This document summarizes research determining ion-specific equation coefficients for the Abraham solvation parameter model for several ionic liquid solvents. The researchers compiled partition coefficient data for solutes dissolved in five ionic liquids and correlated the data using the Abraham model. They were able to describe the partition coefficients within 0.13 log units. Cation-specific coefficients were then calculated for each ionic liquid, allowing predictions of solute partitioning in 76 ionic liquid solvents using previously reported anion coefficients.

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Physics and Chemistry of Liquids
An International Journal
ISSN: 0031-9104 (Print) 1029-0451 (Online) Journal homepage: http://www.tandfonline.com/loi/gpch20
Ion-specific equation coefficient version
of the Abraham model for ionic liquid
solvents: determination of coefficients
for tributylethylphosphonium, 1-butyl-1-
methylmorpholinium, 1-allyl-3-methylimidazolium
and octyltriethylammonium cations
Bihan Jiang, Melissa Y. Horton, William E. Acree Jr. & Michael H. Abraham
To cite this article: Bihan Jiang, Melissa Y. Horton, William E. Acree Jr. & Michael H. Abraham
(2016): Ion-specific equation coefficient version of the Abraham model for ionic liquid solvents:
determination of coefficients for tributylethylphosphonium, 1-butyl-1-methylmorpholinium,
1-allyl-3-methylimidazolium and octyltriethylammonium cations, Physics and Chemistry of
Liquids, DOI: 10.1080/00319104.2016.1218009
To link to this article: http://dx.doi.org/10.1080/00319104.2016.1218009
Published online: 08 Aug 2016. Submit your article to this journal
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2. Ion-specific equation coefficient version of the Abraham model
for ionic liquid solvents: determination of coefficients for
tributylethylphosphonium, 1-butyl-1-methylmorpholinium,
1-allyl-3-methylimidazolium and octyltriethylammonium cations
Bihan Jianga
, Melissa Y. Hortona
, William E. Acree Jr.a
and Michael H. Abrahamb
a
Department of Chemistry, University of North Texas, Denton, TX, USA; b
Department of Chemistry, University
College London, London, UK
ABSTRACT
Gas-to-ionic liquid partition coefficient data have been assembled from
the published chemical literature for solutes dissolved in 1-allyl-3-methy-
limidazolium dicyanamide, 1-allyl-3-methylimidazolium bis(trifluoro-
methylsulphonyl)imide, octyltriethylammonium bis(trifluomethyl-
sulphonyl)imide, tributylethylphosphonium diethylphosphate and 1-
butyl-1-methylmorpholinium tricyanomethanide. The published experi-
mental data were converted to water-to-ionic liquid partition coefficients
using standard thermodynamic relationships. Both sets of partition coeffi-
cients were correlated with the Abraham solvation parameter model. The
derived Abraham model correlations described the observed partition
coefficient data to within 0.13 log units. Cation-specific equation coeffi-
cients were calculated for each of the cations present in the five ionic
liquid solvents studied. The calculated cation-specific equation coefficients
can be combined with previously reported ion-specific equation coeffi-
cients for 19 different anions to yield Abraham model correlations for
predicting the partitioning the behaviour of solutes in 76 different anhy-
drous ionic liquid solvents.
ARTICLE HISTORY
Received 30 June 2016
Accepted 25 July 2016
KEYWORDS
Ionic liquid solvents;
partition coefficients; solute
transfer processes; Abraham
model correlations
1. Introduction
Ionic liquid (IL) solvents have been successfully employed in separation processes involving the
removal of nitrogen and sulphur heteroatom compounds from crude petroleum products,[1–6]
efficient removal of carbon dioxide from other light inorganic gas (nitrogen and oxygen) and
combustion organic gas (methane, ethane, ethene, acetylene) samples,[7–11] and removal of acidic
gases (sulphur dioxide and carbon dioxide) from post-combustion flue gas effluents.[12–18]
Considerable effort has been expended in experimentally determining the capacity that IL solvents
have towards absorbing various organic compounds and separation factors that IL solvents exhibit
for performing various practical chemical separations. Selectivity factors have been measured and
compiled for alkane vs. alkene (hexane/1-hexene,[19,20] cyclohexane/cyclohexene [20]), alkane vs.
benzene (hexane/benzene [20,21]) and alkane vs. heteroatom aromatic hydrocarbon (cyclohexane/
pyridine,[22] cyclohexane/thiophene,[22] hexane/pyridine,[21] hexane/thiophene [21]) separations
based on experimentally determined infinite dilution activity coefficients, γ1
solute, for the respective
solutes dissolved in the IL solvents. While the observed thermodynamic data provide valuable
information regarding whether the desired chemical separation can be achieved using the IL
CONTACT William E. Acree, Jr. acree@unt.edu
© 2016 Informa UK Limited, trading as Taylor & Francis Group
PHYSICS AND CHEMISTRY OF LIQUIDS, 2016
http://dx.doi.org/10.1080/00319104.2016.1218009

3. solvents studied, it is not practical to perform measurements for every organic solute pair dissolved
in every IL solvent. It is estimated that the number of possible IL solvents may exceed 1014
[23]
when one considers all of the different cation–anion pair combinations.
To facilitate the use of ILs in industrial processes involving separations, researchers have
turned to predictive methods to generate activity coefficients of solutes dissolved in IL solvents,
as well as to estimate other physical properties of IL solvents that may be needed in process design
computations. Predictive methods have involved both theoretical and semi-theoretical treatments,
as well as approaches based on group contribution and molecular fragment schemes, linear free
energy relationships (LFERs) and quantitative structure–property relationships (QSPRs). Group
contribution methods have been proposed, which enable one to predict infinite dilution activity
coefficients and gas–to-liquid partition coefficients of solutes dissolved in ILs,[24–26] to predict
enthalpies of solvation of organic solutes dissolved in ILs,[27] and to estimate viscosities,[28,29]
thermal conductivities,[30,31] isobaric heat capacities,[32–34] surface tensions [35] and densities
[36] of ILs at both 298 K and as a function of temperature. In several of the above methods the
entire cation was defined as one functional group and the entire counter-anion was defined as a
second functional group.
Our contribution towards facilitating the use of IL solvents in chemical separation processes
has been to develop mathematical correlations based on the Abraham model that enable one to
predict infinite dilution activity coefficients and chemical separation factors. The Abraham model
[37] is an LFER approach that can describe solute transfer between two condensed phases:
log P ¼ cp;il þ ep;ilÁE þ sp;ilÁS þ ap;ilÁA þ bp;ilÁB þ vp;ilÁV (1)
or solute transfer to a condensed phase from the vapour phase:
log K ¼ ck;il þ ek;ilÁE þ sk;ilÁS þ ak;ilÁA þ bk;ilÁB þ lk;ilÁL (2)
In the present study one of the condensed phases is the IL solvent. Equation (1) will thus describe
the water-to-IL solvent partition coefficient, log P, while Equation (2) will describe the gas-to-IL
partition coefficient, log K. Uppercase alphabetic letters on the right-hand side of Equations (1)
and (2) represent the properties of the dissolved solute and are called solute descriptors, which are
unique to a given solute molecule. Solute descriptors are defined as follows: the solute excess
molar refractivity in units of (cm3
mol–1
)/10 (E), the solute dipolarity/polarisability (S), the overall
or summation hydrogen-bond acidity and basicity (A and B, respectively), the McGowan volume
in units of (cm3
mol–1
)/100 (V), and the logarithm of the gas-to-hexadecane partition coefficient
at 298 K (L). Once calculated, the solute descriptors can be used to predict log K and log P values
for the solute in any IL solvent for which the lowercase equation coefficients (cp,il, ep,il, sp,il, ap,il,
bp,il, vp,il, ck,il, ek,il, sk,il, ak,il, bk,il and lk,il) are known. The equation coefficients are unique to the IL
solvent, and provide information regarding the IL properties, such as polarity, polarisability and
hydrogen-bonding character. To date IL-specific equation coefficients have been calculated for
more than 70 ILs. See Table 1 for a list of the published equation coefficients for the various IL
solvents that have been studied thus far. Included in the tabulation is the statistical information
associated with each Abraham model correlation expression, which includes: the standard devia-
tion (SD) and the number of experimental data points used in the regression analysis (N) to
calculate the equation coefficients. The ionic liquids are listed according to the cation and anion
abbreviation (see Table 2 for the names that correspond to the different abbreviations).
The predictive ability of the IL-specific version of the Abraham model (Equations (1) and (2))
is limited in applicability to only those IL solvents for which equation coefficients have been
determined. The model’s predictive ability can be increased by recognising that each term in the
log P and log K correlations corresponds to a different type of solute–IL interaction. Sprunger and
co-workers [38–40] split each type of molecular interaction into a cation contribution and anion
contribution:
2 B. JIANG ET AL.

4. Table1.IL-specificequationcoefficientsforgeneratingAbrahammodellogPandlogKequationsfordescribingsolutetransferintoanhydrousionicliquidsolvents.
IonicliquidSolvNo.cesabv/lNSD
Water-to-ionicliquidsolvent
([MBIm]+
[Tf2N]–
)1−0.0180.4160.153−1.312−4.1873.3471010.131
([MHIm]+
[Tf2N]–
)2−0.0650.0100.260−1.476−4.3133.587750.115
([M3BAm]+
[Tf2N]–
)30.047−0.0510.356−1.262−4.4003.209570.120
([MOIm]+
[BF4]–
)4−0.1150.2100.000−0.511−4.3383.617590.159
([MBIm]+
[PF6]–
)5−0.0560.1930.737−1.351−4.5263.109860.154
([4-MBPy]+
[BF4]–
)6−0.0320.4890.466−0.873−4.1432.944380.141
([MBIm]+
[BF4]–
)7−0.0820.4540.541−0.427−4.5832.961660.132
([MEIm]+
[EtSO4]–
)8−0.059−0.0130.6091.526−5.0542.894480.138
([MEIm]+
[Tf2N]–
)90.0290.3510.202−1.684−3.5853.059640.119
([M2EIm]+
[Tf2N]–
)100.0950.2990.360−1.906−3.8053.177380.131
([4-MBPy]+
[Tf2N]–
)11−0.192−0.2191.326−1.021−4.4293.545370.120
([MBIm]+
[OtSO4]–
)12−0.0500.1980.1791.146−5.1544.008550.179
([PM2Im]+
[BF4]–
)13−0.6030.7990.8240.883−4.4172.636340.130
([MBIm]+
[Trif]–
)14−0.2200.2090.4790.066−4.3143.294520.124
([D2MIm]+
[Tf2N]–
)15−0.093−0.0520.040−1.620−4.6674.034400.118
([MOIm]+
[PF6]–
)160.085−0.1230.000−1.255−4.0883.509470.156
([EtOHMIm]+
[Tf2N]–
)17−0.4020.3040.470−1.082−3.5122.977790.133
([EtOHMIm]+
[PF6]–
)18−0.541−0.1451.102−0.596−3.6842.723360.169
([HexM3Am]+
[Tf2N]–
)19−0.3220.2420.287−1.383−4.2653.513900.138
([EMIm]+
[N(CN)2]–
)20−0.3290.3260.9090.933−4.5402.904720.127
([(Hexom)2Im]+
[Tf2N]–
)210.107−0.6280.747−1.441−4.8083.750340.106
([HexomMIm]+
[Tf2N]–
)22−0.039−0.6451.184−1.374−4.7793.609340.108
([CNPrMIm]+
[N(CN)2]–
)23−0.9280.3731.2241.042−4.3073.046440.150
([MeoeMIm]+
[Tf2N]–
)24−0.1500.0120.818−1.289−4.2633.116490.129
([(Meo)2Im]+
[Tf2N]–
)25−0.412−0.1040.761−1.124−3.7763.055460.103
([MEIm]+
[E2PO4]–
)260.0220.2890.4343.796−5.0413.346380.165
([H3TdP]+
[Tf2N]–
)27−0.1550.163−0.0291.271−5.0424.246590.136
([Et3S]+
[Tf2N]–
)28−0.062−1.3472.716−1.350−5.2743.242310.097
([3-MBPy]+
[Trif]–
)29−0.088−0.1101.1210.330−5.1883.310360.121
([MEIm]+
[B(CN)4]–
)30−0.151−0.1111.141−0.875−4.6823.002410.118
([HMIm]+
[FAP]–
)310.0670.1500.254−2.530−4.0143.446840.159
([EMIm]+
[FAP]–
)320.0930.4480.027−2.667−3.6733.082660.163
([1-PrOHPy]+
[FAP]–
)33−0.0980.2940.393−2.160−2.7852.961760.161
([PMPip]+
[Tf2N]–
)34−0.2310.4530.352−1.263−4.2903.401780.153
([BMPyrr]+
[SCN]–
)35−0.3680.7280.6241.587−4.7153.104640.177
([EMIm]+
[MeSO3]–
)36−0.7990.4930.6442.842−4.4403.007400.189
([MDIm]+
[B(CN)4]–
)370.108−0.1380.742−1.279−4.6673.526420.116
([H3TdP]+
[OtSO4]–
)380.138−0.077−0.2481.073−5.0284.037380.149
([1-PrOHPy]+
[Tf2N]–
)39−0.117−0.0341.056−0.934−4.1472.922450.113
(Continued)
PHYSICS AND CHEMISTRY OF LIQUIDS 3

5. Table1.(Continued).
IonicliquidSolvNo.cesabv/lNSD
([BMPyrr]+
[B(CN)4]–
)40−0.0710.3540.562−1.030−4.4153.346800.139
([BMPip]+
[Tf2N]–
)41−0.1290.4940.235−1.165−4.3853.422780.162
([BMIm]+
[BETI]–
)420.0230.0830.334−1.701−4.2363.041510.110
([BMIm]+
[N(CN)2]–
)43−0.2720.4480.7221.103−4.4373.131670.118
([BMPyrr]+
[FAP]–
)440.1000.2270.392−2.607−4.2853.245900.156
([BMPyrr]+
[Trif]–
)45−0.3660.4480.6280.362−4.4693.327650.134
([MHIm]+
[B(CN)4]–
)460.0000.1190.730−1.083−4.4313.389560.108
([MeoeMPip]+
[Tf2N]–
)47−0.0680.1260.726−1.122−4.6423.276590.118
([MeoeMMorp]+
[FAP]–
)480.0000.0000.830−2.362−4.0223.064990.164
([MeoeMMorp]+
[Tf2N]–
)49−0.1880.0940.918−1.180−4.3463.043620.119
([MeoeMPyrr]+
[FAP]–
)500.1300.1680.477−2.483−4.2453.2151020.158
([MeoeMPip]+
[FAP]–
)510.1140.2600.391−2.448−4.2453.2811030.163
([BMPyrr]+
[C(CN)3]–
)52−0.1260.4300.3980.000−4.5633.333950.120
([MeoeM2EAm]+
[FAP]–
)530.0340.1190.628−2.408−4.0703.1561050.149
([EtOHMIm]+
[FAP]–
)540.0000.1110.490−2.383−2.5232.8581020.140
([MBIm]+
[TDI]–
)55−0.0320.0990.616−0.254−4.4993.496660.107
([3-MBPy]+
[TDI]–
)56−0.0620.2780.544−0.833−4.5173.586660.113
[(H3TdP]+
[L-Lact]–
)570.0000.0000.0003.241−5.3294.158310.158
[(H3TdP]+
[+CS]–
)580.0000.0000.2292.749−5.3434.555400.125
([MB3Am]+
[Tf2N]–
)59−0.2330.0000.404−1.313−4.5423.687440.113
([OM3Am]+
[Tf2N]–
)60−0.165−0.1810.569−1.419−4.6773.711440.123
([DM3Am]+
[Tf2N]–
)61−0.128−0.1310.329−1.458−4.5503.816460.132
[(O4Am]+
[Tf2N]–
)620.2260.000−0.212−1.756−4.7393.825420.164
([PMPyrr]+
[Tf2N]–
)63−0.2360.0000.908−1.015−4.6913.446390.143
([BMPyrr]+
[Tf2N]–
)64−0.2690.0000.747−1.094−4.5943.512430.133
([PeMPyrr]+
[Tf2N]–
)65−0.3030.0000.727−1.107−4.6223.630420.132
([HMPyrr]+
[Tf2N]–
)66−0.226−0.0830.560−1.301−4.5013.673360.123
([OMPyrr]+
[Tf2N]–
)67−0.2530.0000.520−1.460−4.6963.815370.102
([DMPyrr]+
[Tf2N]–
)68−0.083−0.1420.419−1.467−4.8593.824400.108
([QUIN6]+
[Tf2N]–
)69−0.3600.1380.594−0.936−4.7763.864430.133
([QUIN8]+
[Tf2N]–
)70−0.1490.0000.451−1.080−4.8863.861430.133
([BM2Im]+
[Tf2N]–
)71−0.3470.1110.718−1.195−4.4183.502600.121
([4-CNBPy]+
[Tf2N]–
)72−0.3160.1321.015−1.040−4.3993.272640.123
([4-MBPy]+
[C(CN)3]–
)73−0.8000.9102.1002.3502.0702.990330.170
([MBIm]+
[C(CN)3]–
)74−0.7000.7302.0301.9301.6402.780330.120
Gas-to-ionicliquidsolvent
([MBIm]+
[Tf2N]–
)1−0.3940.0891.9692.2830.8730.6961040.111
([MHIm]+
[Tf2N]–
)2−0.384−0.2402.0602.1840.5610.754770.117
([M3BAm]+
[Tf2N]–
)3−0.4570.0002.1882.3750.6630.668580.120
([MOIm]+
[BF4]–
)4−0.409−0.0491.5622.9110.8030.778610.140
(Continued)
4 B. JIANG ET AL.

6. Table1.(Continued).
IonicliquidSolvNo.cesabv/lNSD
([MBIm]+
[PF6]–
)5−0.460−0.1912.7472.2280.3630.663910.154
([4-MBPy]+
[BF4]–
)6−0.6110.4872.4843.1900.5580.606380.062
([MBIm]+
[BF4]–
)7−0.6000.3562.5343.3120.2840.604660.099
([MEIm]+
[EtSO4]–
)8−0.7090.1372.5445.2620.0420.592490.104
([MEIm]+
[Tf2N]–
)9−0.4860.0682.2962.2780.9880.651650.094
([M2EIm]+
[Tf2N]–
)10−0.5650.2142.3472.0750.8960.655380.071
([4-MBPy]+
[Tf2N]–
)11−0.522−0.1132.7772.6730.1220.741370.080
([MBIm]+
[OtSO4]–
)12−0.288−0.2871.9404.862−0.3020.880560.116
([PM2Im]+
[BF4]–
)13−1.0250.9972.7284.5250.5180.458340.126
([MBIm]+
[Trif]–
)14−0.6490.1642.2783.8500.5520.694520.105
([D2MIm]+
[Tf2N]–
)15−0.252−0.2691.6031.9460.3540.856400.082
([MOIm]+
[PF6]–
)16−0.118−0.1301.5352.1461.0250.703480.142
([EtOHMIM]+
[Tf2N]–
)17−0.7930.1392.4042.5871.3530.581810.100
([EtOHMIM]+
[PF6]–
)18−1.044−0.0423.0923.1161.1890.508370.125
([HexM3Am]+
[Tf2N]–
)19−0.469−0.0582.0852.1850.6170.689930.128
([EMIm]+
[N(CN)2]–
)20−0.9900.3792.8804.7890.4210.617750.114
[(Hexom)2Im]+
[Tf2N]–
)21−0.314−0.4792.0762.3760.2870.835340.050
([HexomMIm]+[Tf2N]–
)22−0.462−0.3972.4862.4280.3330.785340.050
([CNPrMIm]+
[N(CN)2]–
)23−1.489−0.4183.0894.8070.6260.644450.121
([MeoeMIm]+
[Tf2N]–
)24−0.5090.0652.4762.2710.6710.603520.108
([(Meo)2Im]+
[Tf2N]–
)25−0.762−0.0132.5572.4271.1570.584480.084
([MEIm]+
[E2PO4]–
)26−0.4120.1952.2377.432−0.0910.714380.135
([H3TdP]+
[Tf2N]–
)27−0.406−0.5761.6022.338−0.0090.959590.112
([Et3S]+
[Tf2N]–
)28−0.606−0.1962.9922.4440.3550.690310.055
([3-MBPy]+[Trif]–
)29−0.5640.0352.6973.977−0.0500.699360.070
([MEIm]+
[B(CN)4]–
)30−0.4070.1412.7432.7830.4690.625410.061
([HMIm]+
[FAP]–
)31−0.189−0.0862.0771.0900.8440.696840.122
([EMIm]+
[FAP]–
)32−0.2900.0532.1231.1060.9970.617690.150
([1-PrOHPy]+
[FAP]–
)33−0.4480.0962.4671.5631.8980.563770.136
([PMPip]+
[Tf2N]–
)34−0.4320.1452.2872.4890.4020.674790.126
([BMPyrr]+
[SCN]–
)35−0.6860.5432.6225.3520.0000.602650.130
([EMIm]+
[MeSO3]–
)36−1.3980.4852.5626.6160.4950.642420.153
([MDIm]+
[B(CN)4]–
)37−0.335−0.1762.3882.4210.3720.772420.050
([H3TdP]+
[OtSO4]–
)38−0.181−0.3201.3614.7490.0000.902390.129
([1-PrOHPy]+
[Tf2N]–
)39−0.6300.3162.5872.7581.0250.583450.061
([BMPyrr]+
[B(CN)4]–
)40−0.3870.0572.4982.6860.3430.688810.093
([BMPip]+
[Tf2N]–
)41−0.3470.1112.2422.4720.2940.687790.119
([BMIm]+
[BETI]–
)42−0.4600.1412.2061.9800.6960.613530.093
([BMIm]+
[N(CN)2]–
)43−0.7730.4352.5534.8440.5050.658670.082
([BMPyrr]+
[FAP]–
)44−0.1960.0002.2881.0780.5050.649900.127
(Continued)
PHYSICS AND CHEMISTRY OF LIQUIDS 5

7. Table1.(Continued).
IonicliquidSolvNo.cesabv/lNSD
([BMPyrr]+
[Trif]–
)45−0.6810.1772.5534.0920.2830.677660.089
([MHIm]+
[B(CN)4]–
)46−0.373−0.0222.5592.5940.4500.711560.069
([MeoeMPip]+
[Tf2N]–
)47−0.4530.0752.5192.5350.2790.672590.078
([MeoeMMorp]+
[FAP]–
)48−0.3640.0002.6451.3190.8870.595990.140
([MeoeMMorp]+
[Tf2N]–
)49−0.6480.1422.7482.4750.5940.614620.092
([MeoeMPyrr]+
[FAP]–
)50−0.1450.0002.3601.2480.5230.6291040.137
([MeoeMPip]+
[FAP]–
)51−0.1770.0002.3111.2490.5420.6551030.137
([BMPyrr]+
[C(CN)3]–
)52−0.4610.2142.4973.7010.2430.684960.080
([MeoeM2EAm]+
[FAP]–
)53−0.321−0.0712.5571.3290.7220.6311060.128
([EtOHMIm]+
[FAP]–
)54−0.4000.0002.4941.3402.2720.5421020.120
([MBIm]+
[TDI]–
)55−0.432−0.0442.3663.4660.4380.752660.067
([3-MBPy]+
[TDI]–
)56−0.4190.1042.2693.3670.4130.772660.069
[(H3TdP]+
[L-Lact]–
)57−0.191−0.3531.6226.653−0.3320.907310.135
[(H3TdP]+
[+CS]–
)58−0.201−0.4081.7276.367−0.2411.035400.118
([MB3Am]+
[Tf2N]–
)59−0.506−0.1692.1032.2980.4120.777440.083
([OM3Am]+
[Tf2N]–
)60−0.426−0.3382.2422.1950.6840.779440.092
([DM3Am]+
[Tf2N]–
)61−0.363−0.3391.9862.1440.4220.809460.102
[(O4Am]+
[Tf2N]–
)620.000−0.2871.4781.8450.1890.816420.124
([PMPyrr]+
[Tf2N]–
)63−0.4660.0002.5622.5050.2710.682390.116
([BMPyrr]+
[Tf2N]–
)64−0.5220.0002.3882.4460.3810.711430.099
([PeMPyrr]+
[Tf2N]–
)65−0.5490.0002.3172.4250.3850.747420.097
([HMPyrr]+
[Tf2N]–
)66−0.533−0.1102.1462.2780.6500.767360.088
([OMPyrr]+
[Tf2N]–
)67−0.587−0.0642.0802.1760.4860.822370.080
([DMPyrr]+
[Tf2N]–
)68−0.395−0.2411.9912.1120.2680.822400.063
([QUIN6]+
[Tf2N]–
)69−0.562−0.0712.2012.5690.2380.815430.103
([QUIN8]+
[Tf2N]–
)70−0.363−0.1862.0482.4300.1420.816430.100
([BM2Im]+
[Tf2N]–
)71−0.6410.0002.4292.6630.5210.721600.085
([4-CNBPy]+
[Tf2N]–
)72−0.7680.0862.8102.6850.5530.691640.091
([4-MBPy]+
[C(CN)3]–
)73−0.6200.5102.3003.4200.5300.720350.200
([MBIm]+
[C(CN)3]–
)74−0.7800.3652.3803.3250.7400.664350.170
([PeMPip]+
[Tf2N]–
)75−0.477−0.1862.6392.4500.1030.761410.075
([HMPip]+
[Tf2N]–
)76−0.404−0.2452.4692.3480.0750.775420.066
6 B. JIANG ET AL.

8. Table 2. Names and abbreviations of the various cations and anions contained in the different
ionic liquid solvents.
Ion abbreviation Ion name
Cation
[MEIm]+
1-methyl-3-ethylimidazolium
[MBIm]+
1-methyl-3-butylimidazolium
[MHIm]+
1-methyl-3-hexylimidazolium
[MOIm]+
1-methyl-3-octylimidazolium
[MDIm]+
1-methyl-3-decylimidazolium
[M2EIm]+
1,2-dimethyl-3-ethylimidazolium
[PM2Im]+
1-propyl-2,3-dimethylimidazolium
[D2MIm]+
1,3-didecyl-2-methylimidazolium
[HexdMIm]+
1-hexadecyl-3-methylimidazolium
[(Meo)2Im]+
1,3-dimethoxyimidazolium
[MeoeMIm]+
1-methylethylether-3-methylimidazolium
[HexomMIm]+
1-hexyloxymethyl-3-methylimidazolium
[(Hexom)2Im]+
1,3-dihexyloxymethyl-3-methylimidazolium
[EtOHMIm]+
1-ethanol-3-methylimidazolium
[CNPrMIm]+
1-(3-cyanopropyl)-3-methylimidazolium
[BM2Im]+
1-butyl-2,3-dimethylimidazolium
[3-MBPy]+
3-methyl-N-butylpyridinium
[4-MBPy]+
4-methyl-N-butylpyridinium
[NEP]+
N-ethylpyridinium
[1-PrOHPy]+
1-(3-hydroxypropyl)pyridinium
[4-CNBPy]+
4-cyano-1-butylpyridinium
[PMPyrr]+
1-propyl-1-methylpyrrolidinium
[BMPyrr]+
1-butyl-1-methylpyrrolidinium
[PeMPyrr]+
1-pentyl-1-methylpyrrolidinium
[HMPyrr]+
1-hexyl-1-methylpyrrolidinium
[OMPyrr]+
1-octyl-1-methylpyrrolidinium
[DMPyrr]+
1-decyl-1-methylpyrrolidinium
[MeoeMPyrr]+
1-(2-methylethyl)-1-methylpyrrolidinium
[PMPip]+
1-propyl-1-methylpiperidinium
[BMPip]+
1-butyl-1-methylpiperidinium
[PeMPip]+
1-pentyl-1-methylpiperidinium
[HMPip]+
1-hexyl-1-methylpiperidinium
[MeoeMPip]+
1-(2-methoxyethyl)-1-methylpiperidinium
[MeoeMMorp]+
1-(2-methoxyethyl)-1-methylmorpholinium
[M3BAm]+
trimethyl(butyl)ammonium
[MO3Am]+
methyl(trioctyl)ammonium
[MB3Am]+
methyl(tributyl)ammonium
[HexM3Am]+
hexyl(trimethyl)ammonium
[OM3Am]+
octyl(trimethyl)ammonium
[DM3Am]+
decyl(trimethyl)ammonium
[O4Am]+
tetraoctylammonium
[MeoeM2EAm]+
2-methoxyethyl(dimethyl)ethylammonium
[Et3S]+
triethylsulfonium
[MiB3P]+
methyl(triisobutyl)phosphonium
[H3TdP]+
trihexyl(tetradecyl)phosphonium
[OiQu]+
N-octylisoquinolinium
[QUIN6]+
1-hexylquinuclidinium
[QUIN8]+
1-octylquinuclidinium
Anion
[Tf2N]–
bis(trifluoromethylsulfonyl)imide
[BF4]–
tetrafluoroborate
[PF6]–
hexafluorophosphate
[SCN]–
thiocyanate
[EtSO4]–
ethylsulfate
[OtSO4]–
octylsulfate
[F3Ac]–
trifluoroacetate
[Trif]–
trifluoromethanesulfonate (triflate)
[N(CN)2]–
dicyanamide
[E2PO4]–
diethylphosphate
[NO3]–
nitrate
[FAP]–
tris(pentafluoroethyl)trifluorophosphate
(Continued)
PHYSICS AND CHEMISTRY OF LIQUIDS 7

9. log P ¼ cp;cation þ cp;anion þ ep;cation þ ep;anion
À Á
E þ sp;cation þ sp;anion
À Á
S
þ ap;cation þ ap;anion
À Á
A þ bp;cation þ bp;anion
À Á
B þ vp;cation þ vp;anion
À Á
V
(3)
log K ¼ ck;cation þ ck;anion þ ek;cation þ ek;anion
À Á
E þ sk;cation þ sk;anion
À Á
S
þ ak;cation þ ak;anion
À Á
A þ bk;cation þ bk;anion
À Á
B þ lk;cation þ lk;anion
À Á
L (4)
In other words, the lowercase equation coefficients now become cation-specific and anion-specific
numerical values, which can then be combined as a cation–anion sum to yield Abraham model
equation coefficients that would be specific for the one IL solvent containing the given cation–
anion pair combination. In some respects the treatment proposed by Sprunger and co-workers is
analogous to estimating each of the different Abraham model equation coefficients by a group
contribution or fragment group method, where the entire cation serves as one functional group in
the IL and the entire counter-anion defines the second functional group.
To date we have reported ion-specific equation coefficients for 45 different cations and 19
different anions. The most updated set of ion-specific equation coefficients was published
approximately 2 years ago.[41] Since the last update was published, we have calculated ion-
specific equation coefficients for five additional cations: 1-butyl-2,3-dimethylimidazolium,[42] 4-
cyano-1-butylpyridinium,[42] 2-methoxyethyl(dimethyl)ethylammonium,[43] 1-hexylquinuclidi-
nium,[21] 1-octylquinuclidinium [21] and for three additional anions: L-lactate,[44] (1S)-(+)-10-
camphorsulphonate,[44] and 4,5-dicyano-2-(trifluoromethyl)imidazolide.[45] The 45 different
cation and 19 different anion equation coefficients that we have determined can be combined
to give Abraham model correlations for predicting log K and log P values for 855 (45 × 19)
different IL solvents. This is significantly more IL solvents than the 76 IL solvents listed in Table 1
for which we have IL-specific Abraham model correlations. Through standard thermodynamic
relationships, the predicted log K and log P values can be converted first to infinite dilution
activity coefficients, γ1
solute:
log K ¼ log P þ log KW ¼ log
RT
γ1
solutePo
soluteVsolvent
(5)
and then to separation factors, S1
1;2:
S1
1;2 ¼
γ1
solute1
γ1
solute2
(6)
that can be used to determine whether or not a desired chemical separation can be achieved using a
particular IL solvent. In Equation (5), R is the universal gas constant, Vsolvent is the molar volume of the
IL solvent, Po
soluteis the vapour pressure of the solute at the system temperature, T is the system
temperature, and log Kw is the logarithm of the solute’s gas-to-water partition coefficient. In the
present communication we have determined Abraham model correlations from published γ1
solute and
log K data for solutes dissolved in 1-allyl-3-methylimidazolium dicyanamide ([AllMIm]+
[N(CN)2]–
),
Table 2. (Continued).
Ion abbreviation Ion name
[B(CN)4]–
tetracyanoborate
[MeSO3]–
methanesulfonate
[BETI]–
bis(pentafluoroethylsulfonyl)imide
[Tos]–
tosylate
[C(CN)3]–
tricyanomethanide
[L-Lact]–
L-lactate
[+CS]–
(1S)-(+)-10-camphorsulfonate
[TDI]–
4,5-dicyano-2-(trifluoromethyl)imidazolide
8 B. JIANG ET AL.

10. [46] 1-allyl-3-methylimidazolium bis(trifluoromethylsulphonyl)imide ([AllMIm]+
[Tf2N]–
),[47] octyl-
triethylammonium bis(trifluomethylsulphonyl)imide ([OE3Am]+
[Tf2N]–
),[48] tributylethyl-
phosphonium diethylphosphate ([B3EP]+
[E2PO4]–
)[49] and 1-butyl-1-methylmorpholinium
tricyanomethanide ([BMMorp]+
[C(CN)3]–
).[50] Also calculated as part of this study are the ion-
specific equation coefficients for [AllMIm]+
, [OE3Am]+
, [B3EP]+
and [BMMorp]+
cations.
2. Computation methodology and the partition coefficient data sets
The Abraham model has been successfully used to correlate solute transfer processes. The transfer
process might involve solute partitioning between two immiscible (or partly immiscible) phases as
would be the case for solvent extractions, or might involve solute transfer where the two phases
are physically separated from each other. The latter would be referred to as a hypothetical
partition coefficient where the numerical value would be calculable as either a solubility ratio or
through a thermodynamic cycle, such as water-to-organic solvent partition coefficient equals the
gas-to-organic solvent partition coefficient divided by the gas-to-water partition coefficient
(P = K/Kw). A major difference between the two types of solute transfer processes is that first
involves mutually saturated phases, while the second involves the ‘neat’ liquid solvents. The water-
to-IL solvent partitioning systems that are listed in Table 1 all pertain to solute transfer into neat
IL solvents that are not saturated with water.
The data sets for ([AllMIm]+
[N(CN)2]–
), ([AllMIm]+
[Tf2N]–
), ([OE3Am]+
[Tf2N]–
),
([B3EP]+
[E2PO4]–
) and ([BMMorp]+
[C(CN)3]–
) were constructed from published partition coeffi-
cient data for solutes dissolved in the anhydrous IL solvents. For each IL solvent the partition
coefficient measurements were performed at several temperatures slightly higher than 298.15 K. The
numerical log K (at 298.15 K) values used in the present study were calculated from the standard
thermodynamic log K vs. 1/T linear relationship based on the measured values at either 318.15 and
328,15 K for ([AllMIm]+
[Tf2N]–
), ([OE3Am]+
[Tf2N]–
) and ([BMMorp]+
[C(CN)3]–
), or 328.15 and
338.15 K for ([B3EP]+
[E2PO4]–
), or 308.15 and 318.15 K for ([AllMIm]+
[N(CN)2]–
). The foremen-
tioned temperatures were the two lowest temperatures that were studied for each of the four IL
solvents. The linear extrapolation should be valid as the measurements were performed at tempera-
tures not too far removed from the desired temperature of 298.15 K (about 40 K in the worst case).
The respective log P values for each solute–IL combination were calculated by subtracting log Kw
from the extrapolated log K values as indicated in Equation (5).
The calculated log K and log P values at 298.15 K are assembled in Tables 3–7 for solutes
dissolved in ([AllMIm]+
[N(CN)2]–
), ([AllMIm]+
[Tf2N]–
), ([B3EP]+
[E2PO4]–
), ([OE3Am]+
[Tf2N]–
)
and ([BMMorp]+
[C(CN)3]–
), respectively. Each data set contains between 49 and 63 chemically
diverse organic liquid solutes. The list of organic solutes includes alkanes, alkenes, alkynes,
aromatic and heterocyclic compounds, primary and secondary alcohols, dialkyl ethers and cyclic
ethers, alkanones, alkyl alkanoates, and nitroalkanes. We searched the published literature but was
unable to find partition coefficient or solubility data for gaseous or solid solutes in the five IL
solvents. Also collected in Tables 3–7 are the numerical solute descriptors for the organic
compounds studied in the present investigation. Numerical values of the solute descriptors in
our database are of experimental origin and are based on observed solubility data and Henry’s law
constants,[51–54] on measured gas–liquid and high-performance liquid chromatographic reten-
tion times and retention factors,[55,56] and on experimental practical partition coefficient mea-
surements for the equilibrium solute distribution between water and an immiscible (or partially
miscible) organic solvent.[57]
Calculation of the Abraham model IL-specific equation coefficients is relatively straightforward
and begins with writing a log K and log P equation for each solute–IL solvent pair. For each
equation the measured log K and log P values, as well as the five solute descriptors that appear on
the right-hand side of Equations (1) and (2), are known. This leaves only the six unknown
equation coefficients that must be calculated. The resulting set of log K equations are solved
PHYSICS AND CHEMISTRY OF LIQUIDS 9

11. Table3.Logarithmofgas-to-anhydrousILpartitioncoefficient,logK,andlogarithmofwater-to-anhydrousILpartitioncoefficient,logP,fororganicsolutesdissolvedin([AllMIm]+
[N(CN)2]–
)at
298K.
SoluteESABLVlogKlogP
Pentane0.0000.0000.0000.0002.1620.81310.2491.949
Hexane0.0000.0000.0000.0002.6680.95400.5012.321
3-Methylpentane0.0000.0000.0000.0002.5810.95400.4872.327
2,2-Dimethylbutane0.0000.0000.0000.0002.3520.95400.2942.134
Heptane0.0000.0000.0000.0003.1731.09490.7722.732
Octane0.0000.0000.0000.0003.6771.23581.0413.151
2,2,4-Trimethylpentane0.0000.0000.0000.0003.1061.23580.6642.784
Nonane0.0000.0000.0000.0004.1821.37671.3153.465
Decane0.0000.0000.0000.0004.6861.51761.6003.920
Cyclopentane0.2630.1000.0000.0002.4770.70450.8451.725
Cyclohexane0.3050.1000.0000.0002.9640.84541.1052.005
Methylcyclohexane0.2440.0600.0000.0003.3190.98631.1982.448
Cycloheptane0.3500.1000.0000.0003.7040.98631.8752.455
Cyclooctane0.4130.1000.0000.0004.3291.12722.0112.781
1-Pentene0.0930.0800.0000.0702.0470.77010.5811.811
1-Hexene0.0780.0800.0000.0702.5720.91100.8622.022
Cyclohexene0.3950.2800.0000.0902.9520.82041.5761.846
1-Heptene0.0920.0800.0000.0703.0631.05191.1092.329
1-Octene0.0940.0800.0000.0703.5681.19281.3712.781
1-Decene0.0930.0800.0000.0704.5541.47461.8683.508
1-Pentyne0.1720.2300.1200.1202.0100.72711.4711.481
1-Hexyne0.1660.2200.1000.1202.5100.86801.7411.951
1-Heptyne0.1600.2300.1200.1003.0001.00891.9852.425
1-Octyne0.1550.2200.0900.1003.5211.14982.2302.750
Benzene0.6100.5200.0000.1402.7860.71642.4251.795
Toluene0.6010.5200.0000.1403.3250.85732.7032.053
Ethylbenzene0.6130.5100.0000.1503.7780.99822.8892.309
o-Xylene0.6630.5600.0000.1603.9390.99823.1692.509
m-Xylene0.6230.5200.0000.1603.8390.99822.9632.353
p-Xylene0.6130.5200.0000.1603.8390.99822.9732.383
Propylbenzene0.6040.5000.0000.1504.2301.13913.0582.668
Isopropylbenzene0.6020.4900.0000.1604.0841.13912.9632.523
Styrene0.8490.6500.0000.1603.9080.95503.4342.484
α-Methylstyrene0.8510.6400.0000.1904.2901.09603.6082.648
Methanol0.2780.4400.4300.4700.9700.30823.059−0.681
Ethanol0.2460.4200.3700.4801.4850.44913.094−0.576
1-Propanol0.2360.4200.3700.4802.0310.59003.362−0.198
2-Propanol0.2120.3600.3300.5601.7640.59002.996−0.484
1-Butanol0.2240.4200.3700.4802.6010.73093.6500.190
(Continued)
10 B. JIANG ET AL.

12. Table3.(Continued).
SoluteESABLVlogKlogP
2-Butanol0.2170.3600.3300.5602.3380.73093.254−0.136
2-Methyl-1-propanol0.2170.3900.3700.4802.4130.73093.4560.156
tert-Butanol0.1800.3000.3100.6001.9630.73092.897−0.383
1-Pentanol0.2190.4200.3700.4803.1060.87183.9210.571
Thiophene0.6870.5700.0000.1502.8190.64112.7461.706
Tetrahydrofuran0.2890.5200.0000.4802.6360.62232.343−0.207
1,4-Dioxane0.3290.7500.0000.6402.8920.68103.187−0.523
Methyltert-butylether0.0240.2200.0000.5502.3720.87181.408−0.212
Ethyltert-butylether−0.0200.1800.0000.5902.6991.01271.213−0.057
Methyltert-amylether0.0500.2100.0000.6002.9161.01271.6750.205
Diethylether0.0410.2500.0000.4502.0150.73091.132−0.038
Dipropylether0.0080.2500.0000.4502.9541.01271.4260.536
Diisopropylether−0.0630.1700.0000.5702.5011.01271.0770.027
Dibutylether0.0000.2500.0000.4503.9241.29451.9091.219
Acetone0.1790.7000.0400.4901.6960.54702.450−0.340
2-Pentanone0.1430.6800.0000.5102.7550.82882.8120.232
3-Pentanone0.1540.6600.0000.5102.8110.82882.7860.286
Methylacetate0.1420.6400.0000.4501.9110.60572.249−0.051
Ethylacetate0.1060.6200.0000.4502.3140.74662.3410.181
Methylpropanoate0.1280.6000.0000.4502.4310.74702.4170.267
Methylbutanoate0.1060.6000.0000.4502.9430.88802.6040.524
Butanal0.1870.6500.0000.4502.2700.68802.4520.122
Acetonitrile0.2370.9000.0700.3201.7390.40422.9960.146
Pyridine0.6310.8400.0000.5203.0220.67503.4630.023
1-Nitropropane0.2420.9500.0000.3102.8940.70553.5871.137
Water0.0000.6000.5900.4600.2450.16733.938−0.752
PHYSICS AND CHEMISTRY OF LIQUIDS 11

13. Table4.Logarithmofgas-to-anhydrousILpartitioncoefficient,logK,andlogarithmofwater-to-anhydrousILpartitioncoefficient,logP,fororganicsolutesdissolvedin([AllMIm]+
[Tf2N]–
)at
298K.
SoluteESABLVlogKlogP
Hexane0.0000.0000.0000.0002.6680.95401.2663.086
3-Methylpentane0.0000.0000.0000.0002.5810.95401.2553.095
2,2-Dimethylbutane0.0000.0000.0000.0002.3520.95401.0862.926
Heptane0.0000.0000.0000.0003.1731.09491.6013.561
Octane0.0000.0000.0000.0003.6771.23581.9214.031
2,2,4-Trimethylpentane0.0000.0000.0000.0003.1061.23581.5953.715
Nonane0.0000.0000.0000.0004.1821.37672.2454.395
Decane0.0000.0000.0000.0004.6861.51762.5544.874
Cyclopentane0.2630.1000.0000.0002.4770.70451.3602.240
Cyclohexane0.3050.1000.0000.0002.9640.84541.7022.602
Methylcyclohexane0.2440.0600.0000.0003.3190.98631.8733.123
Cycloheptane0.3500.1000.0000.0003.7040.98632.1992.779
Cyclooctane0.4130.1000.0000.0004.3291.12722.6353.405
1-Pentene0.0930.0800.0000.0702.0470.77011.1802.410
1-Hexene0.0780.0800.0000.0702.5720.91101.5092.669
Cyclohexene0.3950.2800.0000.0902.9520.82042.0292.299
1-Heptene0.0920.0800.0000.0703.0631.05191.8303.050
1-Octene0.0940.0800.0000.0703.5681.19282.1693.579
1-Decene0.0930.0800.0000.0704.5541.47462.7854.425
1-Pentyne0.1720.2300.1200.1202.0100.72711.8281.838
1-Hexyne0.1660.2200.1000.1202.5100.86802.1672.377
1-Heptyne0.1600.2300.1200.1003.0001.00892.4932.933
1-Octyne0.1550.2200.0900.1003.5211.14982.8203.340
Benzene0.6100.5200.0000.1402.7860.71642.8332.203
Toluene0.6010.5200.0000.1403.3250.85733.1862.536
Ethylbenzene0.6130.5100.0000.1503.7780.99823.4452.865
o-Xylene0.6630.5600.0000.1603.9390.99823.6863.026
m-Xylene0.6230.5200.0000.1603.8390.99823.5232.913
p-Xylene0.6130.5200.0000.1603.8390.99823.5142.924
Propylbenzene0.6040.5000.0000.1504.2301.13913.7093.319
Isopropylbenzene0.6020.4900.0000.1604.0841.13913.6003.160
Styrene0.8490.6500.0000.1603.9080.95503.9142.964
α-Methylstyrene0.8510.6400.0000.1904.2901.09604.1023.142
Methanol0.2780.4400.4300.4700.9700.30822.563−1.177
Ethanol0.2460.4200.3700.4801.4850.44912.773−0.897
1-Propanol0.2360.4200.3700.4802.0310.59003.114−0.446
2-Propanol0.2120.3600.3300.5601.7640.59002.835−0.645
1-Butanol0.2240.4200.3700.4802.6010.73093.4740.014
2-Butanol0.2170.3600.3300.5602.3380.73093.141−0.249
(Continued)
12 B. JIANG ET AL.

14. Table4.(Continued).
SoluteESABLVlogKlogP
2-Methyl-1-propanol0.21700.3900.3700.4802.4130.73093.293−0.007
tert-Butanol0.1800.3000.3100.6001.9630.73092.865−0.415
1-Pentanol0.2190.4200.3700.4803.1060.87183.8220.472
Thiophene0.6870.5700.0000.1502.8190.64112.9581.918
Tetrahydrofuran0.2890.5200.0000.4802.6360.62232.8080.258
1,4-Dioxane0.3290.7500.0000.6402.8920.68103.575−0.135
Methyltert-butylether0.0240.2200.0000.5502.3720.87182.0970.477
Ethyltert-butylether−0.0200.1800.0000.5902.6991.01272.0130.743
Methyltert-amylether0.0500.2100.0000.6002.9161.01272.4270.957
Diethylether0.0410.2500.0000.4502.0150.73091.7500.580
Dipropylether0.0080.2500.0000.4502.9541.01272.1961.306
Diisopropylether−0.0630.1700.0000.5702.5011.01271.9170.867
Dibutylether0.0000.2500.0000.4503.9241.29452.8132.123
Acetone0.1790.7000.0400.4901.6960.54702.9130.123
2-Pentanone0.1430.6800.0000.5102.7550.82883.4460.866
3-Pentanone0.1540.6600.0000.5102.8110.82883.4210.921
Methylacetate0.1420.6400.0000.4501.9110.60572.7510.451
Ethylacetate0.1060.6200.0000.4502.3140.74662.9750.815
Methylpropanoate0.1280.6000.0000.4502.4310.74703.0210.871
Methylbutanoate0.1060.6000.0000.4502.9430.88803.2781.198
Butanal0.1870.6500.0000.4502.2700.68802.9480.618
Acetonitrile0.2370.9000.0700.3201.7390.40423.2650.415
Pyridine0.6310.8400.0000.5203.0220.67503.8040.364
1-Nitropropane0.2420.9500.0000.3102.8940.70553.9871.537
Water0.0000.6000.5900.4600.2450.16732.731−1.959
PHYSICS AND CHEMISTRY OF LIQUIDS 13

15. Table5.Logarithmofgas-to-anhydrousILpartitioncoefficient,logK,andlogarithmofwater-to-anhydrousILpartitioncoefficient,logP,fororganicsolutesdissolvedin([B3EP]+
[E2PO4]–
)at298K.
SoluteESABLVlogKlogP
Pentane0.0000.0000.0000.0002.1620.81311.4753.175
Hexane0.0000.0000.0000.0002.6680.95401.9293.749
3-Methylpentane0.0000.0000.0000.0002.5810.95401.8643.704
2,2-Dimethylbutane0.0000.0000.0000.0002.3520.95401.6173.457
Heptane0.0000.0000.0000.0003.1731.09492.3574.317
Octane0.0000.0000.0000.0003.6771.23582.7944.904
2,2,4-Trimethylpentane0.0000.0000.0000.0003.1061.23582.2874.407
Nonane0.0000.0000.0000.0004.1821.37673.2065.356
Decane0.0000.0000.0000.0004.6861.51763.6195.939
Cyclopentane0.2630.1000.0000.0002.4770.70451.8882.768
Cyclohexane0.3050.1000.0000.0002.9640.84542.3123.212
Methylcyclohexane0.2440.0600.0000.0003.3190.98632.5573.807
Cycloheptane0.3500.1000.0000.0003.7040.98632.8993.479
Cyclooctane0.4130.1000.0000.0004.3291.12723.4224.192
1-Pentene0.0930.0800.0000.0702.0470.77011.5322.762
1-Hexene0.0780.0800.0000.0702.5720.91101.9913.151
Cyclohexene0.3950.2800.0000.0902.9520.82042.4652.735
1-Heptene0.0920.0800.0000.0703.0631.05192.4073.627
1-Octene0.0940.0800.0000.0703.5681.19282.8284.238
1-Decene0.0930.0800.0000.0704.5541.47463.6465.286
1-Pentyne0.1720.2300.1200.1202.0100.72712.2542.264
1-Hexyne0.1660.2200.1000.1202.5100.86802.6972.907
1-Heptyne0.1600.2300.1200.1003.0001.00893.1083.548
1-Octyne0.1550.2200.0900.1003.5211.14983.5454.065
Benzene0.6100.5200.0000.1402.7860.71642.7322.102
Toluene0.6010.5200.0000.1403.3250.85733.1152.465
Ethylbenzene0.6130.5100.0000.1503.7780.99823.4622.882
o-Xylene0.6630.5600.0000.1603.9390.99823.6182.958
m-Xylene0.6230.5200.0000.1603.8390.99823.4832.873
p-Xylene0.6130.5200.0000.1603.8390.99823.4882.898
Styrene0.8490.6500.0000.1603.9080.95503.8922.942
Thiophene0.6870.5700.0000.1502.8190.64113.0241.984
Tetrahydrofuran0.2890.5200.0000.4802.6360.62232.471−0.079
1,4-Dioxane0.3290.7500.0000.6402.8920.68103.039−0.671
Methyltert-butylether0.0240.2200.0000.5502.3720.87181.9840.364
Ethyltert-butylether−0.0200.1800.0000.5902.6991.01272.1150.845
Methyltert-amylether0.0500.2100.0000.6002.9161.01272.4550.985
Diethylether0.0410.2500.0000.4502.0150.73091.6780.508
Dipropylether0.0080.2500.0000.4502.9541.01272.4321.542
Diisopropylether−0.0630.1700.0000.5702.5011.01272.0130.963
(Continued)
14 B. JIANG ET AL.

16. Table5.(Continued).
SoluteESABLVlogKlogP
Dibutylether0.0000.2500.0000.4503.9241.29453.2392.549
Acetone0.1790.7000.0400.4901.6960.54702.380−0.410
2-Pentanone0.1430.6800.0000.5102.7550.82883.0970.517
3-Pentanone0.1540.6600.0000.5102.8110.82883.0920.592
2-Hexanone0.1360.6800.0000.5103.2860.96973.5301.120
3-Hexanone0.1360.6600.0000.5103.2710.96973.4191.149
Pyridine0.6310.8400.0000.5203.0220.67503.6180.178
1-Nitropropane0.2420.9500.0000.3102.8940.70553.9871.537
Water0.0000.6000.5900.4600.2450.16734.344−0.346
PHYSICS AND CHEMISTRY OF LIQUIDS 15

17. Table6.Logarithmofgas-to-anhydrousILpartitioncoefficient,logK,andlogarithmofwater-to-anhydrousILpartitioncoefficient,logP,fororganicsolutesdissolvedin([OE3Am]+
[Tf2N]–
)at
298K.
SoluteESABLVlogKlogP
Pentane0.0000.0000.0000.0002.1620.81311.3003.000
Hexane0.0000.0000.0000.0002.6680.95401.7483.568
3-Methylpentane0.0000.0000.0000.0002.5810.95401.6823.522
2,2-Dimethylbutane0.0000.0000.0000.0002.3520.95401.4383.278
Heptane0.0000.0000.0000.0003.1731.09492.1604.120
Octane0.0000.0000.0000.0003.6771.23582.5584.668
2,2,4-Trimethylpentane0.0000.0000.0000.0003.1061.23582.1264.246
Nonane0.0000.0000.0000.0004.1821.37672.9605.110
Decane0.0000.0000.0000.0004.6861.51763.3525.672
Cyclopentane0.2630.1000.0000.0002.4770.70451.7012.581
Cyclohexane0.3050.1000.0000.0002.9640.84542.0962.996
Methylcyclohexane0.2440.0600.0000.0003.3190.98632.3353.585
Cycloheptane0.3500.1000.0000.0003.7040.98632.6493.229
Cyclooctane0.4130.1000.0000.0004.3291.12723.1493.919
1-Pentene0.0930.0800.0000.0702.0470.77011.4372.667
1-Hexene0.0780.0800.0000.0702.5720.91101.8743.034
Cyclohexene0.3950.2800.0000.0902.9520.82042.3292.599
1-Heptene0.0920.0800.0000.0703.0631.05192.2753.495
1-Octene0.0940.0800.0000.0703.5681.19282.6734.083
1-Decene0.0930.0800.0000.0704.5541.47463.4595.099
1-Pentyne0.1720.2300.1200.1202.0100.72711.9661.976
1-Hexyne0.1660.2200.1000.1202.5100.86802.3702.580
1-Heptyne0.1600.2300.1200.1003.0001.00892.7773.217
1-Octyne0.1550.2200.0900.1003.5211.14983.1703.690
Benzene0.6100.5200.0000.1402.7860.71642.9442.314
Toluene0.6010.5200.0000.1403.3250.85733.3572.707
Ethylbenzene0.6130.5100.0000.1503.7780.99823.6773.097
o-Xylene0.6630.5600.0000.1603.9390.99823.9003.240
m-Xylene0.6230.5200.0000.1603.8390.99823.7653.155
p-Xylene0.6130.5200.0000.1603.8390.99823.7443.154
Styrene0.8490.6500.0000.1603.9080.95504.1143.164
α-Methylstyrene0.8510.6400.0000.1904.2901.09604.3593.399
Methanol0.2780.4400.4300.4700.9700.30822.372−1.368
Ethanol0.2460.4200.3700.4801.4850.44912.620−1.050
1-Propanol0.2360.4200.3700.4802.0310.59003.019−0.541
2-Propanol0.2120.3600.3300.5601.7640.59002.730−0.750
1-Butanol0.2240.4200.3700.4802.6010.73093.450−0.010
2-Butanol0.2170.3600.3300.5602.3380.73093.108−0.282
2-Methyl-1-propanol0.21700.3900.3700.4802.4130.73093.249−0.051
(Continued)
16 B. JIANG ET AL.

18. Table6.(Continued).
SoluteESABLVlogKlogP
tert-Butanol0.1800.3000.3100.6001.9630.73092.804−0.476
1-Pentanol0.2190.4200.3700.4803.1060.87183.8690.519
Thiophene0.6870.5700.0000.1502.8190.64113.0391.999
Tetrahydrofuran0.2890.5200.0000.4802.6360.62232.7670.217
1,4-Dioxane0.3290.7500.0000.6402.8920.68103.378−0.332
Methyltert-butylether0.0240.2200.0000.5502.3720.87182.1400.520
Ethyltert-butylether−0.0200.1800.0000.5902.6991.01272.1260.856
Methyltert-amylether0.0500.2100.0000.6002.9161.01272.5451.075
Diethylether0.0410.2500.0000.4502.0150.73091.7830.613
Dipropylether0.0080.2500.0000.4502.9541.01272.4231.533
Diisopropylether−0.0630.1700.0000.5702.5011.01272.0480.998
Dibutylether0.0000.2500.0000.4503.9241.29453.1772.487
Acetone0.1790.7000.0400.4901.6960.54702.702−0.088
2-Pentanone0.1430.6800.0000.5102.7550.82883.4040.824
3-Pentanone0.1540.6600.0000.5102.8110.82883.4030.903
Methylacetate0.1420.6400.0000.4501.9110.60572.5540.254
Ethylacetate0.1060.6200.0000.4502.3140.74662.8610.701
Methylpropanoate0.1280.6000.0000.4502.4310.74702.9230.773
Methylbutanoate0.1060.6000.0000.4502.9430.88803.2651.185
Butanal0.1870.6500.0000.4502.2700.68802.8850.555
Acetonitrile0.2370.9000.0700.3201.7390.40423.0060.156
Pyridine0.6310.8400.0000.5203.0220.67503.7300.290
1-Nitropropane0.2420.9500.0000.3102.8940.70553.8821.432
Water0.0000.6000.5900.4600.2450.16732.456−2.234
PHYSICS AND CHEMISTRY OF LIQUIDS 17

19. Table7.Logarithmofgas-to-anhydrousILpartitioncoefficient,logK,andlogarithmofwater-to-anhydrousILpartitioncoefficient,logP,fororganicsolutesdissolvedin([BMMorp]+
[C(CN)3]–
)at
298K.
SoluteESABLVlogKlogP
Pentane0.0000.0000.0000.0002.1620.81310.5192.219
Hexane0.0000.0000.0000.0002.6680.95400.8952.715
3-Methylpentane0.0000.0000.0000.0002.5810.95400.8342.674
2,2-Dimethylbutane0.0000.0000.0000.0002.3520.95400.5512.391
Heptane0.0000.0000.0000.0003.1731.09491.2543.214
Octane0.0000.0000.0000.0003.6771.23581.5743.684
2,2,4-Trimethylpentane0.0000.0000.0000.0003.1061.23581.1193.239
Nonane0.0000.0000.0000.0004.1821.37671.9094.059
Decane0.0000.0000.0000.0004.6861.51762.1874.507
Cyclopentane0.2630.1000.0000.0002.4770.70451.1912.071
Cyclohexane0.3050.1000.0000.0002.9640.84541.5022.402
Methylcyclohexane0.2440.0600.0000.0003.3190.98631.6272.857
Cycloheptane0.3500.1000.0000.0003.7040.98632.0582.638
Cyclooctane0.4130.1000.0000.0004.3291.12722.5203.290
1-Hexene0.0780.0800.0000.0702.5720.91101.2612.421
Cyclohexene0.3950.2800.0000.0902.9520.82041.9582.228
1-Heptene0.0920.0800.0000.0703.0631.05191.5782.798
1-Octene0.0940.0800.0000.0703.5681.19281.8933.303
1-Decene0.0930.0800.0000.0704.5541.47462.5134.133
1-Pentyne0.1720.2300.1200.1202.0100.72711.7321.742
1-Hexyne0.1660.2200.1000.1202.5100.86802.0672.277
1-Heptyne0.1600.2300.1200.1003.0001.00892.3792.819
1-Octyne0.1550.2200.0900.1003.5211.14982.6803.200
Benzene0.6100.5200.0000.1402.7860.71642.7772.147
Toluene0.6010.5200.0000.1403.3250.85733.1162.466
Ethylbenzene0.6130.5100.0000.1503.7780.99823.3642.784
o-Xylene0.6630.5600.0000.1603.9390.99823.6342.974
m-Xylene0.6230.5200.0000.1603.8390.99823.4512.841
p-Xylene0.6130.5200.0000.1603.8390.99823.4432.853
Styrene0.8490.6500.0000.1603.9080.95503.8902.940
α-Methylstyrene0.8510.6400.0000.1904.2901.09604.0653.105
Methanol0.2780.4400.4300.4700.9700.30822.868−0.872
Ethanol0.2460.4200.3700.4801.4850.44912.994−0.676
1-Propanol0.2360.4200.3700.4802.0310.59003.318−0.242
2-Propanol0.2120.3600.3300.5601.7640.59002.972−0.508
1-Butanol0.2240.4200.3700.4802.6010.73093.6800.220
2-Butanol0.2170.3600.3300.5602.3380.73093.294−0.096
2-Methyl-1-propanol0.21700.3900.3700.4802.4130.73093.4730.173
tert-Butanol0.1800.3000.3100.6001.9630.73092.923−0.357
(Continued)
18 B. JIANG ET AL.

20. Table7.(Continued).
SoluteESABLVlogKlogP
Thiophene0.6870.5700.0000.1502.8190.64113.0432.003
Tetrahydrofuran0.2890.5200.0000.4802.6360.62232.6840.134
1,4-Dioxane0.3290.7500.0000.6402.8920.68103.537−0.173
Methyltert-butylether0.0240.2200.0000.5502.3720.87181.7780.158
Ethyltert-butylether−0.0200.1800.0000.5902.6991.01271.5630.293
Methyltert-amylether0.0500.2100.0000.6002.9161.01272.1000.630
Diethylether0.0410.2500.0000.4502.0150.73091.4560.286
Dipropylether0.0080.2500.0000.4502.9541.01271.8820.992
Diisopropylether−0.0630.1700.0000.5702.5011.01271.4750.425
Dibutylether0.0000.2500.0000.4503.9241.29452.4641.774
Acetone0.1790.7000.0400.4901.6960.54702.711−0.079
2-Pentanone0.1430.6800.0000.5102.7550.82883.2260.646
3-Pentanone0.1540.6600.0000.5102.8110.82883.2130.713
Methylacetate0.1420.6400.0000.4501.9110.60572.5360.236
Ethylacetate0.1060.6200.0000.4502.3140.74662.6960.536
Methylpropanoate0.1280.6000.0000.4502.4310.74702.7990.649
Methylbutanoate0.1060.6000.0000.4502.9430.88803.0370.957
Butanal0.1870.6500.0000.4502.2700.68802.8180.488
Acetonitrile0.2370.9000.0700.3201.7390.40423.1930.343
Pyridine0.6310.8400.0000.5203.0220.67503.7550.315
1-Nitropropane0.2420.9500.0000.3102.8940.70553.9311.481
Water0.0000.6000.5900.4600.2450.16733.479−1.211
PHYSICS AND CHEMISTRY OF LIQUIDS 19

21. simultaneously to give the numerical values of ck,il, ek,il, sk,il, ak,il, bk,il and lk,il that best describe the
observed gas-to-IL partition coefficient data. The equation coefficients for the set of log P
equations are solved in similar fashion to yield the numerical values of cp,il, ep,il, sp,il, ap,il, bp,il,
vp,il. The Abraham model IL-specific equation coefficients for all derived correlations were
obtained by regression analysis using the IBM SPSS Statistics Package, Version 22. The statistical
information for each derived correlation equation was also determined using the statistical soft-
ware package. Ion-specific equation coefficients for the [AllMIm]+
, [OE3Am]+
, [B3EP]+
and
[BMMorp]+
cations were calculated simply by subtracting the known anion-specific values from
the IL-specific equation coefficients (e.g. ccation = cIL – canion; ecation = eIL – eanion, etc.). The
computational procedure will be illustrated in the next section.
3. Results and discussion
The ([AllMIm]+
[N(CN)2]–
) and ([AllMIm]+
[Tf2N]–
) data sets are the two largest of the five data sets and
contain partition coefficients for 65 and 64 organic solutes, respectively. An analysis of the experimental
log P and log K values in Tables 3 and 4 yielded the following four Abraham model IL-specific
correlations:
For ([AllMIm]+
[N(CN)2]–
):
log P 298Kð Þ¼ À0:202 0:087ð Þ þ 0:360 0:083ð ÞE þ 0:780 0:099ð ÞS þ 0:790 0:122ð ÞA
À 4:475 0:095ð ÞB þ 2:621 0:076ð ÞV
with N ¼ 65; SD ¼ 0:102; R2
¼ 0:994; F ¼ 1890
À Á
(7)
log K 298Kð Þ¼ À0:815 0:060ð Þ þ 0:534 0:076ð ÞE þ 2:719 0:076ð ÞS þ 4:550 0:100ð ÞA
þ 0:450 0:079ð ÞB þ 0:514 0:018ð ÞL
with N ¼ 65; SD ¼ 0:084; R2
¼ 0:993; F ¼ 1706
À Á
(8)
For ([AllMIm]+
[Tf2N]–
):
log P 298Kð Þ¼ 0:058 0:090ð ÞE þ 0:703 0:096ð ÞS À 1:301 0:115ð ÞA À 4:343 0:103ð ÞB
þ 3:159 0:025ð ÞV
with N ¼ 64; SD ¼ 0:112; R2
¼ 0:998; F ¼ 5328
À Á
(9)
log K 298Kð Þ ¼ À0:420 0:058ð Þþ0:081 0:071ð ÞE þ 2:493 0:072ð ÞS þ 2:369 0:094ð ÞA
þ 0:599 0:074ð ÞB þ 0:643 0:017ð ÞL
with N ¼ 64; SD ¼ 0:079; R2
¼ 0:990; F ¼ 1160
À Á
(10)
The standard errors in each of the calculated equation coefficients are given in parentheses
immediately after the respective coefficient. An examination of the associated statistical informa-
tion reveals that the derived correlations provide a very good mathematical description of solute
transfer into ([AllMIm]+
[N(CN)2]–
) and ([AllMIm]+
[Tf2N]–
) as evidenced by the small standard
deviations, SD = 0.079 to 0.112 log units, near-unity squared correlation coefficients, R2
= 0.990 to
0.998, and large Fisher F-statistical values, F = 1160 to 5328, for Equations (7)–(10). Figures 1 and
2 depict a graphical comparison of the experimental log P data vs. back-calculated values based on
our derived Abraham model correlations for solutes dissolved in ([AllMIm]+
[N(CN)2]–
) and
([AllMIm]+
[Tf2N]–
), respectively. Similar comparisons of the log K values are shown in Figures
3 and 4. There are insufficient experimental data to permit a training set and test set assessment of
the predictive ability of Equations (7)–(10) by randomly splitting the entire databases in half.
The four mathematical correlations that have been obtained thus far should enable one to
predict log P and log K values for additional organic solutes dissolved in ([AllMIm]+
[N(CN)2]–
)
20 B. JIANG ET AL.

22. and ([AllMIm]+
[Tf2N]–
), provided of course that the solute’s descriptor values fall within the in
range of numerical values used in deriving Equations (7)–(10) above. Greater predictive ability
can be obtained through the ion-specific equation coefficient version of the Abraham model. The
[AllMIm]+
-specific equation coefficients can be determined using the derived correlations for
either IL solvent. From a purely mathematical standpoint it is easier to perform the calculations
using the correlations for ([AllMIm]+
[Tf2N]–
). In developing the ion-specific model, Sprunger
and co-workers [38–40] needed a reference point for calculating the numerical values for
individual ions. In an IL solvent the ions come as a cation–anion pair, and to calculate the values
for the cation one must know the values for the anion, and vice versa. To get around this problem,
the authors set all of the equation coefficients for the [Tf2N]–
anion equal to zero. Hence, the
Figure 1. Comparison of the experimental log P data and back-calculated values based on Equation (7) for solutes dissolved in
([AllMIm]+
[N(CN)2]–
).
Figure 2. Comparison of the experimental log P data and back-calculated values based on Equation (9) for solutes dissolved in
([AllMIm]+
[Tf2N]–
).
PHYSICS AND CHEMISTRY OF LIQUIDS 21

23. coefficients in Equations (9) and (10) are not only the IL-specific equation coefficients for the
entire ([AllMIm]+
[Tf2N]–
) IL solvent, but also the ion-specific equation coefficients for the
[AllMIm]+
cation.
Alternatively, one can calculate the ion-specific equation coefficients for the [AllMIm]+
cation
from Equations (7) and (8) as log P and log K equation coefficients for the [N(CN)2]] –
anion are
known: (cp,anion = –0.257; ep,anion = 0.164; sp,anion = 0.446; ap,anion = 2.217; bp,anion = –0.256 and
vp,anion = –0.243) and (ck,anion = –0.372; ek,anion = 0.345; sk,anion = 0.476; ak,anion = 2.270; bk,anion =
–0.198 and lk,anion = –0.055).[41] We have summarised in Table 8 the results of this computation.
We have taken the average of the two sets of calculations as the [AllMIm]+
-specific equation
Figure 3. Comparison of the experimental log K data and back-calculated values based on Equation (8) for solutes dissolved in
([AllMIm]+
[N(CN)2]–
).
Figure 4. Comparison of the experimental log K data and back-calculated values based on Equation (10) for solutes dissolved
in ([AllMIm]+
[Tf2N]–
).
22 B. JIANG ET AL.

24. coefficients for the log P and log K correlations. The average [AllMIm]+
-specific equation
coefficients have been summed with the respective [Tf2N]–
-specific and [N(CN)2]–
-specific
equation coefficients to constructive predictive Abraham model correlations for both
([AllMIm]+
[N(CN)2]–
) and ([AllMIm]+
[Tf2N]–
). The log K correlations predicted the experimen-
tal values in Tables 3 and 4 to within standard errors (SE) of 0.179 log units and 0.177 log units,
respectively. Standard errors corresponding to the log P predictions were SE = 0.183 log units and
SE = 0.189 log units for ([AllMIm]+
[N(CN)2]–
) and ([AllMIm]+
[Tf2N]–
), respectively. Standard
errors are slightly larger for the log P predictions because of the added uncertainties in the log Kw
values that were used to convert the experimentally determined gas-to-IL partition coefficients to
water-to-IL partition coefficients. The computations are in accord with our earlier observations in
that the best predictions are obtained using the IL-specific Abraham model correlations, which for
these two ILs would be Equations (7)–(10).
We suspect that we can improve on the predictions by recalculating the equation coefficients
for the [N(CN)2]–
anion. Recently published experimental data for solutes dissolved in 1-butyl-3-
methylimidazolium dicyanamide [19] and 1-butyl-4-methylpyridiniun dicyanamide [58] would
nearly double the number of data points for IL solvents containing the [N(CN)2]–
anion.
Reanalysis would be a massive computation task, however, as it would require regression analysis
on our entire IL database. The last regression analysis of the entire IL database was done just over
2 years ago,[41] and at the time there were 3731 experimental log P values and 3786 experimental
log K values. It is not computationally feasible to perform a complete reanalysis every time that a
new cation or anion is added to the database. A complete reanalysis will change most (if not all) of
the existing values that have been calculated for the 40 cations and 16 anions that were in the
database when the values were last updated. It will be difficult for readers to keep track of the
latest set of equation coefficients. We prefer to update values every few years whenever there has
been sufficient new experimental values added to the large database to warrant the computational
effort.
The ([B3EP]+
[E2PO4]–
) data set is the smallest of the five IL data sets, and it contains
experimental partition coefficients for only 49 solutes. Preliminary regression analysis of the
experimental data in Table 5 gave an Abraham model log K correlation:
log K 298Kð Þ¼ À0:279 0:074ð Þ À 0:441 0:097ð ÞE þ 1:952 0:104ð ÞS þ 5:698 0:190ð ÞA
À 0:382 0:105ð ÞB þ 0:823 0:022ð ÞL
with N ¼ 49; SD ¼ 0:089; R2
¼ 0:984; F ¼ 543:2
À Á
(11)
which had a negative numerical value for the bk,il coefficient. A negative bk,il coefficient is not
realistic as this would indicate that the H-bond acidity of ([B3EP]+
[E2PO4]–
) is less than that of
Table 8. Summary of determination of the ion-specific equation coefficients for the [AllMIm]+
cation.
IL Solvent/ion Property c e s a b v l
([AllMIm]+
[Tf2N]–
) log P 0.000 0.058 0.703 −1.301 −4.344 3.159
[AllMIm]+
log P 0.000 0.058 0.703 −1.301 −4.344 3.159
([AllMIm]+
[N(CN)2]–
) log P −0.202 0.360 0.780 0.789 −4.475 2.621
[N(CN)2]–
log P −0.257 0.164 0.446 2.217 −0.256 −0.243
[AllMIm]+
log P 0.055 0.196 0.334 −1.428 −4.219 2.864
Average for [AllMIm]+
log P 0.028 0.127 0.519 −1.365 −4.282 3.012
([AllMIm]+
[Tf2N]–
) log K −0.420 0.081 2.493 2.368 0.599 0.643
[AllMIm]+
log K −0.420 0.081 2.493 2.368 0.599 0.643
([AllMIm]+
[N(CN)2]–
) log K −0.815 0.534 2.719 4.550 0.450 0.514
[N(CN)2]–
log K −0.372 0.345 0.476 2.270 −0.198 −0.055
[AllMIm]+
log K −0.443 0.189 2.243 2.280 0.648 0.569
Average for [AllMIm]+
log K −0.432 0.135 2.368 2.324 0.624 0.606
PHYSICS AND CHEMISTRY OF LIQUIDS 23

25. the gas phase. We removed the bk,il·B from Equation (11), and re-analysed all of the experimental
data in Table 5. The final Abraham model correlations,
log P 298Kð Þ ¼ 0:120 0:127ð Þ À 0:242 0:137ð ÞE þ 0:309 0:153ð ÞS þ 1:899 0:269ð ÞA
À 5:345 0:150ð ÞB þ 3:723 0:110ð ÞV
with N ¼ 49; SD ¼ 0:128; R2
¼ 0:994; F ¼ 1389
À Á
(12)
log K 298Kð Þ ¼ À0:357 0:080ð Þ À 0:224 0:086ð ÞE þ 1:663 0:073ð ÞS þ 5:859 0:209ð ÞA
þ 0:844 0:025ð ÞL
with N ¼ 49; SD ¼ 0:102; R2
¼ 0:980; F ¼ 527:8
À Á
(13)
describe the partitioning behaviour of 49 organic solutes into ([B3EP]+
[E2PO4]–
) to within a
standard deviation of 0.128 log units. As an informational note, there was very little loss in
descriptive ability by removing the bk,il·B term from the log K equation. The standard deviation
was SD = 0.089 log units with the term included in the correlation vs. SD = 0.102 log units
without the term. Ion-specific equation coefficients are available in the published literature [41]
for the [E2PO4]–
anion: (cp,anion = 0.071; ep,anion = 0.073; sp,anion = 0.006; ap,anion = 5.089; bp,anion
= –0.832 and vp,anion = 0.184) and (ck,anion = 0.093; ek,anion = 0.107; sk,anion = –0.068; ak,anion = 5.071;
bk,anion = –0.774 and lk,anion = 0.061). Subtraction of the anion-specific equation coefficients from
the respective coefficients in Equations (12) and (13) results in the following set of coefficients for
the [B3EP]+
cation: (cp,cation = 0.049; ep,cation = –0.315; sp,cation = 0.303; ap,cation = –3.190; bp,cation
= –4.513 and vp,cation = 3.539) and (ck,cation = –0.450; ek,cation = –0.331; sk,cation = 1.731; ak,cation
= 0.788; bk,cation = 0.774 and lk,cation = 0.783).
The experimental partition coefficient data in Tables 6 and 7 were analysed in a similar fashion
to yield the following two sets of Abraham model IL-specific correlations:
For ([OE3Am]+
[Tf2N]–
):
log P 298Kð Þ ¼ À0:044 0:096ð Þ þ 0:111 0:091ð ÞE þ 0:398 0:108ð ÞS À 1:298 0:133ð ÞA
À 4:815 0:103ð ÞB þ 3:667 0:085ð ÞV
with N ¼ 63; SD ¼ 0:110; R2
¼ 0:996; F ¼ 3022
À Á
(14)
log K 298Kð Þ ¼ À0:378 0:053ð Þ À 0:074 0:066ð ÞE þ 2:088 0:066ð ÞS þ 2:368 0:087ð ÞA
þ 0:166 0:068ð ÞB þ 0:792 0:016ð ÞL
with N ¼ 63; SD ¼ 0:073; R2
¼ 0:990; F ¼ 1075
À Á
(15)
For ([BMMorp]+
[C(CN)3]–
):
log P 298Kð Þ ¼ À0:318 0:088ð Þ þ 0:374 0:093ð ÞE þ 0:951 0:104ð ÞS À 4:484 0:101ð ÞB
þ 3:122 0:076ð ÞV
with N ¼ 61; SD ¼ 0:114; R2
¼ 0:994; F ¼ 2243
À Á
(16)
log K 298Kð Þ ¼ À0:774 0:067ð Þ þ 0:371 0:078ð ÞE þ 2:762 0:078ð ÞS þ 3:707 0:109ð ÞA
þ 0:452 0:080ð ÞB þ 0:643 0:020ð ÞL
with N ¼ 61; SD ¼ 0:086; R2
¼ 0:991; F ¼ 1269
À Á
(17)
As an informational note, the ap,il·A term made a negligible contribution to the overall log P
correlation. The calculated ap,il coefficient was very small (0.021) and the standard error in the
coefficient was approximately seven times larger than the coefficient itself. Equations (14)–(17)
provide reasonably accurate mathematical descriptions of the observed log P and log K values for
solute transfer into both ([OE3Am]+
[Tf2N]–
) and ([BMMorp]+
[C(CN)3]–
). There is insufficient
24 B. JIANG ET AL.

26. experimental data to perform training set and test set analyses by splitting the data sets in half.
Based on our past experience in deriving and using Abraham model correlations for IL solvents,
however, we fully expect that Equations (14)–(17) will allow one to predict log P and log K values
for additional organic solutes to within approximately 0.13 log units of the observed values.
As noted above, for IL solvents that contain the [Tf2N]–
anion the calculated equation
coefficients pertain not only the entire IL solvent, but to the cation as well. The coefficients that
are given in Equations (14) and (15) are the ion-specific equation coefficients for the [OE3Am]+
cation. Determination of the ion-specific equation coefficients for [BMMorp]+
is slightly more
involved and requires knowledge of the equation coefficients for the [C(CN)3]–
anion, which are
available in the published tabulations in the paper by Stephens and co-workers.[41] The equation
coefficients for the [C(CN)3]–
anion are: (cp,anion = –0.079; ep,anion = 0.056; sp,anion = 0.276; ap,anion
= 1.223; bp,anion = –0.070 and vp,anion = –0.008) and (ck,anion = –0.098; ek,anion = 0.094; sk,anion
= 0.290; ak,anion = 1.338; bk,anion = –0.145 and lk,anion = 0.005). Subtraction of the anion-specific
equation coefficients from the respective coefficients in Equations (16) and (17) results in the
following set of coefficients for the [BMMorp]+
cation: (cp,cation = –0.239; ep,cation = 0.318; sp,cation
= 0.675; ap,cation = –1.223; bp,cation = –4.414 and vp,cation = 3.130) and (ck,cation = –0.676; ek,cation
= 0.277; sk,cation = 2.472; ak,cation = 2.369; bk,cation = 0.597 and lk,cation = 0.638). The calculated
cation-specific equation coefficients can be combined with the 19 anion-specific equation coeffi-
cients that we have previously determined.[41,44,45] For each of the four cations that we have
studied in the present communication, we can build log K and log P Abraham model predictive
correlations for an additional 19 different IL solvents. This increases the Abraham model’s
predictive capability by an additional 76 different IL solvents.
4. Conclusion
The Abraham model has been shown to provide very good mathematical descriptions of the
water-to-anhydrous IL and gas-to-anhydrous IL partition coefficients for solutes dissolved in
([AllMIm]+
[N(CN)2]–
), ([AllMIm]+
[Tf2N]–
), ([B3EP]+
[E2PO4]–
), ([OE3Am]+
[Tf2N]–
) and
([BMMorp]+
[C(CN)3]–
). The derived correlations back-calculate the observed partition coefficient
data to within standard deviations from SD = 0.073 log units to SD = 0.128 log units. As part of
the present communication, cation-specific equation coefficients have been calculated for
[AllMIm]+
, [OE3Am]+
, [B3EP]+
and [BMMorp]+
. For each of the four cations that we have
studied in the present communication, we can build log K and log P Abraham model predictive
correlations for an additional 19 different IL solvents. This increases the Abraham model’s
predictive capability by an additional 76 different IL solvents.
Acknowledgements
Bihan Jiang and Melissa Horton thank the University of North Texas’s Texas Academy of Math and Science
(TAMS) program for a summer research award.
Disclosure statement
No potential conflict of interest was reported by the authors.
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