlorides (1).
water molecules. The chain
R1
R2
R3
Yield [%]
M.p. [8C]
Surfactant content [%] Specific rotation[f] [a]D20
structure is maintained by rela-
tively strong and directional
OꢀH···Clꢀ hydrogen bonds (see
Table 2, Figures 2 and 3).
Anion–water chains are con-
nected to the cation scaffold
through electrostatic interac-
1a
1b
1c
1d
1e
1 f
1g
1h
1i
C2H5
C2H5
C2H5
i-C3H7
C4H9
C6H13
C7H15
C8H17
C9H19
C10H21
C11H23
C12H25
C2H5 C2H5
C2H5 CH3
98.0
97.5
99.0
98.5
96.0
97.0
97.0
98.5
97.0
97.0
97.0
97.5
99.0
31–33[a]
hygroscopic
87.5–90[a]
96.5
96.7
97.0
97.9
96.5
97.6
97.9
99.9
99.1
99.8
99.9
99.8
99.0
ꢀ57.4 (c=1.1)
ꢀ59.5 (c=0.7)
ꢀ68.7 (c=0.9)
ꢀ71.3 (c=0.6)
ꢀ64.8 (c=1.1)
ꢀ55.7 (c=0.7)
ꢀ54.1( c=0.7)
ꢀ54.1( c=1.0)
ꢀ50.3 (c=0.5)
ꢀ51.5 (c=1.4)
ꢀ48.8 (c=0.8)
ꢀ48.3 (c=1.5)
ꢀ63.5 (c=1.1)
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
158–161[b]
130–132[c]
113–116[a]
hygroscopic
74–76[d]
ꢀ
tions and weak C H···O and
CꢀH···Clꢀ hydrogen bonds
(Table 2, Figure 2). Similar
water–fluoride anion chains
were found in the structure of
1-butyl-3-methylimidazolium
fluoride.[31]
hygroscopic
hygroscopic
hygroscopic
hygroscopic
126–129[e]
1j
1k
1l
1m CH2Ph CH3
[a] From ethyl acetate; plates. [b] From ethyl acetate/ethanol; plates. [c] From ethyl acetate/acetone; large nee-
dles. [d] From ethyl acetate; needles. [e] From ethyl acetate/chloroform; plates. [f] c in ethanol.
Chem. Eur. J. 2005, 11, 4441– 4449
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ꢀ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4443

J. Pernak and J. Feder-Kubis
Table 2. Selected hydrogen bonds in the crystal structure of chloride 1e.
Donor–H···Acceptor D–H [Š] H···A [Š] D···A [Š] D–H···A [8]
to be fully water-miscible at room temperature. Of the 18
salts prepared, 12 would qualify as ILs (salts that melt at
<1008C). Table 3 contains the melting points, estimated
assays in methanol/chloroform solutions, and specific ro-
tations of 2–7. These salts are insoluble in hexane or di-
ethyl ether, but are soluble in acetone, chloroform, DMF,
THF, ethyl acetate, toluene, and low-molecular-weight alco-
hols.
O2–H21···Cl[a]
0.96
0.88
0.97
0.97
0.97
0.97
0.97
2.27
2.41
2.75
2.53
2.60
2.55
2.76
3.190(4)
3.217(4)
3.655(4)
3.455(6)
3.488(7)
3.501(6)
3.693(5)
160
152
156
159
154
173
162
O2–H22···Cl[b]
C12–H12A···Cl
C12–H12B···O2[c]
C13–H13A···O2[d]
C14–H14B···O2
C15–H15A···Cl[a]
1
Symmetry codes: [a] x, ꢀ1+y, z; [b] ꢀx, ꢀ = +y, 1= ꢀz; [c] 1ꢀx, 1= +y,
On the other hand, RTILs can be obtained by changing
the chloride anion to [Tf2N]. Table 4 lists 13 [Tf2N] (8) salts,
including 10 which represent RTILs. All of the RTILs are
colorless liquids, and are nonvolatile, nonflammable, and
miscible with acetone, chloroform, ethyl acetate, DMF,
THF, toluene, and low-molecular-weight alcohols. They are
insoluble in hexane and diethyl ether, and are miscible with
water. They are stable in air, in contact with water, and in
commonly used organic solvents.
2
2
2
1
1= ꢀz; [d] ꢀx, 1= +y, = ꢀz.
2
2
2
1
The salts were characterized by H and 13C NMR analyses
and by elemental analysis. Comparison of the 1H NMR
spectra of the chlorides 1 with those of the salts 2–8 indicat-
ed differences in the proton chemical shifts, as listed in
Table 5. These shift differences were observed most promi-
nently in four functional groups: N+CH2O, OCH(menthyl-
C6), N+CH2R1, and N+(CH3)2. The substitution of the small
[Cl] anion with the larger [Tf2N] or [PF6] resulted in proton-
shift differences of as much as 0.43 ppm. The 13C NMR spec-
tra of salts 1–8 indicated no significant variations in the
carbon-signal shifts.
Figure 2. The packing scheme of chloride 1e as seen approximately along
the [100] direction. Hydrogen bonds are depicted as dashed lines.
The RTILs can be made anhydrous by heating them at
808C in vacuo and storing them over P4O10. The water con-
tent was determined to be less than 500 ppm by coulometric
Karl–Fischer titration. After 30 days, these anhydrous liq-
uids were found to have absorbed water from the atmos-
phere to a level of 1.4%. From this observation, we assume
that the solubility of water in these ILs does not exceed
1.5%. On the other hand, the solubility of the ILs in water
was found to be low, comparable to that of
[methyltributylammonium][Tf2N], 0.7 gLꢀ1.[32] The hydro-
phobic character of these RTILs is imparted by the [Tf2N]
anion, which is responsible for interactions between water
and the IL. Water interacts strongly with the anions and the
strength of the interactions is dependent on the nature of
the anions.[33] The low water content measured is of impor-
tance for future applications. Removal of chloride ions from
the hydrophobic ILs has been demonstrated by rinsing them
with distilled water. The specific rotations, densities, viscosi-
ties, thermal degradation temperatures, and glass transition
temperatures for anhydrous and chloride-free RTILs have
been measured. The results are presented in Table 4. The
CILs are more dense than water (1.25 to 1.14 gmLꢀ1). As a
general conclusion, it can be stated that elongation of the
alkyl substituent leads to a concomitant linear decrease in
density. The densities of the ILs are temperature dependent.
As the temperature is varied from 30 to 408C, the density
decreases by about 3%. ILs are inherently much more vis-
cous than common organic solvents and the viscosities vary
in the range from 10 to 1000 mPas at room temperature.[10]
Figure 3. Space-filling model of the cationic crystal structure of 1e as
seen along the [010] direction (after removal of chloride anions and
water molecules). The channels that can be filled by anion–water poly-
1
3
meric chains are seen along a 21 screw axis at (0, y, = ) and (1= , y, = ).
4
2
4
The nine black spheres represent oxygen.
The final step of the synthesis involved metathesis of the
chlorides with an appropriate inorganic salt in a water/meth-
anol solution. The ion-exchange reaction proceeded smooth-
ly, with the efficiency usually exceeding 90%. All of the
[BF4] (2), [ClO4] (3), [I] (4), [PF6] (5), and [CF3COO] (6)
salts with 1 were obtained as solids and could be easily crys-
tallized from ethanol/water solution to form white plates
with sharp melting points. Salts 2–5 were found to be insolu-
ble in water. Thus, by changing the counteranion, hydrophil-
ic chlorides are transformed to hydrophobic salts. We also
obtained acesulfamates (7) in the form of oils, which proved
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Chiral Ammonium-Based Ionic Liquids
FULL PAPER
Table 3. Trialkyl[(1R,2S,5S)-(ꢀ)-menthoxymethyl]ammonium salts (2–7).
crease in the molar heat capaci-
ty associated with the glass
transition. They form glasses
for which the glass transition
temperatures are very low (ap-
Salt
R1
R2
R3
Anion
Yield
M.p.
Surfactant
content [%]
Specific rotation[b]
[%]
[8C]
[a]2D0
ꢀ
2a
2b
2c
2d
2e
2 f
2g
2h
2i
2j
2k
2l
2m
3
C2H5
C2H5
C2H5
i-C3H7
C4H9
C6H13
C7H15
C8H17
C9H19
C10H21
C11H23
C12H25
CH2Ph
C4H9
C2H5
C2H5
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
C2H5
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
BF4ꢀ
99.5
99.0
99.0
99.0
98.5
99.0
99.5
99.0
99.5
99.5
99.5
99.5
99.5
99.0
99.5
99.0
89.0
91.5
125–126.5
150.5–152
161.5–164
203–206
68.5–7197.7
42–44
69–72
87.5–88.5
69–72
99.8
99.5
98.9
98.5
ꢀ64.8 (c=0.4)
ꢀ61.5 (c=1.0)
ꢀ63.5 (c=1.0)
ꢀ61.2 (c=0.8)
ꢀ58.3 (c=1.1)
ꢀ52.7 (c=1.0)
ꢀ49.1( c=1.0)
ꢀ48.9 (c=1.4)
ꢀ47.3 (c=1.0)
ꢀ44.8 (c=1.0)
ꢀ44.4 (c=1.0)
ꢀ38.4 (c=1.0)
ꢀ58.2 (c=1.0)
ꢀ56.4 (c=0.9)
ꢀ51.3 (c=0.9)
ꢀ51.6 (c=1.1)
ꢀ52.8 (c=1.1)
ꢀ51.2 (c=0.4)
BF4ꢀ
BF4ꢀ
BF4ꢀ
BF4ꢀ
BF4ꢀ
BF4ꢀ
BF4ꢀ
BF4ꢀ
BF4ꢀ
BF4ꢀ
BF4ꢀ
BF4
proximately
ꢀ508C).
The
change in heat capacity, DCp,
when the sample is heated from
the glass state to the metastable
supercooled liquid, has values
between 0.38 and 0.24 Jgꢀ1 Kꢀ1.
The antielectrostatic effect
was determined according to
the criteria listed in Table 6.
The antielectrostatic effect of
salts 1–8 reflects two quantities:
the surface resistance and the
half-charge decay time. The sur-
face resistance RS (in W) has
been calculated from Equa-
tion (1):
99.7
99.5
98.7
99.9
98.5
99.1
99.9
98.5
98.1
98.9
97.75
98.5
99.9
55–58
43–48
42.5–43
97.5–100
77–78.5
81–83
103–105
72–74
ꢀ
ClO4
4
5
6
7
C4H9
C4H9
C4H9
C4H9
Iꢀ
PF6
ꢀ
CF3COOꢀ
Ace[a]
oil
[a] Acesulfamate. [b] c in ethanol.
The estimated viscosities indicate that the new ILs are
highly viscous. The viscosity is strongly influenced by tem-
perature and the presence of water or organic solvents. In
the case of 8g, increasing the temperature from 358C to 40,
45, 50, 55, and 608C was found to be accompanied by a 145,
200, 280, 380, 490, and 600% decrease in viscosity, respec-
tively, based on the absolute value of 130 mPas. The de-
pendence of viscosity upon temperature and cosolvents is
dramatic, which is in line with earlier data.[34]
All RTILs show no measurable vapor pressure. The esti-
mated thermal-degradation temperature is used to define
the upper temperature limit at which the CILs can be used.
Below this temperature, no alterations in liquid color have
been observed. The limit of the liquid range of a given
RTIL can be higher by about 408C if the thermogravimetric
analysis (TGA) onset temperature is used as an indication.
The DSC thermograms of the RTILs exhibited a single
signal. This indicates that the RTILs show an abrupt in-
Ul
is
ð1Þ
RS ¼
in which U is the applied voltage (U=100 V), l is the length
of the electrode (l=100 mm), i is the measured current in-
tensity, and s is the distance between the electrodes (s=
10 mm). The half-charge decay time (in seconds) has been
calculated according to Equation (2):
rffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
t2þ þ t2ꢀ
ð2Þ
t=
1
¼
2
2
in which t+ and t are the mean half-decay times of positive
and negative charges, respectively. The results are presented
in Table 7. All chlorides and [Tf2N] salts show excellent anti-
ꢀ
Table 4. Chiral ammonium-based ionic liquids (8).
[f]
[g]
CIL R1
R2
R3
Anion
Yield
[%]
Specific rotation[d]
Density[e]
Viscosity[e]
[mPas]
Tg
Glass transition
DCp
[a]2D0
[gmLꢀ1
]
[8C]
[8C]
[Jgꢀ1 Kꢀ1
]
8a
8b
8c
C2H5
C2H5
C2H5
C2H5 C2H5 Tf2N
85.5
94.5
89.0
99.0
87.5
84.5
89.5
93.5
95.0
91.0
92.5
99.5
99.0
ꢀ38.6 (c=1.4)
ꢀ39.1( c=1.2)
ꢀ40.6 (c=1.1)
ꢀ39.5 (c=1.1)
ꢀ38.2 (c=0.9)
ꢀ41.6 (c=1.0)
ꢀ34.8 (c=1.2)
ꢀ35.6 (c=1.4)
ꢀ33.2 (c=1.4)
ꢀ37.8 (c=1.1)
ꢀ32.7 (c=1.6)
ꢀ31.5 (c=1.2)
ꢀ39.1( c=1.0)
1.25
1.26
1.27
–
1.24
1.21
1.19
1.18
1.17
1.15
1.14
–
876
754
714
–
745
774
787
806
829
840
844
–
179
197
199
–
200
200
202
200
199
200
206
–
ꢀ45.8
ꢀ48.5
ꢀ49.9
–
ꢀ50.10.28
ꢀ50.2
ꢀ52.8
ꢀ53.0
ꢀ53.2
ꢀ54.4
ꢀ54.3
–
0.38
0.30
0.24
–
C2H5 CH3
CH3 CH3
Tf2N
Tf2N
Tf2N
Tf2N
Tf2N
Tf2N
Tf2N
Tf2N
Tf2N
Tf2N
Tf2N
Tf2N
8d[a] i-C3H7 CH3 CH3
8e
8 f
8g
8h
8i
C4H9
CH3 CH3
C6H13 CH3 CH3
C7H15 CH3 CH3
C8H17 CH3 CH3
C9H19 CH3 CH3
C10H21 CH3 CH3
C11H23 CH3 CH3
0.29
0.32
0.32
0.31
0.30
0.30
–
8j
8k
8l[b] C12H25 CH3 CH3
8m[c] CH2Ph CH3 CH3
–
–
–
–
–
[a] M.p. 40–428C; plates. [b] M.p. 28–308C; plates. [c] M.p. 46–488C; plates. [d] c in ethanol. [e] At 308C. [f] Thermal degradation temperature. [g] Heat
capacity jump.
Chem. Eur. J. 2005, 11, 4441– 4449
www.chemeurj.org
ꢀ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4445

J. Pernak and J. Feder-Kubis
Table 5. The shifts in proton signals.[a]
to that of the known antistatic
agent Catanac 609 (N,N-bis(2-
hydroxyethyl)-N-(3’-dodecyl-
oxy-2’-hydroxypropyl)methyl-
Salt
Anion
Functional group
OCH-(menthyl-C6)
N+CH2O[b]
N+CH2R1
3.51(m)
N+(CH3)2
1e
2e
Clꢀ
4.98 (d, J=6.9)
4.94 (d, J=6.9)
4.62 (d, J=7.1)
4.58 (d, J=6.9)
4.65 (t, J=7.5)
5.03 (d, J=6.9)
4.93 (d, J=6.9)
4.56 (d, J=7.1)
4.51(d, J=6.9)
4.79 (t, J=7.7)
3.59 (td)
3.36 (s)
3.37 (s)
3.07 (s)
ammonium
methanesulfate;
ꢀ
BF4
3.52 (td)
3.29 (m)
1
logRS =8.48, t = =0.25 s). Re-
2
ꢀ
cently, imidazolium ILs have
been found to represent effec-
tive antielectrostatic agents for
pine and maple.[35]
Biological activities have
been estimated for all of the
chlorides. Minimum inhibitory
concentration (MIC) values and
minimum bactericidal or fungi-
cidal concentration (MBC)
values are provided in Table 8.
Additionally, MIC and MBC
values are presented for benzal-
3
4
ClO4
3.54 (td)
3.65 (m)
3.32 (m)
3.57 (m)
3.11 (s)
3.35 (s)
3.36 (s)
3.02 (s)
Iꢀ
ꢀ
5
PF6
3.49 (td)
3.5 (td)
3.18 (m)
3.34 (m)
3.33 (m)
3.24 (m)
6
CF3COOꢀ
Aceꢀ[c]
3.20 (s)
3.21(s)
3.17 (s)
7
4.75 (d, J=7.4)
4.72 (d, J=7.1)
4.57 (d, J=6.9)
4.51(d, J=6.9)
3.55 (td)
3.49 (td)
8e
Tf2Nꢀ
3.01(s)
[a] Shifts in ppm. [b] J in Hz. [c] Acesulfamate.
Table 6. Criteria for the estimation of the antielectrostatic effect based
konium chloride (BAC, in which “alkyl” represents a mix-
ture of alkyls ranging from C8H17 to C18H37). Chlorides bear-
ing an alkyl group containing more than five carbon atoms
can be regarded as active. Relationships between mean MIC
and MBC values for the studied microbes and the number
of carbon atoms in the alkyl group are presented in
Figure 4. The activity is seen to be related to the length of
the alkyl substituent and thus to molecular mass. The curves
demonstrate optimum antimicrobial efficiency. The chloride
1k, containing an undecyl substituent, can be regarded as
being the most active against cocci, rods, fungi, and bacillus,
exhibiting higher efficiency than that of commercially avail-
able BAC. Chlorides 1d, 1e, and 1m demonstrated low ac-
tivity against some microbes. Chlorides 1a–1c, on the other
hand, were found to be practically inactive. Since [Tf2N]
salts are insoluble in water, their MIC and MBC values
could not be estimated. With reference to our earlier publi-
cation on the antimicrobial activities of ILs,[36] the [Tf2N]
salts could be expected to show similar activity to that of
the chlorides. If the application of ILs in biochemical proc-
esses is considered, selection of a biologically active solvent
may prove fatal to organisms. It should be kept in mind that
the quaternary nitrogen atom in these ammonium salts is an
essential component in relation to multiple biological activi-
ties.
1
on the surface resistance RS [W] and half-charge decay time t = [s].
2
1
logRS
t =
Antielectrostatic effect
2
<9
<0.5
excellent
9–9.99
10–10.99
11–11.99
12–12.99
>13
0.51–2
2.1–10
10.1–100
>100
very good
good
sufficient
insufficient
>600
lack of antielectrostatic properties
1
Table 7. Surface resistance RS [W], half-charge decay time t = [s], and an-
2
tielectrostatic effects of the prepared salts.
1
t =
1
t =
2
Salt logRS
Effect
Salt logRS
Effect
2
1a
1b
1c
1d
1e
1 f
1g
1h
1i
8.7
7.5
8.3
8.0
7.5
7.3
7.6
8.7
7.7
7.0
7.5
7.8
8.3
>13
>13
12.7
>13
>13
11.5
11.0
12.0
0.2 excellent
<0.1excellent
<0.1excellent
0.3 excellent
<0.1excellent
<0.1excellent
<0.1excellent
<0.1excellent
<0.1excellent
<0.1excellent
<0.1excellent
<0.1excellent
<0.1excellent
>600 lack
>600 lack
>100 insufficient 8h
>600 lack
>600 lack
25 sufficient
55 sufficient
>100 insufficient 8m
2i
2j
2k
2l
2m
3
11.3
11.0
11.5
>13
>13
>13
9.6
>13
8.0
8.3
8.5
8.8
8.9
8.6
8.9
8.0
8.3
8.0
88 sufficient
45 sufficient
25 sufficient
>600 lack
>600 lack
>600 lack
0.25 very good
>600 lack
4
5
8a
8b
8c
8d
8e
8 f
8g
0.3 excellent
0.45 excellent
0.3 excellent
0.3 excellent
0.35 excellent
0.2 excellent
0.25 excellent
0.25 excellent
0.2 excellent
0.25 excellent
0.4 excellent
0.2 excellent
0.2 excellent
1j
1k
1l
1m
2a
2b
2c
2d
2e
2 f
2g
2h
8i
8j
8k
8l
Conclusion
8.8
8.7
8.5
All of the prepared chiral quaternary ammonium salts are
air- and moisture-stable under ambient conditions and may
be handled under a variety of standard experimental condi-
tions. Trialkyl[(1R,2S,5R)-(ꢀ)-menthoxymethyl]ammonium
chlorides with more than five carbon atoms in the alkyl
group exhibit a wide range of antimicrobial activities. The
nature of the anion determines the consistency and hygro-
scopic character of the salt. Salts with the [Tf2N] anion are
RTILs. The important attributes of the CILs include negligi-
electrostatic effects. On the other hand, the [BF4], [ClO4],
and [PF6] salts show a reduced capacity to drain surface
electric charge. [Tf2N] salts penetrate the polymer surface
because they have unique solvation properties and are more
able to disperse the electric charge. Their activity is similar
4446
ꢀ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
Chem. Eur. J. 2005, 11, 4441– 4449

Chiral Ammonium-Based Ionic Liquids
FULL PAPER
Table 8. MIC and MBC values[a] of trialkyl[(1R,2S,5R)-(ꢀ)-menthoxymethyl]ammonium chlorides (1).
Strain
Chlorides
1a
26
52
818
>1637
409
1637
1b
106
213
429
>1715
213
>1715
>1715
>1715
213
1c
112
450
1802
1802
450
1d
55
213
858
>1715
429
>1715
>1715
>1715
213
1e
26
52
409
>1637
409
1637
818
1637
818
1637
>1637
>1637
>1637
>1637
>1637
>1637
818
1 f
1g
1h
1i
1j
1k
1l
1m
121
183
183
1473
47
183
BAC[b]
M. luteus
S. aureua
MIC
MBC
MIC
MBC
6
5.8
89
11
89
5.8
46
2.8
44
2.8
22
1.4
5.5
5.5
86
2.8
5.5
<0.3
21
<0.3
2.6
0.5
2.6
<0.3
2.6
0.5
10
1.3
2.6
159
159
41
<0.25
1.2
0.5
2.4
1.2
4.8
0.5
4.8
0.5
19
1.4
11
2.8
23
1.4
5.6
5.6
23
2.8
2.8
175
175
88
186
24
375
12
93
48
375
12
12
1.3
5.3
1.3
2.7
1.3
21.0
1.3
1.3
165
165
82
0.5
10
<0.25
2.5
<0.25
4.9
S. epidermidis MIC
MBC
1802
E. faecium
E. coli
MIC
MBC
MIC
MBC
MIC
MBC
MIC
MBC
MIC
MBC
MIC
MBC
MIC
MBC
MIC
MBC
MIC
MBC
818
>1637
818
>1802
>1802
450
11
736
>1473
47
178
5.8
5.8
2.5
4.9
0.5
1.2
1637
213
450
213
91
S. marcescens
P. vulgaris
P. aeruginosa
B. subtilis
>1637
>1637
>1637
>1637
>1637
>1637
1637
1637
409
409
>1715
>1715
>1715
>1715
>1715
>1715
213
1715
213
858
>1802
>1802
>1802
>1802
>1802
>1802
>1802
>1802
1802
>1802
>1802
>1802
>1802
>1802
>1715
>1715
>1715
>1715
>1715
>1715
1715
1715
429
429
1499 1439 691
>1499 1439 691
154 299
154 599
10
40
40
1473
>1473
>1473
>1473
>1473
>1473
183
183
47
183
1473
1473
736
750
1499
1499
360 171
719 346
719 171
19
38
38
82
82
41
41
80
88
175
175
2.8
2.8
0.6
1.4
11
88
23
88
1499 1439 346
165
0.5
1.3
0.5
0.5
11
21
11
21
77 148
<0.25
12
24
24
23
23
5.8
46
178
178
89
5.5
5.5
2.8
11
44
86
0.5
1.3
0.5
0.5
5.1
5.1
2.6
5.1
1.2
1.2
0.5
1.2
2.4
9.6
2.4
38
818
409
409
<0.25
<0.25
<0.25
<0.25
1.3
M. catarrhalis
C. albicans
R. rubra
24
>1637
>1637
>1637
>1637
>1715
>1715
>1715
>1715
>1715
>1715
>1715
>1715
>1637
>1637
>1637
>1637
375
375
375
750
22
2.5
4.9
360 171
1473
[a] In mm. [b] Benzalkonium chloride.
Experimental Section
General: 1H NMR spectra were recorded on a Mercury Gemini 300 spec-
trometer at 300 MHz with tetramethylsilane as the standard; 13C NMR
spectra were recorded on the same instrument at 75 MHz. Two-dimen-
sional spectra were obtained using standard pulse sequences from the
Bruker DRX pulse library at 600 MHz.
Elemental analyses were performed at the A. Mickiewicz University,
´
Poznan. Melting points were determined using a model JA 9100 electro-
thermal digital melting-point apparatus. A Mettler Toledo DA 110 M
scale was used for the mass/density measurements. A micro Ostwald vis-
cometer was used for viscosity measurements. Thermal degradation tem-
peratures were determined using a Büchi model B-545 automatic appara-
tus. Optical rotations were measured with a Perkin–Elmer 243B polarim-
eter. Glass transition temperatures were determined using a Perkin–
Elmer differential scanning calorimeter. The instrument temperature
scale was calibrated at the crystal–crystal transition of cyclopentane
(ꢀ151.168C) and the melting point of indium (+156.68C). Samples were
sealed in aluminum pans and scanned at a rate of 20 Kminꢀ1 in a helium
atmosphere.
Preparation of chloromethyl (1R,2S,5R)-(ꢀ)-menthyl ether: Gaseous hy-
drogen chloride was introduced into a mixture of (1R,2S,5R)-(ꢀ)-men-
thol (100 g, 0.64 mol), toluene (200 mL), and paraformaldehyde (19.5 g,
0.65 mol) with efficient mechanical stirring until the solution was saturat-
ed (5 h). The reaction was carried out under isothermal conditions at
108C. Water was removed and an emulsion of reaction-generated water
in the organic phase was obtained, which was then dried over magnesium
sulfate and concentrated under reduced pressure. Hydrogen chloride ab-
sorbed in the reaction product was stripped off with dry nitrogen.
Figure 4. Mean MIC values (top) and MBC values (bottom) for microor-
ganisms.
The amount of chloromethyl (1R,2S,5R)-(ꢀ)-menthyl ether in the final
product was determined by an alkalimetric method: 1g of crude product
was added to 10 mL of acetone at ꢀ208C. HCl absorbed on the substrate
was quickly neutralized with 0.02m KOH in MeOH. Then, hot water
(5 mL) was added. HCl as a product of ether hydrolysis was neutralized
with 0.2m KOH in MeOH.
ble vapor pressure, compatibility with various organic com-
pounds, ease of separation in aqueous/ionic liquid extrac-
tions, antielectrostatic activities, and their potential applica-
tion in asymmetric synthesis.
The crude product contained 92% of chloromethyl (1R,2S,5R)-(ꢀ)-
menthyl ether. This was purified by vacuum distillation to give a clear
Chem. Eur. J. 2005, 11, 4441– 4449
www.chemeurj.org
ꢀ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4447

J. Pernak and J. Feder-Kubis
liquid with boiling point 1088C at 16 mmHg (lit.: 82–848C at
0.8 mmHg[22] or 628C at 0.1mmHg [23]).
(C17), 20.8 (C1), 21.8 (C9 or C10), 22.5 (C4), 24.2 (C16), 25.6 (C8), 30.9
(C2), 33.7 (C3), 40.4 (C7), 47.9 (C5, C13 or C14), 61.1 (C15), 81.4 (C6),
87.6 ppm (C12); elemental analysis calcd (%) for C17H36NOI (397.4): C
51.38, H 9.13, N 3.52; found: C 51.73, H 9.01, N 3.73.
General procedure for Menschutkin quaternization: All reactions were
performed under anhydrous conditions. A solution of freshly distilled tri-
alkylamine (0.036 mol) in hexane (30 mL) was prepared. Chloromethyl
(1R,2S,5R)-(ꢀ)-menthyl ether (7.36 g, 0.036 mol) was slowly added and
the resulting mixture was vigorously stirred for 30 min at room tempera-
ture. The white precipitate produced was removed by filtration and the
filter cake was washed with hexane. The crude product was recrystallized
from either ethyl acetate, ethyl acetate/ethanol, ethyl acetate/acetone, or
ethyl acetate/chloroform. The product was dried under reduced pressure
overnight.
Butyldimethyl[(1R,2S,5R)-(ꢀ)-menthoxymethyl]ammonium hexafluoro-
phosphate (5): 1H NMR (CDCl3, 258C): d=0.79 (d, J=6.9 Hz, 3H; H9
or H10), 0.94 (m, 12H; Ha-3, H1, H9 or H10, Ha-7, Ha-4, H18), 1.37 (m,
4H; H2, H5, H17), 1.67 (m, 4H; Hb-3, Hb-4, H16), 2.47 (m, 2H; Hb-7,
H8), 3.02 (s, 6H; H13, H14), 3.18 (m, 2H; H15), 3.49 (td, J=10.7, J=
4.4 Hz, 1H; H6), 4.51, 4.56 ppm (d, J=6.9, J=7.1Hz, 2H; AB system);
13C NMR (CDCl3): d=13.5 (C18), 15.8 (C9 or C10), 19.6 (C17), 21.1
(C1), 22.0 (C9 or C10), 22.8 (C4), 24.1 (C16), 25.9 (C8), 31.2 (C2), 34.0
(C3), 40.2 (C7), 47.6 (C13 or C14), 47.7 (C13 or C14), 48.1 (C5), 61.3
(C15), 81.8 (C6), 87.8 ppm (C12); elemental analysis calcd (%) for
C17H36NOPF6 (415.4): C 49.15, H 8.73, N 3.37; found: C 48.81, H 8.93, N
3.01.
Butyldimethyl[(1R,2S,5R)-(ꢀ)-menthoxymethyl]ammonium
chloride
(1e): 1H NMR (2D spectra) (CDCl3, 258C): d=0.81(d, J=6.9 Hz, 3H;
H9 or H10), 0.86 (td, J=12.4, J=3.1Hz, 1H; Ha-3), 0.92 (d, J=6.5 Hz,
3H; H1), 0.93 (d, J=6.9 Hz, 3H; H9 or H10), 0.95 (m, 1H; Ha-7), 0.98
(m, 1H; Ha-4), 0.99 (t, J=7.4 Hz, 3H; H18), 1.32 (m, 1H; H5), 1.42 (m,
1H; H2), 1.42 (m, 2H; H17), 1.65 (m, 1H; Hb-4), 1.67 (m, 1H; Hb-3),
1.68 (m, 2H; H16), 2.07 (sept d, J=6.9, J=2.4 Hz, 1H; H8), 2.18 (d, J=
11.7 Hz, 1H; Hb-7), 3.36 (s, 3H; H13 or H14), 3.37 (s, 3H; H13 or H14),
3.51(m, 2H; H15), 3.59 (td, J=10.6, J=4.2 Hz, 1H; H6), 4.98, 4.94 ppm
(d, J=6.9 Hz, 2H; AB system); 13C NMR (CDCl3): d=13.4 (C18), 15.7
(C9 or C10), 19.4 (C17), 20.7 (C1), 21.8 (C9 or C10), 22.4 (C4), 24.0
(C16), 25.5 (C8), 30.9 (C2), 33.7 (C3), 40.3 (C7), 47.5 (C13 or C14), 47.6
(C13 or C14), 47.9 (C5), 60.7 (C15), 81.2 (C6), 87.3 ppm (C12); elemental
analysis calcd (%) for C17H36NClO (305.5): C 66.74, H 11.86, N 4.58;
found: C 66.93, H 11.99, N 4.31.
Butyldimethyl[(1R,2S,5R)-(ꢀ)-menthoxymethyl]ammonium trifluoroace-
tate (6): 1H NMR (CDCl3, 258C): d=0.79 (d, J=6.9 Hz, 3H; H9 or
H10), 0.94 (m, 12H; Ha-3, H1, H9 or H10, Ha-7, Ha-4, H18), 1.37 (m,
4H; H2, H5, H17), 1.67 (m, 4H; Hb-3, Hb-4, H16), 2.48 (m, 2H; Hb-7,
H8), 3.20 (s, 3H; H13 or H14), 3.21 (s, 3H; H13 or H14), 3.34 (m, 2H;
H15), 3.51 (td, J=10.7, J=4.1Hz, 1H; H6), 4.79 ppm (t, J=7.8 Hz, 2H;
H12); 13C NMR (CDCl3): d=13.4 (C18), 15.6 (C9 or C10), 19.5 (C17),
20.9 (C1), 21.8 (C9 or C10), 22.4 (C4), 24.1 (C16), 25.7 (C8), 31.0 (C2),
33.8 (C3), 40.3 (C7), 47.3 (C13 or C14), 47.4 (C13 or C14), 48.0 (C5), 60.9
(C15), 81.5 (C6), 87.6 ppm (C12), anion: 115.3, 119.2, 160.0, 160.4, 160.9,
161.3 ppm; elemental analysis calcd (%) for C19H36F3NO3 (383.5): C
59.51, H 9.46, N 3.65; found: C 59.19, H 9.23, N 3.74.
Preparation of trialkyl[(1R,2S,5R)-(ꢀ)-menthoxymethyl]ammonium salts
(2–8): A solution of the requisite ammonium chloride (1) in either water
(15 mL) (with 1a–1e) or methanol (20 mL) (with 1 f–1l) was added to a
Butyldimethyl[(1R,2S,5R)-(ꢀ)-menthoxymethyl]ammonium
acesulfa-
mate (7): 1H NMR (CDCl3, 258C): d=0.79 (d, J=6.9 Hz, 3H; H9 or
H10), 0.96 (m, 12H; Ha-3, H1, H9 or H10, Ha-7, Ha-4, H18), 1.37 (m,
4H; H2, H5, H17), 1.71 (m, 4H; Hb-3, Hb-4, H16), 2.09 (m, 5H; Hb-7,
H8, and anion), 3.17 (s, 6H; H13, H14), 3.33 (m, 2H; H15), 3.55 (td, J=
10.7, J=4.4 Hz, 1H; H6), 4.72, 4.75 (d, J=7.1, J=7.4 Hz, 2H; AB
system), 5.44 ppm (d, J=1.1 Hz, 1H; anion); 13C NMR (CDCl3): d=13.3
(C18), 15.6 (C9 or C10), 19.4 (anion), 19.7 (C17), 20.8 (C1), 21.8 (C9 or
C10), 22.4 (C4), 24.0 (C16), 25.5 (C8), 30.9 (C2), 33.8 (C3), 40.2 (C7),
47.4 (C13 or C14), 47.5 (C13 or C14), 47.8 (C5), 60.8 (C15), 81.3 (C6),
87.5 ppm (C12), anion: 102.1, 160.5, 169.3 ppm; elemental analysis calcd
(%) for C21H40N2O5S (432.6): C 58.39, H 9.32, N 6.48; found: C 58.76, H
9.61, N 6.56.
stoichiometric amount of
a saturated aqueous solution of NaBF4,
NaClO4, KI, KPF6, CF3COONa, Tf2NLi, or acesulfame-K. The reaction
solution was stirred at room temperature for 2 h. After separation of the
phases, the aqueous phase was decanted and the salt obtained was
washed with cold, distilled water until chloride ions were no longer de-
tected using AgNO3. The crude product that solidified upon cold storage
was recrystallized from ethanol/water. Liquids were dried for 10 h at
808C in vacuo (8 mmHg).
Butyldimethyl[(1R,2S,5R)-(ꢀ)-menthoxymethyl]ammonium tetrafluoro-
borate (2e): 1H NMR (CDCl3, 258C): d=0.79 (d, J=6.9 Hz, 3H; H9 or
H10), 0.92 (m, 12H; Ha-3, H1, H9 or H10, Ha-7, Ha-4, H18), 1.38 (m,
4H; H2, H5, H17), 1.68 (m, 4H; Hb-3, Hb-4, H16), 2.07 (m, 2H; Hb-7,
H8), 3.07 (s, 6H; H13, H14), 3.29 (m, 2H; H15), 3.52 (td, J=10.4, J=
4.1Hz, 1H; H6), 4.58, 4.62 ppm (d, J=6.9, J=7.1Hz, 2H; AB system);
13C NMR (CDCl3): d=13.4 (C18), 15.6 (C9 or C10), 19.5 (C17), 20.9
(C1), 21.9 (C9 or C10), 22.6 (C4), 24.0 (C16), 25.7 (C8), 31.1 (C2), 33.9
(C3), 40.2 (C7), 47.4 (C13 or C14), 47.5 (C13 or C14), 48.1 (C5), 61.1
(C15), 81.6 (C6), 87.7 ppm (C12); elemental analysis calcd (%) for
C17H36NOBF4 (357.3): C 57.10, H 10.15, N 3.92; found: C 56.92, H 9.83,
N 3.88.
Butyldimethyl[(1R,2S,5R)-(ꢀ)-menthoxymethyl]ammonium bis(trifluoro-
methanesulfonyl)imide (8e): 1H NMR (CDCl3, 258C): d=0.78 (d, J=
6.9 Hz, 3H; H9 or H10), 0.95 (m, 12H; Ha-3, H1, H9 or H10, Ha-7, Ha-
4, H18), 1.37 (m, 4H; H2, H5, H17), 1.67 (m, 4H; Hb-3, Hb-4, H16),
2.47 (m, 2H; Hb-7, H8), 3.01 (s, 6H; H13, H14), 3.24 (m, 2H; H15), 3.49
(td, J=10.7, J=4.4 Hz, 1H; H6), 4.51, 4.57 ppm (d, J=6.9, J=7.1Hz,
2H; AB system); 13C NMR (CDCl3): d=13.3 (C18), 15.5 (C9 or C10),
19.4 (C17), 20.9 (C1), 21.8 (C9 or C10), 22.6 (C4), 24.0 (C16), 25.7 (C8),
31.0 (C2), 33.9 (C3), 40.1 (C7), 47.5 (C13 or C14), 47.7 (C13 or C14), 47.9
(C5), 61.3 (C15), 81.5 (C6), 87.9 ppm (C12), anion: 113.6, 117.5, 121.7,
126.0 ppm; elemental analysis calcd (%) for C19H36N2F6O5S2 (550.6): C
41.45, H 6.59, N 5.09; found: C 41.25, H 6.39, N 5.01.
Butyldimethyl[(1R,2S,5R)-(ꢀ)-menthoxymethyl]ammonium perchlorate
(3): 1H NMR (CDCl3, 258C): d=0.80 (d, J=6.9 Hz, 3H; H9 or H10),
0.96 (m, 12H; Ha-3, H1, H9 or H10, Ha-7, Ha-4, H18), 1.38 (m, 4H; H2,
H5, H17), 1.69 (m, 4H; Hb-3, Hb-4, H16), 2.09 (m, 2H; Hb-7, H8), 3.11
(s, 6H; H13, H14), 3.32 (m, 2H; H15), 3.54 (td, J=10.7, J=4.2 Hz, 1H;
H6), 4.65 ppm (t, J=7.5 Hz, 2H; H12); 13C NMR (CDCl3): d=13.6
(C18), 15.9 (C9 or C10), 19.7 (C17), 21.1 (C1), 22.1 (C9 or C10), 22.8
(C4), 24.3 (C16), 25.9 (C8), 31.2 (C2), 34.0 (C3), 40.4 (C7), 47.8 (C13 and
C14), 48.1 (C5), 61.3 (C15), 81.8 (C6), 88.0 ppm (C12); elemental analysis
calcd (%) for C17H36NOClO4 (369.9): C 55.20, H 9.81, N 3.79; found: C
55.49, H 10.01, N 3.71.
Antielectrostatic properties: The antielectrostatic effect was measured on
a polyethylene film, which did not contain any lubricants or antioxidants.
Thin films of the studied salts were deposited on disks of diameter
0.125 m. The disks were stored for 24 h in an air-conditioned room at
208C with a relative humidity of 65%. The measuring apparatus and the
method have recently been described elsewhere.[37] The relative error in
the determination of two quantities did not exceed 5%.
X-ray crystallography: The crystal structure of butyldimethyl[(1R,2S,5R)-
(ꢀ)-menthoxymethyl]ammonium chloride (1e) was determined by single-
crystal X-ray diffraction at room temperature, using a Kuma KM-4 dif-
fractometer with a single-point detector and graphite-monochromated
CuKa radiation (l=1.54178 Š). The data were processed routinely and
the structure was solved by direct methods (Sheldrick, 1990)[38] and re-
fined with anisotropic thermal parameters by full-matrix least-squares
techniques (Sheldrick, 1997).[39] The H atoms were placed in calculated
Butyldimethyl[(1R,2S,5R)-(ꢀ)-menthoxymethyl]ammonium iodide (4):
1H NMR (CDCl3, 258C): d=0.82 (d, J=6.9 Hz, 3H; H9 or H10), 0.97
(m, 12H; Ha-3, H1, H9 or H10, Ha-7, Ha-4, H18), 1.40 (m, 4H; H2, H5,
H17), 1.70 (m, 4H; Hb-3, Hb-4, H16), 2.07 (m, 1H; H8), 2.22 (d, J=
11.5 Hz, 1H; Hb-7), 3.55 (s, 3H; H13 or H14), 3.36 (s, 3H; H13 or H14),
3.57 (m, 2H; H15), 3.65 (m, 1H; H6), 4.93, 5.03 ppm (d, J=6.87 Hz, 2H;
AB system); 13C NMR (CDCl3): d=13.4 (C18), 15.9 (C9 or C10), 19.4
4448
ꢀ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
Chem. Eur. J. 2005, 11, 4441– 4449

Chiral Ammonium-Based Ionic Liquids
FULL PAPER
positions. H atoms were placed in geometrically idealized positions. Only
the H atoms of water molecules were found in difference Fourier maps.
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bic, space group P212121, crystal size 0.5”0.3”0.1mm, a=7.5261(16), b=
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ATCC 25922, Proteus vulgaris NCTC 4635, Serratia marcescens
ATCC 8100; cocci: Staphylococcus epidermidis ATCC 49134, Staphylo-
coccus aures NCTC 4163, Micrococcus luteus NCTC 7743, Enterococcus
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Acknowledgements
This work was supported by the Polish Committee of Scientific Research
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Received: January 11, 2005
Published online: May 10, 2005
Chem. Eur. J. 2005, 11, 4441– 4449
www.chemeurj.org
ꢀ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4449