Densities, viscosities, and refractive indices of 1-hexyl-3-propanenitrile imidazolium ionic liquids incorporated with sulfonate-based anions

Article abstract of DOI:10.1021/je101316g

A new series of nitrile-functionalized room-temperature ionic liquids (RTILs), incorporating different anions, namely, dioctylsulfosuccinate, dodecylsulfate, benzenesulfonate, sulfobenzoate, and triflouromethanesulfonate, have been prepared and characteri

Full text of DOI:10.1021/je101316g

ARTICLE
pubs.acs.org/jced
Densities, Viscosities, and Refractive Indices of 1-Hexyl-3-
propanenitrile Imidazolium Ionic Liquids Incorporated with
Sulfonate-Based Anions
Abobakr K. Ziyada,† M. Azmi Bustam,† Cecilia D. Wilfred,‡ and Thanapalan Murugesan*,†
†Chemical Engineering Department and ‡Fundamental and Applied Sciences Department, Universiti Teknologi PETRONAS,
Tronoh-31750, Perak, Malaysia
S Supporting Information
b
ABSTRACT: A new series of nitrile-functionalized room-temperature ionic liquids (RTILs), incorporating different anions,
namely, dioctylsulfosuccinate, dodecylsulfate, benzenesulfonate, sulfobenzoate, and triflouromethanesulfonate, have been prepared
and characterized using FTIR-ATR, 1H NMR, and elemental analysis. Their physical properties such as density, viscosity, refractive
index, and thermal stability were measured and reported for a temperature range from (293.15 to 353.15) K at atmospheric pressure.
’ INTRODUCTION
In the recent years, ionic liquids (ILs) have attracted increas-
ing attention and intensive investigation and witnessed a steady
growth from the academics to industry due to their distinctive
properties.1,2 ILs are organic salts with organic cations and inorg-
anic or organic anions having melting points less than 100 °C and
negligible vapor pressure.3,4 They often exhibit many unique
advantages compared with conventional organic solvents, such as
wide temperature range of application, high thermal stability,
nonflammability, wide electrochemical window, high electrical
conductivity, and highly favorable solubility of molecules (polar
or nonpolar organic and inorganic compounds).5,6 These typical
properties of ILs open up possible applications as solvents for
reactions, absorption media for gas separation, heat transfer
fluids, separating agents in extractive and azeotropic distillation,
Figure 1. Structures of the cation and anions used in the present work.
biomass processing fluids, working fluids in a variety of electro-
chemical applications (batteries, capacitors, solar cells, etc.),
and studied the physiochemical properties of 1-alkylnitrile-3-
and also as lubricants.2,7,8 One of the most attractive features
methylimidazolium-based ILs incorporating chloride anions,18,19
of these ILs is that they can be easily prepared for any specific
but the physiochemical properties of 1-hexyl-3-propanenitrilei-
application either by careful selection of the cation or anion or
midazolium ILs incorporating anions such as dioctylsulfosucci-
both,9 or by attaching new functional groups, such as amine,
nate (DOSS), dodecylsulfate (DDS), benzenesulfonate (BS),
amide, nitrile,10 sulfonic acid, fluorous chains,11 ether, alcohol,12
sulfobenzoate (SBA), and triflouromethanesulfonate (TFMS)
carboxylic, and thiols,13 to the structure to impart the desired
have not been studied yet. In continuance of our previous studies
properties or reactivities.14 This ability results in an increasing
on the synthesis, characterization, and physicochemical proper-
number of applications.15 The ILs incorporated with functional
ties measurements of novel ILs,18-20 the present work is proposed
groups are called task-specific or functionalized ILs. These
to synthesize a series of new nitrile-functionalized ILs incorporating
relatively new type of ILs possess some distinctive features due
different anions (Figure 1) and to measure their physiochemical
to the presence of functional groups which are not present in the
properties. A series of 1-hexyl-3-propanenitrileimidazolium ILs
common ILs.16
(namely, 1-hexyl-3-propanenitrileimidazolium dioctysulfosuccinate
Knowledge and understanding of the properties of ILs is
[C2CNHim]DOSS, 1-hexyl-3-propanenitrileimidazolium dodecyl-
indispensable for choosing a suitable liquid for each envisaged
sulfate [C2CNHim]DDS, 1-hexyl-3-propanenitrileimidazolium ben-
application. The physical properties such as density and viscosity
zenesulfonate [C2CNHim]BS, 1-hexyl-3-propanenitrileimidazolium
are essential for the design of process equipment. Moreover,
complete data sets are required for the validation and improve-
ment of the property prediction methods, which can be applied
for molecular simulation as well as design and development of
the commercial process.17 Many researchers have synthesized
Received: December 15, 2010
Accepted: February 16, 2011
Published: March 07, 2011
r
2011 American Chemical Society
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Journal of Chemical & Engineering Data
ARTICLE
Table 1. Molecular Weight (mol wt.), Mass Fraction of Water (wH2O), Mass Fraction of Bromide (wBr), Start Temperatures (Ts),
and Decomposition Temperatures (Td)
[CNC2Him]DOSS
[CNC2Him]DDS
[CNC2Him]BS
[CNC2Him]SBA
[CNC2Him]TFMS
mol wt. (g mol-1
)
628.88
219
69
472.70
198
83
364.48
206
52
408.49
235
74
355.38
243
91
3
wH2O (106 w)
wBr (106 w)
Ts/K
536
566
498
528
544
581
541
575
493
521
Td/K
Table 2. Experimental Density, G, Values for [CNC2Him]-Based Ionic Liquids As a Function of Temperature
F/(g cm-3
)
3
T/K
[CNC2Him]DOSS
[CNC2Him]DDS
[CNC2Him]BS
[CNC2Him]SBA
[CNC2Him]TFMS
293.15
298.15
303.15
308.15
313.15
318.15
323.15
328.15
333.15
338.15
343.15
348.15
353.15
1.0927
1.0890
1.0854
1.0818
1.0783
1.0748
1.0713
1.0679
1.0644
1.0610
1.0576
1.0542
1.0507
1.1011
1.0978
1.0945
1.0912
1.0880
1.0847
1.0815
1.0783
1.0751
1.0719
1.0688
1.0656
1.0626
1.2260
1.2227
1.2194
1.2161
1.2128
1.2096
1.2063
1.2030
1.1997
1.1965
1.1933
1.1901
1.1878
1.2481
1.2446
1.2412
1.2380
1.2347
1.2315
1.2282
1.2250
1.2218
1.2186
1.2154
1.2121
1.2089
1.2896
1.2857
1.2819
1.2783
1.2746
1.2710
1.2674
1.2638
1.2602
1.2566
1.2531
1.2492
1.2458
sulfobenzoate [C2CNHim]SBA, and 1-hexyl-3-propanenitrileimida-
zolium triflouromethanesulfonate [C2CNHim]TFMS) were syn-
thesized, and their densities and dynamic viscosities were measured
at atmospheric pressure within a temperatures range of (293.15 to
353.15) K while their refractive indices were measured at a tempera-
tures range of (293.15 to 333.15) K. The thermal expansion
coefficients of the present ILs were calculated from the measured
density as a function of temperature.
was washed with ethyl acetate, and the purification was accomplished
using the standard procedure.20
1-Hexyl-3-propanenitrile imidazolium dioctylsulfosuccinate
[C2CNHim]DOSS was synthesized by mixing [C2CNHim]Br
(0.03 mol) and sodium dioctylsulfosuccinate (0.03 mol) in
50 mL of acetone. The mixture was stirred at room temperature
(25 °C) for 48 h, and then the solid precipitate was separated,
and the solvent was removed under vacuum. The resulting pale
yellow viscous compound was cooled to room temperature and
washed with ethyl acetate and diethyl ether, and the remaining
solvent was removed under vacuum at 80 °C for 48 h.
’ EXPERIMENTAL SECTION
For the synthesis of 1-hexyl-3-propanenitrileimidazolium do-
decylsulfate [C2CNHim]DDS, [C2CNHim]Br (0.04 mol) and
sodium dodecylsulfate C12H25OSO3Na (0.04 mol) were mixed
in 40 mL of deionized water (60 °C). The mixture was stirred at
room temperature for 48 h. The excess water was slowly removed
under vacuum at 80 °C, and then 50 mL of CH2Cl2 was added to
the precipitate and then filtered. The viscous extract was repeti-
tively washed with deionized water until it was bromide-free. The
remaining solvent was removed under vacuum at 80 °C for 48 h.
Instead of sodium dodecylsulfate (0.04 mol), sodium benze-
nesulfonate (0.04 mol), sodium 3-sulfobenzoate (0.04 mol),
and sodium triflouromethanesulfonate (0.04 mol) were used to
synthesize 1-hexyl-3-propanenitrileimidazolium benzenesulfonate
[C2CNHim]BS, 1-hexyl-3-propanenitrileimidazolium sulfobenzoate
[C2CNHim]SBA, and 1-hexyl-3-propanenitrileimidazolium triflour-
omethanesulfonate [C2CNHim]TFMS, respectively, and a similar
procedure was adopted.
Materials. The ILs used in the present study were synthesized
using chemicals of analytical grade. The CAS number, source,
and grades of the chemicals used are as follows: imidazole (288-
32-4, Aldrich 99 %), acetone (67-64-1, Sigma-Aldrich 99.8 %),
acrylonitrile (107-13-1, Aldrich 99 %), anhydrous methanol (67-
56-1, Sigma-Aldrich 99.8 %), 1-bromohexane (111-15-1, Aldrich
99 %), anhydrous ethylacetate (141-78-6, Sigma-Aldrich 99.8 %),
sodium dioctylsulfosuccinate (209-406-4, Aldrich 98 %), sodium
dodecylsulfate (205-788-1, Sigma-Aldrich 99 %), sodium benze-
nesulfonate (515-42-4, Aldrich 97 %), sodium 3-sulfobenzoate
(17625-03-5, Aldrich 97 %), sodium triflouromethanesulfonate
(2926-30-9, Aldrich 98 %), and diethyl ether (60-29-7, Sigma-
Aldrich 99 %). All the chemicals were used without further
purification.
Synthesis of Ionic Liquids. The syntheses of the ILs used in
the present study were based on a metathesis reaction of 1-hexyl-
3-propanenitrile imidazolium bromide ([C2CNHim]Br) and
alkali metal salts with different anions. [C2CNHim]Br was synthe-
sized by direct reaction of imidazole with acrylonitrile in methanol,
and the product was then reacted with 1-bromohexane. The product
Characterization and Properties Measurements. The in-
struments used for the measurements of the physical properties
of the present synthesized ILs were calibrated using ultrapure
Millipore quality water and validated with ILs of established
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ARTICLE
Table 3. Experimental Viscosity, η, Values for [CNC2Him]-Based Ionic Liquids As a Function of Temperature
η/(mPa s)
3
T/K
[CNC2Him]DOSS
[CNC2Him]DDS
[CNC2Him]BS
[CNC2Him]SBA
[CNC2Him]TFMS
293.15
298.15
303.15
308.15
313.15
318.15
323.15
328.15
333.15
338.15
343.15
348.15
353.15
--
19896.3
12117.4
7571.4
4586.7
2939.5
1947.7
1264.7
848.3
--
13769.7
8252.7
5185.2
3354.6
2051.0
1301.8
846.3
7079.4
4268.1
2865.6
1795.1
1170.4
781.3
537.6
359.9
274.2
181.0
133.6
94.6
19212.0
11463.0
7578.3
4765.8
3001.1
1953.3
1189.9
830.5
2243.6
1469.7
991.9
648.5
437.8
301.9
214.0
155.1
102.7
77.4
566.9
557.3
579.4
390.1
352.1
411.4
274.9
225.5
54.8
278.6
189.5
133.6
40.1
191.2
133.6
70.0
92.8
29.4
Table 4. Experimental Refractive Index, nD, Values for [CNC2Him]-Based Ionic Liquids As a Function of Temperature
nD
T/K
[CNC2Him]DOSS
[CNC2Him]DDS
[CNC2Him]BS
[CNC2Him]SBA
[CNC2Him]TFMS
298.15
303.15
308.15
313.15
318.15
323.15
328.15
333.15
1.47970
1.47841
1.47709
1.47580
1.47447
1.47305
1.47171
1.47029
1.48409
1.48269
1.48125
1.47991
1.47863
1.47702
1.47566
1.47422
1.52700
1.52610
1.52499
1.52382
1.52266
1.52145
1.52025
1.51899
1.52295
1.52221
1.52146
1.52029
1.51936
1.51800
1.51666
1.51502
1.52975
1.52891
1.52774
1.52683
1.52590
1.52464
1.52334
1.52226
properties. The data established by our research group for the ILs
1-butyl-3-propanenitrileimidazolium bromide [C2CNBim]Br,
1-butyl-
pyridinium bis(trifluoromethylsulfonyl) imide [C4py][Tf2N]n
and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)-
imide [C6Mim]Tf2N were used for the validation of the repro-
ducibility of the instruments.20-22
(150 ꢀ 4.0) mm analytical column (Metrosep A Supp 5-150)
and (5.0 ꢀ 4.0) mm guard column (Metrosep A Supp 4/5).21
The measurements were analyzed using Metrodata IC Net 2.3
software.
Thermogravimetry Measurements. The start and onset
temperatures of the present synthesized ILs were determined
using Perkin-Elmer, Pyris V-3.81. The samples were placed in
aluminum pans under nitrogen atmosphere at a heating rate of
FTIR-ATR, NMR, and Elemental Analysis. The present
synthesized ILs were characterized using Fourier transformation
infrared (FTIR) spectra. The spectra were recorded in a Shimadzu
FTIR-8400S Fourier Transform Infrared Spectrometer (FTIR)
in the mid region [(4000 to 400) cm-1] using the Attenuated
Total Reflectance (MIRacle ATR) measurement mode. A CHNS-
932 (LECO instruments) elemental analyzer was used to determine
the individual percentage of elements. A Bruker Avance 300
10 °C min-1. The estimated water and bromide content, the
3
start temperature (Ts), and the decomposition temperature (Td)
are presented in Table 1.
Densities and Viscosities Measurements. Density and
viscosity of all ionic liquids were measured in a temperature
range (293.15 to 353.15) K at atmospheric pressure using a
Stabinger viscometer (Anton-Paar model SVM3000).20,21 The
temperature was controlled to within ( 0.01 °C. The repeat-
ability of measurements were ( 5 10-4 g cm-3 and 0.75 % for
1
spectrophotometer was used to determine the H NMR spectra
of the present ILs. The estimated purities of the present synthesized
ionic liquids, namely, [CNC2Him]DOSS; [CNC2Him]DDS;
[CNC2Him]BS; [CNC2Him]SBA, and [CNC2Him]TFMS, are
96.8 %, 97.0 %, 97.2 %, 96.7 %, and 96.4 %, respectively.
Water and Bromide Content. A coulometric Karl Fischer
titrator (DL 39 Mettler Toledo) with CombiCoulomat fritless
Karl Fischer reagent (Merck)20,21 was used to determine the water
content of the ILs. The measurement for each IL was made in
triplicate, and the average values are reported.
3
3
density and viscosity, respectively.20,21 The standard calibration
fluid provided by the supplier was used for the calibration of the
viscometer followed by the validation of the measurements using
ionic liquids with known densities and viscosities.20,22 The
measured densities and viscosities are presented in Table 2 and
Table 3, respectively.
Refractive Indices Measurements. An ATAGO program-
mable digital refractometer (RX-5000 alpha) with a measuring
Bromide content measurements were conducted by ion
chromatography (Metrohm model 761 Compact IC) with
accuracy of ( 4 10-5 was used to measure the refractive index of
3
various ILs in a temperature range of (298.15 to 333.15) K. The
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Table 5. Fitting Parameters of Equation 1 for the Density of
the ILs
[CNC2Him]DDS: 1H NMR 300 MHz, D2O; δ 0.87 (t, 6H),
1.30 (br, 20H), 1.81 (br, 4H), 1.93 (m, 2H), 3.18 (t, 2H), 4.19 (t,
2H), 4.63 (m, 2H), 7.51 (t, 2H), 7.75 (t, 2H), 9.20 (s, 2H), 9.92
(s, 1H).
Ionic liquid
A0
A1 104
SD 104
3
3
Analysis (% calculated): C 61.09 (60.98), H 9.92 (9.81), N
8.81 (8.89), S 6.73 (6.78).
[CNC2Him]DOSS
[CNC2Him]DDS
[CNC2Him]BS
1.296715
1.289327
1.415283
1.438327
1.502418
-6.97
-6.43
-6.46
-6.50
-7.27
1.44
1.46
2.87
1.14
1.30
1
[CNC2Him]BS: H NMR 300 MHz, D2O; δ 0.81 (t, 3H),
1.26 (m, 6H), 1.84 (m, 2H), 3.15 (t, 2H), 4.19 (t, 2H), 4.56 (t,
2H), 7.50 (d, 3H), 7.57 (s, 1H), 7.61 (s, 1H), 7.75 (s, 1H), 8.96
(d, 2H).
[CNC2Him]SBA
[CNC2Him]TFMS
Analysis (% calculated): C 51.35 (59.31), H 7.14 (7.19), N
11.57 (11.53), S 8.72 (8.80).
Table 6. Fitting Parameters of Equation 2 for the Refractive
Index of the ILs
[CNC2Him]SBA: 1H NMR 300 MHz, D2O; δ 0.77 (t, 3H),
1.21 (m, 6H), 1.80, (m, 2H), 3.13 (t, 2H), 4.16 (t, 2H), 4.53 (t,
2H), 7.53 (s, 1H), 7.59 (s, 1H), 7.96 (d, 2H), 8.06 (s, 1H), 8.27
(d, 2H), 9.93 (s, 1H).
ionic liquid
A2
A3 104
SD 104
3
3
[CNC2Him]DOSS
[CNC2Him]DDS
[CNC2Him]BS
1.559855
1.568024
1.596133
1.590568
1.594194
-2.69
-2.81
-2.31
-2.25
-2.16
1.30
1.55
1.19
3.34
2.16
Analysis (% calculated): C 55.93 (55.86), H 6.45 (6.42), N
10.35 (10.29), S 7.89 (7.85).
[CNC2Him]TFMS: 1H NMR 300 MHz, D2O; δ 0.81 (t, 3H),
1.26 (m, 2H), 1.84 (m, 6H), 3.14 (t, 2H), 4.21 (t, 2H), 4.55 (t,
2H), 7.56 (s, 1H), 7.60 (s, 1H), 7.92 (s, 1H).
[CNC2Him]SBA
[CNC2Him]TFMS
Analysis (% calculated): C 43.98 (43.94), H 5.78 (5.67), N
11.70 (11.82), S 9.13 (9.02).
Table 7. Fitting Parameters of Equation 3 for the Viscosity of
the ILs
The thermal stability of the present ILs is reported as the start
and decomposition temperatures. The decomposition tempera-
ture depends on alkyl chain of the cation and mainly on the type
of the anion.21 The thermogravimetric results show that the
present ILs exhibited short-term thermal stability up to 536 K at a
ionic liquid
A4
A5 10-3
SD 102
3
3
[CNC2Him]DOSS
[CNC2Him]DDS
[CNC2Him]BS
-8.60621
-8.83420
-7.93228
-9.22432
-7.72063
3.84509
3.86561
3.44860
3.97177
3.24659
0.83
1.11
1.32
3.47
0.75
scan rate of 10 °C min-1, except for [CNC2Him]DDS and
3
[CNC2Him]TFMS up to (498 and 493) K, respectively (Table 1).
The density of the ILs (Table 2) shows a linear decrease with
increasing temperature. It was found that the densities of the
present ILs are higher when paired with the trifluoromethane-
sulfonate anion followed by sulfobenzoic acid, bezenesulfonate,
and then by dodecylsulfate anion. The lowest densities were
observed with the dioctylsulfosuccinate anion. These results
showed that an increase in the anion molecular weight does
not directly correspond to the rise in the density values for
the present ILs, and a similar behavior for other imidazolium-based
ILs was observed by Saꢀnchez et al.17and Gardaset al.23 The
measured densities of the present ILs incorporating the anions
DOSS, DDS, BS, SBA, and TFMS at 298.15 K are (1.0890, 1.0978,
[CNC2Him]SBA
[CNC2Him]TFMS
temperature was controlled with an accuracy of ( 0.05 °C. The
apparatus was calibrated and checked before each series of
measurements using pure organic solvents (methanol, ethyl-
acetate) with known refractive indices.20,21 Dried samples (water
contents are given in Table 1) kept in desiccators were directly
placed into the measuring cell, and the measurements were made
in triplicate. The average values are reported in Table 4.
1.2227, 1.2446, and 1.2857) g cm-3, respectively. The present ILs
’ RESULTS AND DISCUSSIONS
3
Figure 1 shows the structure of the cation and anions used.
The FTIR spectra (Figure 1 in Supporting Information) of the
present ILs show the characteristic absorption bands of the nitrile
group in the range (2248 to 2256) cm-1 for CdN at (1560 to
1665) cm-1 and exhibit C-H bond at (3080 to 3145) cm-1, and
showed lower densities compared to other nitrile-functionalized
ILs reported by Zhang et al.19 (the densities of [C3CNMim]BF4
and [C3CNMim]NTf2 are (1.319 and 1.519) g cm-3) and Zhao
3
et al.18 (the densities of [C2CNMim]BF4, [C3CNMim]BF4, and
[C4CNMim]Cl are (2.15, 1.87, and 1.61) g cm-3, respectively).
3
a weaker C-H bonds stretches from (2854 to 2933) cm-1
,
The lower density of these ILs might be due to the presence of a
long alkyl chain compared to the other nitrile-functionalized ILs.20
The measured viscosities are higher for the IL with DOSS anion,
while it was the lowest for the IL with TFMS anion. The viscosities
of [CNC2Him]DOSS and [CNC2Him]TFMS at 298.15 K are
which are similar to that reported for other nitrile-functionalized
ILs.18-20 In addition, these ILs show a S-O stretching band in the
range (1181 to 1195) cm-1 and the strong peak at 1730 cm-1 for the
[CNC2Him]DOSS, which is due to the presence of the CdO group
in the dioctylsulfosuccinate anion.
(19896.3 and 4268.1) mPa s, respectively. As can be observed, a
3
1
The results of H NMR and elemental analysis of the ionic
rise in temperature caused a significant reduction in the viscosities of
the present synthesized ILs. However, as can be seen in Table 3, the
viscosity values of the ILs show functional group and alkyl chain
length dependency.24 An addition of functional group or increasing
alkyl chain length has been found to give higher viscosity values. The
viscosity values of the present ionic liquids are much higher
compared with the reported similar nitrile-functionalized ILs. For
[C2CNMIm]BF4, [C3CN\MIm]BF4, and [C4CN\MIm]Cl the
liquids are as follows:
[CNC2Him]DOSS: 1H NMR 300 MHz, D2O; δ 0.88
(t, 15H), 1.28 (br, 20H), 1.59 (m, 4H), 1.92 (m, 2H), 2.30
(m, 4H), 3.17 (m, 2H), 4.01 (t, 2H), 4.16 (t, 2H), 4.25 (t, 2H),
4.71 (m, 1H), 7.30 (s, 1H), 7.80 (s, 1H), 9.63 (s, 1H).
Analysis (% calculated): C 61.03 (61.12), H 9.41 (9.30), N
6.52 (6.68), S 5.13 (5.10).
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Table 8. Thermal Expansion Coefficients rp for [CNC2Him]-Based Ionic Liquids
Rp 104/(K-1
)
3
T/K
[CNC2Him]DOSS
[CNC2Him]DDS
[CNC2Him]BS
[CNC2Him]SBA
[CNC2Him]TFMS
293.15
298.15
303.15
308.15
313.15
318.15
323.15
328.15
333.15
338.15
343.15
348.15
353.15
6.41
6.43
6.45
6.48
6.50
6.52
6.54
6.56
6.58
6.60
6.63
6.65
6.67
5.67
5.68
5.70
5.71
5.73
5.75
5.76
5.78
5.80
5.81
5.83
5.85
5.87
5.21
5.22
5.24
5.25
5.26
5.28
5.29
5.31
5.32
5.33
5.35
5.36
5.38
5.31
5.32
5.34
5.35
5.36
5.38
5.39
5.41
5.42
5.44
5.45
5.47
5.48
5.81
5.83
5.84
5.86
5.88
5.89
5.91
5.93
5.95
5.97
5.98
6.00
6.02
viscosities are (65.5, 352, and 5222) mPa s, respectively.18,19
densities of the present ILs decrease linearly with temperature,
the coefficients of volume expansion at constant pressure were
easily obtained from linear fits of the density data using the
following equation20,21
3
Furthermore, the present ILs except [C2CNHim]DOSS show lower
viscosities than the similar ILs with bromide anion (for [C2CN
Him]Br at 303.15 K is 15893.0 mPa s).20
3
The measured data of the refractive indices of the
ILs [C2CNHim]DOSS, [C2CNHim]DDS, [C2CNHim]BS,
[C2CNHim]SBA, and [C2CNHimM]TFMS are presented in
Table 4. The refractive index values of the present ionic liquids
are in good agreement with that reported by Zhang et al.19 for
other nitrile-functionalized ILs; for [C3CNMIm]N(CN)2,
[C3CNMMIm]N(CN)2, and [C3CNPy]N(CN)2, the refractive
indices are 1.5258, 1.5255, and 1.5453, respectively. Moreover,
the present ILs show similar refractive index values as compared
with similar nitrile ILs incorporating the bromide anion.20 As can
be seen in Table 4, the functional group and alkyl chain length
attached to the anion have a large effect on the refractive index values,
and also the refractive indices decrease linearly with increasing temp-
erature.
Rp=ðK-1
Þ
¼
¼
-ð1=FÞ ðDF=DTÞp
3
ð5Þ
-ðA1ÞðA0 þ A1TÞ
where Rp is the thermal expansion coefficient in K-1. A0 and A1
are the fitting parameters of eq 1. The variation of the volumetric
expansion with temperature shows that ILs have less expansion
capacity than regular organic solvents.24 The thermal expansion
coefficients of the present ILs vary between (5.21 10-4 and
3
6.67 10-4) K-1, which is lower than that for traditional organic
3
solvents. The calculated expansivities are similar to those re-
ported for [C2CNBim]Br, [C2CNHim]Br, [C2CNOim]Br, and
[C2CNDim]Br, which are in the range of (5.09 to 6.36) 10-4
3
K-1 20
.
Similar ranges of thermal expansion coefficients have
The measured densities, viscosities, and refractive indices were
correlated as a function of temperature T using the following
form of equations20,25
been earlier reported for the imidazolium-, pyridinium-, phos-
phonium-, and ammonium-based ILs, (5.0 to 6.5) 10-4 K-1 25
.
3
As can be seen in Table 8, the thermal expansion coefficients of
this series of ILs increases with increasing alkyl chain length of
the anion with the exception of the TFMS anion.
F=ðg cm-1Þ ¼ A0 þ A1T
ð1Þ
ð2Þ
ð3Þ
3
nD ¼ A2 þ A3T
’ CONCLUSION
log η=ðmPa sÞ ¼ A4 þ A5=T
A series of new nitrile-functionalized ILs incorporating differ-
ent anions were synthesized, and their properties, namely,
density, dynamic viscosity, and refractive index, were measured.
Furthermore thermogravimetry measurements show that the
present ILs feature higher thermal stability than their pure
counterparts incorporating bromide anion. Density and refrac-
tive index show linear behavior with temperature. Empirical
correlations (eqs 1, 2, and 3) were proposed to represent the
present experimental results. Finally, these ILs show weak
temperature dependency for the thermal expansion coefficient.
3
The coefficients A0, A1, A2, A3, A4, and A5 are estimated using the
method of least-squares and are listed in Tables 5, 6, and 7,
respectively, together with the standard deviations (SD) calcu-
lated as follows20,21
vffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
u
nDAT
u
2
u ∑ ðZexp - ZcalÞ
t
j
SD ¼
ð4Þ
nDAT
where zexp and zcal. are the experimental and calculated values
(using eqs 1, 2, and 3), respectively, and nDAT is the number of
experimental points.
’ ASSOCIATED CONTENT
S
Supporting Information. Additional figure. This materi-
al is available free of charge via the Internet at http://pubs.acs.
org.
b
The changes in the liquid volume with temperature were
evaluated using the thermal expansion coefficient. Since the
2347
dx.doi.org/10.1021/je101316g |J. Chem. Eng. Data 2011, 56, 2343–2348

Journal of Chemical & Engineering Data
ARTICLE
’ AUTHOR INFORMATION
(19) Zhang, Q.; Li, Z.; Zhang, J.; Zhang, S.; Zhu, L.; Yang, J.; Zhang,
X.; Deng, Y. Physicochemical Properties of Nitrile-Functionalized Ionic
Liquids. J. Phys. Chem. B 2007, 111, 2864–2872.
(20) Ziyada, A. K.; Wilfred, C. D.; Bustam, M. A.; Man, Z.;
Murugesan, T. Thermophysical Properties of 1-Propyronitrile-3-alkyli-
midazolium Bromide Ionic Liquids at Temperatures from (293.15 to
353.15) K. J. Chem. Eng. Data 2010, 55, 3886–3890.
(21) Yunus, N. M.; Mutalib, M. I. A.; Man, Z.; Bustam, M. A.;
Murugesan, T. Thermophysical properties of 1-alkylpyridinum bis-
(trifluoromethylsulfonyl)imide ionic liquids. J. Chem. Thermodyn.
2010, 42, 491–495.
(22) Muhammad, A.; Mutalib, M. I. A.; Wilfred, C. D.; Murugesan,
T.; Shafeeq, A. Thermophysical properties of 1-hexyl-3-methyl imida-
zolium based ionic liquids with tetrafluoroborate, hexafluorophosphate
and bis(trifluoromethylsulfonyl)imide anions. J. Chem. Thermodyn.
2008, 40, 1433–1438.
(23) Gardas, R. L.; Freire, M. G.; Carvalho, P. J.; Marrucho, I. M.;
Fonseca, I. M. A.; Ferreira, A. G. M.; Coutinho, J. A. P. High-pressure
densities and derived thermodynamic properties of imidazolium-based
ionic liquids. J. Chem. Eng. Data 2007, 52 (1), 80–88.
(24) Hasse, B.; Lehmann, J.; Assenbaum, D.; Wasserscheid, P.;
Leipertz, A.; Fro ba, A. P. Viscosity, Interfacial Tension, Density,
and Refractive Index of Ionic Liquids [EMIM][MeSO3],[EMIM]
[MeOHPO2],[EMIM][OcSO4], and [BBIM][NTf2] in Depen-
dence on Temperature at Atmospheric Pressure. J. Chem. Eng. Data
2009, 54 (9), 2576–2583.
Corresponding Author
*E mail:murugesan@petronas.com.my;tmgesan_57@yahoo.com.
’ REFERENCES
(1) Pereiro, A. B.; Veiga, H. I. M.; Esperanc-a, J.; Rodríguez, A. Effect
of temperature on the physical properties of two ionic liquids. J. Chem.
Thermodyn. 2009, 41 (12), 1419–1423.
(2) Saha, S.; Hamaguchi, H. Effect of water on the molecular
structure and arrangement of nitrile-functionalized ionic liquids. J. Phys.
Chem. B 2006, 110 (6), 2777–2781.
(3) Earle, M. J.; Seddon, K. R. Ionic liquids. Green solvents for the
future. Pure Appl. Chem. 2000, 72, 1391–1398.
(4) Newington, I.; Perez-Arlandis, J. M.; Welton, T. Ionic liquids as
Designer Solvents for Nucleophilic Aromatic Substitutions. Org. Lett.
2007, 9, 5247–5250.
(5) Freire, M. G.; Carvalho, P. J.; Fernandes, A. M.; Marrucho, I. M.;
Queimada, A. J.; Coutinho, J. A. P. Surface tensions of imidazolium
based ionic liquids: Anion, cation, temperature and water effect.
J. Colloid Interface Sci. 2007, 314, 621–630.
(6) Chiappe, C.; Pieraccini, D. Kinetic Study of the Addition of
Trihalides to Unsaturated Compounds in Ionic Liquids. Evidence of a
Remarkable Solvent Effect in the Reaction of ICl2-. J. Org. Chem. 2004,
69, 6059–6064.
(7) Vila, J.; Ginꢀes, P.; Pico, J. M.; Franjo, C.; Jimꢀenez, E.; Varela,
L. M.; Cabeza, O. Temperature dependence of the electrical conductiv-
ity in EMIM based ionic liquids. Evidence of Vogel-Tamman-F€ulcher
behavior. Fluid Phase Equilib. 2006, 242, 141–146.
(25) Gu, Z.; Brennecke, J. F. Volume expansivities and isothermal
compressibilities of imidazolium and pyridinium-based ionic liquids.
J. Chem. Eng. Data 2002, 47 (2), 339–345.
(8) Ye, C.; Liu, W.; Chen, Y.; Yu, L. Room-temperature ionic liquids:
a novel versatile lubricant. Chem. Commun. 2001, 21, 2244–2245.
(9) Torrecilla, J. S.; Palomar, J.; Garcí, J. n.; Rodríguez, F. Effect of
Cationic and Anionic Chain Lengths on Volumetric, Transport, and
Surface Properties of 1-Alkyl-3-methylimidazolium Alkylsulfate Ionic
Liquids at (298.15 and 313.15) K. J. Chem. Eng. Data 2009, 54, 1297–1301.
(10) Zhang, S.; Chen, Y.; Li, F.; Lu, X.; Dai, W.; Mori, R. Fixation and
conversion of CO2 using ionic liquids. Catal. Today 2006, 115, 61–69.
(11) Liu, X.-M.; Song, Z.-X.; Wang, H.-J. Density Functional Theory
Study on the -SO3H Functionalized Acidic Ionic Liquids. Struct. Chem.
2009, 20, 509–515.
(12) Fei, Z.; Ang, W. H.; Zhao, D.; Scopelliti, R.; Zvereva, E. E.;
Katsyuba, S. A.; Dyson, P. J. Revisiting Ether-Derivatized Imidazolium-
Based Ionic Liquids. J. Phys. Chem. B 2007, 111, 10095–10108.
(13) Nockemann, P.; Thijs, B.; Parac-Vogt, T. N.; Hecke, K. V.;
Meervel,t, L. V.; Tinant, B.; Hartenbach, I.; Schleid, T.; Ngan, V. T.;
Nguyen, M. T.; Binnemans, K. Carboxyl-Functionalized Task-Specific
Ionic Liquids for Solubilizing Metal Oxides. Inorg. Chem. 2008,
47, 9987–9999.
(14) Davis, J. H. Task-Specific Ionic Liquids. Chem. Lett. 2004,
33, 1072–1077.
(15) Mazille, F.; Fei, Z.; Kuang, D.; Zhao, D.; Zakeeruddin, S. M.;
Gr€atzel, M.; Dyson, P. J. Influence of Ionic Liquids Bearing Functional
Groups in Dye-Sensitized Solar Cells. Inorg. Chem. 2006,
45, 1585–1590.
(16) Fei, Z.; Zhao, D.; Pieraccini, D.; Ang, W. H.; Geldbach, T. J.;
Scopelliti, R.; Chiappe, C.; Dyson, P. J. Development of Nitrile-
Functionalized Ionic Liquids for C- C Coupling Reactions: Implication
of Carbene and Nanoparticle Catalysts. Organometallics 2007, 26 (7),
1588–1598.
(17) Sanchez, L. G.; Espel, J. R.; Onink, F.; Meindersma, G. W.;
Haan, A. B. Density, viscosity, and surface tension of synthesis grade
imidazolium, pyridinium, and pyrrolidinium based room temperature
ionic liquids. J. Chem. Eng. Data 2009, 54 (10), 2803–2812.
(18) Zhao, D.; Fei, Z.; Scopelliti, R.; Dyson, P. J. Synthesis and
Characterization of Ionic Liquids Incorporating the Nitrile Function-
ality. Inorg. Chem. 2004, 43, 2197–2205.
2348
dx.doi.org/10.1021/je101316g |J. Chem. Eng. Data 2011, 56, 2343–2348