Ion specific equation coefficient version of the Abraham model for ionic liquid solvents...

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Physics and Chemistry of LiquidsAn International Journal

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Ion-specific equation coefficient versionof the Abraham model for ionic liquidsolvents: determination of coefficientsfor tributylethylphosphonium, 1-butyl-1-methylmorpholinium, 1-allyl-3-methylimidazoliumand 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 ofLiquids, DOI: 10.1080/00319104.2016.1218009

To link to this article: http://dx.doi.org/10.1080/00319104.2016.1218009

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Ion-specific equation coefficient version of the Abraham modelfor ionic liquid solvents: determination of coefficients fortributylethylphosphonium, 1-butyl-1-methylmorpholinium,1-allyl-3-methylimidazolium and octyltriethylammonium cationsBihan Jianga, Melissa Y. Hortona, William E. Acree Jr.a and Michael H. Abrahamb

aDepartment of Chemistry, University of North Texas, Denton, TX, USA; bDepartment of Chemistry, UniversityCollege London, London, UK

ABSTRACTGas-to-ionic liquid partition coefficient data have been assembled fromthe 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 coefficientsusing standard thermodynamic relationships. Both sets of partition coeffi-cients were correlated with the Abraham solvation parameter model. Thederived Abraham model correlations described the observed partitioncoefficient data to within 0.13 log units. Cation-specific equation coeffi-cients were calculated for each of the cations present in the five ionicliquid solvents studied. The calculated cation-specific equation coefficientscan be combined with previously reported ion-specific equation coeffi-cients for 19 different anions to yield Abraham model correlations forpredicting the partitioning the behaviour of solutes in 76 different anhy-drous ionic liquid solvents.

ARTICLE HISTORYReceived 30 June 2016Accepted 25 July 2016

KEYWORDSIonic liquid solvents;partition coefficients; solutetransfer processes; Abrahammodel correlations

1. Introduction

Ionic liquid (IL) solvents have been successfully employed in separation processes involving theremoval 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) andcombustion organic gas (methane, ethane, ethene, acetylene) samples,[7–11] and removal of acidicgases (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 solventshave towards absorbing various organic compounds and separation factors that IL solvents exhibitfor performing various practical chemical separations. Selectivity factors have been measured andcompiled 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]) separationsbased on experimentally determined infinite dilution activity coefficients, γ1solute, for the respectivesolutes dissolved in the IL solvents. While the observed thermodynamic data provide valuableinformation regarding whether the desired chemical separation can be achieved using the IL

CONTACT William E. Acree, Jr. [email protected]© 2016 Informa UK Limited, trading as Taylor & Francis Group

PHYSICS AND CHEMISTRY OF LIQUIDS, 2016http://dx.doi.org/10.1080/00319104.2016.1218009

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solvents studied, it is not practical to perform measurements for every organic solute pair dissolvedin 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 haveturned 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 designcomputations. Predictive methods have involved both theoretical and semi-theoretical treatments,as well as approaches based on group contribution and molecular fragment schemes, linear freeenergy relationships (LFERs) and quantitative structure–property relationships (QSPRs). Groupcontribution methods have been proposed, which enable one to predict infinite dilution activitycoefficients and gas–to-liquid partition coefficients of solutes dissolved in ILs,[24–26] to predictenthalpies 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 theentire cation was defined as one functional group and the entire counter-anion was defined as asecond functional group.

Our contribution towards facilitating the use of IL solvents in chemical separation processeshas been to develop mathematical correlations based on the Abraham model that enable one topredict 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;il�E þ sp;il�S þ ap;il�A þ bp;il�B þ vp;il�V (1)

or solute transfer to a condensed phase from the vapour phase:

log K ¼ ck;il þ ek;il�Eþ sk;il�Sþ ak;il�Aþ bk;il�Bþ lk;il�L (2)

In the present study one of the condensed phases is the IL solvent. Equation (1) will thus describethe water-to-IL solvent partition coefficient, log P, while Equation (2) will describe the gas-to-ILpartition 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 areunique to a given solute molecule. Solute descriptors are defined as follows: the solute excessmolar refractivity in units of (cm3 mol–1)/10 (E), the solute dipolarity/polarisability (S), the overallor summation hydrogen-bond acidity and basicity (A and B, respectively), the McGowan volumein units of (cm3 mol–1)/100 (V), and the logarithm of the gas-to-hexadecane partition coefficientat 298 K (L). Once calculated, the solute descriptors can be used to predict log K and log P valuesfor 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 ILsolvent, and provide information regarding the IL properties, such as polarity, polarisability andhydrogen-bonding character. To date IL-specific equation coefficients have been calculated formore than 70 ILs. See Table 1 for a list of the published equation coefficients for the various ILsolvents that have been studied thus far. Included in the tabulation is the statistical informationassociated 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) tocalculate the equation coefficients. The ionic liquids are listed according to the cation and anionabbreviation (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 beendetermined. The model’s predictive ability can be increased by recognising that each term in thelog P and log K correlations corresponds to a different type of solute–IL interaction. Sprunger andco-workers [38–40] split each type of molecular interaction into a cation contribution and anioncontribution:

2 B. JIANG ET AL.

Table1.

IL-specific

equatio

ncoefficientsforgeneratin

gAb

raham

mod

ellogPandlogKequatio

nsfordescrib

ingsolute

transfer

into

anhydrou

sionicliquidsolvents.

Ionicliquid

SolvNo.

ce

sa

bv/l

NSD

Water-to-ionicliquidsolvent

([MBIm]+[Tf 2N]–)

1−0.018

0.416

0.153

−1.312

−4.187

3.347

101

0.131

([MHIm]+[Tf 2N]–)

2−0.065

0.010

0.260

−1.476

−4.313

3.587

750.115

([M3BAm

]+[Tf 2N]–)

30.047

−0.051

0.356

−1.262

−4.400

3.209

570.120

([MOIm]+[BF 4]–)

4−0.115

0.210

0.000

−0.511

−4.338

3.617

590.159

([MBIm]+[PF 6]–)

5−0.056

0.193

0.737

−1.351

−4.526

3.109

860.154

([4-M

BPy]+[BF 4]–)

6−0.032

0.489

0.466

−0.873

−4.143

2.944

380.141

([MBIm]+[BF 4]–)

7−0.082

0.454

0.541

−0.427

−4.583

2.961

660.132

([MEIm]+[EtSO4]–)

8−0.059

−0.013

0.609

1.526

−5.054

2.894

480.138

([MEIm]+[Tf 2N]–)

90.029

0.351

0.202

−1.684

−3.585

3.059

640.119

([M2EIm]+[Tf 2N]–)

100.095

0.299

0.360

−1.906

−3.805

3.177

380.131

([4-M

BPy]+[Tf 2N]–)

11−0.192

−0.219

1.326

−1.021

−4.429

3.545

370.120

([MBIm]+[OtSO4]–)

12−0.050

0.198

0.179

1.146

−5.154

4.008

550.179

([PM2Im]+[BF 4]–)

13−0.603

0.799

0.824

0.883

−4.417

2.636

340.130

([MBIm]+[Trif]–)

14−0.220

0.209

0.479

0.066

−4.314

3.294

520.124

([D2M

Im]+[Tf 2N]–)

15−0.093

−0.052

0.040

−1.620

−4.667

4.034

400.118

([MOIm]+[PF 6]–)

160.085

−0.123

0.000

−1.255

−4.088

3.509

470.156

([EtOHMIm]+[Tf 2N]–)

17−0.402

0.304

0.470

−1.082

−3.512

2.977

790.133

([EtOHMIm]+[PF 6]–)

18−0.541

−0.145

1.102

−0.596

−3.684

2.723

360.169

([HexM3Am]+[Tf 2N]–)

19−0.322

0.242

0.287

−1.383

−4.265

3.513

900.138

([EMIm]+[N(CN) 2]–)

20−0.329

0.326

0.909

0.933

−4.540

2.904

720.127

([(Hexom

) 2Im]+[Tf 2N]–)

210.107

−0.628

0.747

−1.441

−4.808

3.750

340.106

([Hexom

MIm]+[Tf 2N]–)

22−0.039

−0.645

1.184

−1.374

−4.779

3.609

340.108

([CNPrMIm]+[N(CN) 2]–)

23−0.928

0.373

1.224

1.042

−4.307

3.046

440.150

([MeoeM

Im]+[Tf 2N]–)

24−0.150

0.012

0.818

−1.289

−4.263

3.116

490.129

([(Meo) 2Im]+[Tf 2N]–)

25−0.412

−0.104

0.761

−1.124

−3.776

3.055

460.103

([MEIm]+[E2PO4]–)

260.022

0.289

0.434

3.796

−5.041

3.346

380.165

([H3TdP

]+[Tf 2N]–)

27−0.155

0.163

−0.029

1.271

−5.042

4.246

590.136

([Et 3S]+[Tf 2N]–)

28−0.062

−1.347

2.716

−1.350

−5.274

3.242

310.097

([3-M

BPy]+[Trif]–)

29−0.088

−0.110

1.121

0.330

−5.188

3.310

360.121

([MEIm]+[B(CN) 4]–)

30−0.151

−0.111

1.141

−0.875

−4.682

3.002

410.118

([HMIm]+[FAP

]–)

310.067

0.150

0.254

−2.530

−4.014

3.446

840.159

([EMIm]+[FAP

]–)

320.093

0.448

0.027

−2.667

−3.673

3.082

660.163

([1-PrOHPy]+[FAP

]–)

33−0.098

0.294

0.393

−2.160

−2.785

2.961

760.161

([PMPip]

+[Tf 2N]–)

34−0.231

0.453

0.352

−1.263

−4.290

3.401

780.153

([BMPyrr]+[SCN

]–)

35−0.368

0.728

0.624

1.587

−4.715

3.104

640.177

([EMIm]+[M

eSO3]–)

36−0.799

0.493

0.644

2.842

−4.440

3.007

400.189

([MDIm]+[B(CN) 4]–)

370.108

−0.138

0.742

−1.279

−4.667

3.526

420.116

([H3TdP

]+[OtSO4]–)

380.138

−0.077

−0.248

1.073

−5.028

4.037

380.149

([1-PrOHPy]+[Tf 2N]–)

39−0.117

−0.034

1.056

−0.934

−4.147

2.922

450.113

(Con

tinued)

PHYSICS AND CHEMISTRY OF LIQUIDS 3

Table1.

(Con

tinued).

Ionicliquid

SolvNo.

ce

sa

bv/l

NSD

([BMPyrr]+[B(CN) 4]–)

40−0.071

0.354

0.562

−1.030

−4.415

3.346

800.139

([BMPip]

+[Tf 2N]–)

41−0.129

0.494

0.235

−1.165

−4.385

3.422

780.162

([BMIm]+[BETI]–)

420.023

0.083

0.334

−1.701

−4.236

3.041

510.110

([BMIm]+[N(CN) 2]–)

43−0.272

0.448

0.722

1.103

−4.437

3.131

670.118

([BMPyrr]+[FAP

]–)

440.100

0.227

0.392

−2.607

−4.285

3.245

900.156

([BMPyrr]+[Trif]–)

45−0.366

0.448

0.628

0.362

−4.469

3.327

650.134

([MHIm]+[B(CN) 4]–)

460.000

0.119

0.730

−1.083

−4.431

3.389

560.108

([MeoeM

Pip]

+[Tf 2N]–)

47−0.068

0.126

0.726

−1.122

−4.642

3.276

590.118

([MeoeM

Morp]

+[FAP

]–)

480.000

0.000

0.830

−2.362

−4.022

3.064

990.164

([MeoeM

Morp]

+[Tf 2N]–)

49−0.188

0.094

0.918

−1.180

−4.346

3.043

620.119

([MeoeM

Pyrr]+[FAP

]–)

500.130

0.168

0.477

−2.483

−4.245

3.215

102

0.158

([MeoeM

Pip]

+[FAP

]–)

510.114

0.260

0.391

−2.448

−4.245

3.281

103

0.163

([BMPyrr]+[C(CN) 3]–)

52−0.126

0.430

0.398

0.000

−4.563

3.333

950.120

([MeoeM

2EAm

]+[FAP

]–)

530.034

0.119

0.628

−2.408

−4.070

3.156

105

0.149

([EtOHMIm]+[FAP

]–)

540.000

0.111

0.490

−2.383

−2.523

2.858

102

0.140

([MBIm]+[TDI]–)

55−0.032

0.099

0.616

−0.254

−4.499

3.496

660.107

([3-M

BPy]+[TDI]–)

56−0.062

0.278

0.544

−0.833

−4.517

3.586

660.113

[(H3TdP

]+[L-Lact]–)

570.000

0.000

0.000

3.241

−5.329

4.158

310.158

[(H3TdP

]+[+CS]–)

580.000

0.000

0.229

2.749

−5.343

4.555

400.125

([MB 3Am

]+[Tf 2N]–)

59−0.233

0.000

0.404

−1.313

−4.542

3.687

440.113

([OM3Am]+[Tf 2N]–)

60−0.165

−0.181

0.569

−1.419

−4.677

3.711

440.123

([DM3Am]+[Tf 2N]–)

61−0.128

−0.131

0.329

−1.458

−4.550

3.816

460.132

[(O4Am]+[Tf 2N]–)

620.226

0.000

−0.212

−1.756

−4.739

3.825

420.164

([PMPyrr]+[Tf 2N]–)

63−0.236

0.000

0.908

−1.015

−4.691

3.446

390.143

([BMPyrr]+[Tf 2N]–)

64−0.269

0.000

0.747

−1.094

−4.594

3.512

430.133

([PeM

Pyrr]+[Tf 2N]–)

65−0.303

0.000

0.727

−1.107

−4.622

3.630

420.132

([HMPyrr]+[Tf 2N]–)

66−0.226

−0.083

0.560

−1.301

−4.501

3.673

360.123

([OMPyrr]+[Tf 2N]–)

67−0.253

0.000

0.520

−1.460

−4.696

3.815

370.102

([DMPyrr]+[Tf 2N]–)

68−0.083

−0.142

0.419

−1.467

−4.859

3.824

400.108

([QUIN6]+[Tf 2N]–)

69−0.360

0.138

0.594

−0.936

−4.776

3.864

430.133

([QUIN8]+[Tf 2N]–)

70−0.149

0.000

0.451

−1.080

−4.886

3.861

430.133

([BM2Im]+[Tf 2N]–)

71−0.347

0.111

0.718

−1.195

−4.418

3.502

600.121

([4-CNBPy]+[Tf 2N]–)

72−0.316

0.132

1.015

−1.040

−4.399

3.272

640.123

([4-M

BPy]+[C(CN) 3]–)

73−0.800

0.910

2.100

2.350

2.070

2.990

330.170

([MBIm]+[C(CN) 3]–)

74−0.700

0.730

2.030

1.930

1.640

2.780

330.120

Gas-to-ionicliquidsolvent

([MBIm]+[Tf 2N]–)

1−0.394

0.089

1.969

2.283

0.873

0.696

104

0.111

([MHIm]+[Tf 2N]–)

2−0.384

−0.240

2.060

2.184

0.561

0.754

770.117

([M3BAm

]+[Tf 2N]–)

3−0.457

0.000

2.188

2.375

0.663

0.668

580.120

([MOIm]+[BF 4]–)

4−0.409

−0.049

1.562

2.911

0.803

0.778

610.140

(Con

tinued)

4 B. JIANG ET AL.

Table1.

(Con

tinued).

Ionicliquid

SolvNo.

ce

sa

bv/l

NSD

([MBIm]+[PF 6]–)

5−0.460

−0.191

2.747

2.228

0.363

0.663

910.154

([4-M

BPy]+[BF 4]–)

6−0.611

0.487

2.484

3.190

0.558

0.606

380.062

([MBIm]+[BF 4]–)

7−0.600

0.356

2.534

3.312

0.284

0.604

660.099

([MEIm]+[EtSO4]

–)

8−0.709

0.137

2.544

5.262

0.042

0.592

490.104

([MEIm]+[Tf 2N]–)

9−0.486

0.068

2.296

2.278

0.988

0.651

650.094

([M2EIm]+[Tf 2N]–)

10−0.565

0.214

2.347

2.075

0.896

0.655

380.071

([4-M

BPy]+[Tf 2N]–)

11−0.522

−0.113

2.777

2.673

0.122

0.741

370.080

([MBIm]+[OtSO4]–)

12−0.288

−0.287

1.940

4.862

−0.302

0.880

560.116

([PM2Im]+[BF 4]–)

13−1.025

0.997

2.728

4.525

0.518

0.458

340.126

([MBIm]+[Trif]–)

14−0.649

0.164

2.278

3.850

0.552

0.694

520.105

([D2M

Im]+[Tf 2N]–)

15−0.252

−0.269

1.603

1.946

0.354

0.856

400.082

([MOIm]+[PF 6]–)

16−0.118

−0.130

1.535

2.146

1.025

0.703

480.142

([EtOHMIM]+[Tf 2N]–)

17−0.793

0.139

2.404

2.587

1.353

0.581

810.100

([EtOHMIM]+[PF 6]–)

18−1.044

−0.042

3.092

3.116

1.189

0.508

370.125

([HexM3Am]+[Tf 2N]–)

19−0.469

−0.058

2.085

2.185

0.617

0.689

930.128

([EMIm]+[N(CN) 2]–)

20−0.990

0.379

2.880

4.789

0.421

0.617

750.114

[(Hexom

) 2Im]+[Tf 2N]–)

21−0.314

−0.479

2.076

2.376

0.287

0.835

340.050

([Hexom

MIm]+[Tf 2N]–)

22−0.462

−0.397

2.486

2.428

0.333

0.785

340.050

([CNPrMIm]+[N(CN) 2]–)

23−1.489

−0.418

3.089

4.807

0.626

0.644

450.121

([MeoeM

Im]+[Tf 2N]–)

24−0.509

0.065

2.476

2.271

0.671

0.603

520.108

([(Meo) 2Im]+[Tf 2N]–)

25−0.762

−0.013

2.557

2.427

1.157

0.584

480.084

([MEIm]+[E2PO4]–)

26−0.412

0.195

2.237

7.432

−0.091

0.714

380.135

([H3TdP

]+[Tf 2N]–)

27−0.406

−0.576

1.602

2.338

−0.009

0.959

590.112

([Et 3S]+[Tf 2N]–)

28−0.606

−0.196

2.992

2.444

0.355

0.690

310.055

([3-M

BPy]+[Trif]–)

29−0.564

0.035

2.697

3.977

−0.050

0.699

360.070

([MEIm]+[B(CN) 4]–)

30−0.407

0.141

2.743

2.783

0.469

0.625

410.061

([HMIm]+[FAP

]–)

31−0.189

−0.086

2.077

1.090

0.844

0.696

840.122

([EMIm]+[FAP

]–)

32−0.290

0.053

2.123

1.106

0.997

0.617

690.150

([1-PrOHPy]+[FAP

]–)

33−0.448

0.096

2.467

1.563

1.898

0.563

770.136

([PMPip]

+[Tf 2N]–)

34−0.432

0.145

2.287

2.489

0.402

0.674

790.126

([BMPyrr]+[SCN

]–)

35−0.686

0.543

2.622

5.352

0.000

0.602

650.130

([EMIm]+[M

eSO3]–)

36−1.398

0.485

2.562

6.616

0.495

0.642

420.153

([MDIm]+[B(CN) 4]–)

37−0.335

−0.176

2.388

2.421

0.372

0.772

420.050

([H3TdP

]+[OtSO4]–)

38−0.181

−0.320

1.361

4.749

0.000

0.902

390.129

([1-PrOHPy]+[Tf 2N]–)

39−0.630

0.316

2.587

2.758

1.025

0.583

450.061

([BMPyrr]+[B(CN) 4]–)

40−0.387

0.057

2.498

2.686

0.343

0.688

810.093

([BMPip]

+[Tf 2N]–)

41−0.347

0.111

2.242

2.472

0.294

0.687

790.119

([BMIm]+[BETI]–)

42−0.460

0.141

2.206

1.980

0.696

0.613

530.093

([BMIm]+[N(CN) 2]–)

43−0.773

0.435

2.553

4.844

0.505

0.658

670.082

([BMPyrr]+[FAP

]–)

44−0.196

0.000

2.288

1.078

0.505

0.649

900.127

(Con

tinued)


Table1.

(Con

tinued).

Ionicliquid

SolvNo.

ce

sa

bv/l

NSD

([BMPyrr]+[Trif]–)

45−0.681

0.177

2.553

4.092

0.283

0.677

660.089

([MHIm]+[B(CN) 4]–)

46−0.373

−0.022

2.559

2.594

0.450

0.711

560.069

([MeoeM

Pip]

+[Tf 2N]–)

47−0.453

0.075

2.519

2.535

0.279

0.672

590.078

([MeoeM

Morp]

+[FAP

]–)

48−0.364

0.000

2.645

1.319

0.887

0.595

990.140

([MeoeM

Morp]

+[Tf 2N]–)

49−0.648

0.142

2.748

2.475

0.594

0.614

620.092

([MeoeM

Pyrr]+[FAP

]–)

50−0.145

0.000

2.360

1.248

0.523

0.629

104

0.137

([MeoeM

Pip]

+[FAP

]–)

51−0.177

0.000

2.311

1.249

0.542

0.655

103

0.137

([BMPyrr]+[C(CN) 3]–)

52−0.461

0.214

2.497

3.701

0.243

0.684

960.080

([MeoeM

2EAm

]+[FAP

]–)

53−0.321

−0.071

2.557

1.329

0.722

0.631

106

0.128

([EtOHMIm]+[FAP

]–)

54−0.400

0.000

2.494

1.340

2.272

0.542

102

0.120

([MBIm]+[TDI]–)

55−0.432

−0.044

2.366

3.466

0.438

0.752

660.067

([3-M

BPy]+[TDI]–)

56−0.419

0.104

2.269

3.367

0.413

0.772

660.069

[(H3TdP

]+[L-Lact]–)

57−0.191

−0.353

1.622

6.653

−0.332

0.907

310.135

[(H3TdP

]+[+CS]–)

58−0.201

−0.408

1.727

6.367

−0.241

1.035

400.118

([MB 3Am

]+[Tf 2N]–)

59−0.506

−0.169

2.103

2.298

0.412

0.777

440.083

([OM3Am]+[Tf 2N]–)

60−0.426

−0.338

2.242

2.195

0.684

0.779

440.092

([DM3Am]+[Tf 2N]–)

61−0.363

−0.339

1.986

2.144

0.422

0.809

460.102

[(O4Am]+[Tf 2N]–)

620.000

−0.287

1.478

1.845

0.189

0.816

420.124

([PMPyrr]+[Tf 2N]–)

63−0.466

0.000

2.562

2.505

0.271

0.682

390.116

([BMPyrr]+[Tf 2N]–)

64−0.522

0.000

2.388

2.446

0.381

0.711

430.099

([PeM

Pyrr]+[Tf 2N]–)

65−0.549

0.000

2.317

2.425

0.385

0.747

420.097

([HMPyrr]+[Tf 2N]–)

66−0.533

−0.110

2.146

2.278

0.650

0.767

360.088

([OMPyrr]+[Tf 2N]–)

67−0.587

−0.064

2.080

2.176

0.486

0.822

370.080

([DMPyrr]+[Tf 2N]–)

68−0.395

−0.241

1.991

2.112

0.268

0.822

400.063

([QUIN6]+[Tf 2N]–)

69−0.562

−0.071

2.201

2.569

0.238

0.815

430.103

([QUIN8]+[Tf 2N]–)

70−0.363

−0.186

2.048

2.430

0.142

0.816

430.100

([BM2Im]+[Tf 2N]–)

71−0.641

0.000

2.429

2.663

0.521

0.721

600.085

([4-CNBPy]+[Tf 2N]–)

72−0.768

0.086

2.810

2.685

0.553

0.691

640.091

([4-M

BPy]+[C(CN) 3]–)

73−0.620

0.510

2.300

3.420

0.530

0.720

350.200

([MBIm]+[C(CN) 3]–)

74−0.780

0.365

2.380

3.325

0.740

0.664

350.170

([PeM

Pip]

+[Tf 2N]–)

75−0.477

−0.186

2.639

2.450

0.103

0.761

410.075

([HMPip]

+[Tf 2N]–)

76−0.404

−0.245

2.469

2.348

0.075

0.775

420.066

6 B. JIANG ET AL.

Table 2. Names and abbreviations of the various cations and anions contained in the differentionic 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-octylquinuclidiniumAnion[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 )


log P ¼ cp;cation þ cp;anion þ ep;cation þ ep;anion� �

Eþ sp;cation þ sp;anion� �

S

þ ap;cation þ ap;anion� �

Aþ bp;cation þ bp;anion� �

Bþ vp;cation þ vp;anion� �

V(3)

log K ¼ ck;cation þ ck;anion þ ek;cation þ ek;anion� �

Eþ sk;cation þ sk;anion� �

S

þ ak;cation þ ak;anion� �

Aþ bk;cation þ bk;anion� �

Bþ lk;cation þ lk;anion� �

L (4)

In other words, the lowercase equation coefficients now become cation-specific and anion-specificnumerical values, which can then be combined as a cation–anion sum to yield Abraham modelequation 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 isanalogous to estimating each of the different Abraham model equation coefficients by a groupcontribution or fragment group method, where the entire cation serves as one functional group inthe 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 19different anions. The most updated set of ion-specific equation coefficients was publishedapproximately 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 differentcation and 19 different anion equation coefficients that we have determined can be combinedto 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 1for which we have IL-specific Abraham model correlations. Through standard thermodynamicrelationships, the predicted log K and log P values can be converted first to infinite dilutionactivity coefficients, γ1solute:

logK ¼ log P þ logKW ¼ logRT

γ1solutePosoluteVsolvent

� �(5)

and then to separation factors, S11;2:

S11;2 ¼γ1solute1γ1solute2

(6)

that can be used to determine whether or not a desired chemical separation can be achieved using aparticular IL solvent. In Equation (5), R is the universal gas constant,Vsolvent is themolar volume of theIL solvent, Po

soluteis the vapour pressure of the solute at the system temperature, T is the systemtemperature, and log Kw is the logarithm of the solute’s gas-to-water partition coefficient. In thepresent communication we have determined Abraham model correlations from published γ1solute andlog 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.

[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-methylmorpholiniumtricyanomethanide ([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 transferprocess might involve solute partitioning between two immiscible (or partly immiscible) phases aswould be the case for solvent extractions, or might involve solute transfer where the two phasesare physically separated from each other. The latter would be referred to as a hypotheticalpartition coefficient where the numerical value would be calculable as either a solubility ratio orthrough a thermodynamic cycle, such as water-to-organic solvent partition coefficient equals thegas-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 firstinvolves 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 neatIL 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 partitioncoefficient measurements were performed at several temperatures slightly higher than 298.15 K. Thenumerical log K (at 298.15 K) values used in the present study were calculated from the standardthermodynamic log K vs. 1/T linear relationship based on the measured values at either 318.15 and328,15 K for ([AllMIm]+[Tf2N]

–), ([OE3Am]+[Tf2N]–) and ([BMMorp]+[C(CN)3]

–), or 328.15 and338.15 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 ILsolvents. 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 cyclicethers, alkanones, alkyl alkanoates, and nitroalkanes. We searched the published literature but wasunable to find partition coefficient or solubility data for gaseous or solid solutes in the five ILsolvents. Also collected in Tables 3–7 are the numerical solute descriptors for the organiccompounds studied in the present investigation. Numerical values of the solute descriptors inour database are of experimental origin and are based on observed solubility data and Henry’s lawconstants,[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 partiallymiscible) organic solvent.[57]

Calculation of the Abraham model IL-specific equation coefficients is relatively straightforwardand begins with writing a log K and log P equation for each solute–IL solvent pair. For eachequation the measured log K and log P values, as well as the five solute descriptors that appear onthe right-hand side of Equations (1) and (2), are known. This leaves only the six unknownequation coefficients that must be calculated. The resulting set of log K equations are solved


Table3.

Logarithm

ofgas-to-anh

ydrous

ILpartition

coefficient,log

K,andlogarithm

ofwater-to-anhydrou

sILpartition

coefficient,log

P,fororganicsolutesdissolvedin

([AllM

Im]+[N(CN) 2]–)at

298K.

Solute

ES

AB

LV

logK

logP

Pentane

0.000

0.000

0.000

0.000

2.162

0.8131

0.249

1.949

Hexane

0.000

0.000

0.000

0.000

2.668

0.9540

0.501

2.321

3-Methylpentane

0.000

0.000

0.000

0.000

2.581

0.9540

0.487

2.327

2,2-Dimethylbutane

0.000

0.000

0.000

0.000

2.352

0.9540

0.294

2.134

Heptane

0.000

0.000

0.000

0.000

3.173

1.0949

0.772

2.732

Octane

0.000

0.000

0.000

0.000

3.677

1.2358

1.041

3.151

2,2,4-Trimethylpentane

0.000

0.000

0.000

0.000

3.106

1.2358

0.664

2.784

Non

ane

0.000

0.000

0.000

0.000

4.182

1.3767

1.315

3.465

Decane

0.000

0.000

0.000

0.000

4.686

1.5176

1.600

3.920

Cyclop

entane

0.263

0.100

0.000

0.000

2.477

0.7045

0.845

1.725

Cycloh

exane

0.305

0.100

0.000

0.000

2.964

0.8454

1.105

2.005

Methylcyclohexane

0.244

0.060

0.000

0.000

3.319

0.9863

1.198

2.448

Cycloh

eptane

0.350

0.100

0.000

0.000

3.704

0.9863

1.875

2.455

Cyclooctane

0.413

0.100

0.000

0.000

4.329

1.1272

2.011

2.781

1-Pentene

0.093

0.080

0.000

0.070

2.047

0.7701

0.581

1.811

1-Hexene

0.078

0.080

0.000

0.070

2.572

0.9110

0.862

2.022

Cycloh

exene

0.395

0.280

0.000

0.090

2.952

0.8204

1.576

1.846

1-Heptene

0.092

0.080

0.000

0.070

3.063

1.0519

1.109

2.329

1-Octene

0.094

0.080

0.000

0.070

3.568

1.1928

1.371

2.781

1-Decene

0.093

0.080

0.000

0.070

4.554

1.4746

1.868

3.508

1-Pentyne

0.172

0.230

0.120

0.120

2.010

0.7271

1.471

1.481

1-Hexyne

0.166

0.220

0.100

0.120

2.510

0.8680

1.741

1.951

1-Heptyne

0.160

0.230

0.120

0.100

3.000

1.0089

1.985

2.425

1-Octyne

0.155

0.220

0.090

0.100

3.521

1.1498

2.230

2.750

Benzene

0.610

0.520

0.000

0.140

2.786

0.7164

2.425

1.795

Toluene

0.601

0.520

0.000

0.140

3.325

0.8573

2.703

2.053

Ethylbenzene

0.613

0.510

0.000

0.150

3.778

0.9982

2.889

2.309

o-Xylene

0.663

0.560

0.000

0.160

3.939

0.9982

3.169

2.509

m-Xylene

0.623

0.520

0.000

0.160

3.839

0.9982

2.963

2.353

p-Xylene

0.613

0.520

0.000

0.160

3.839

0.9982

2.973

2.383

Prop

ylbenzene

0.604

0.500

0.000

0.150

4.230

1.1391

3.058

2.668

Isop

ropylbenzene

0.602

0.490

0.000

0.160

4.084

1.1391

2.963

2.523

Styrene

0.849

0.650

0.000

0.160

3.908

0.9550

3.434

2.484

α-Methylstyrene

0.851

0.640

0.000

0.190

4.290

1.0960

3.608

2.648

Methano

l0.278

0.440

0.430

0.470

0.970

0.3082

3.059

−0.681

Ethano

l0.246

0.420

0.370

0.480

1.485

0.4491

3.094

−0.576

1-Prop

anol

0.236

0.420

0.370

0.480

2.031

0.5900

3.362

−0.198

2-Prop

anol

0.212

0.360

0.330

0.560

1.764

0.5900

2.996

−0.484

1-Bu

tano

l0.224

0.420

0.370

0.480

2.601

0.7309

3.650

0.190

(Con

tinued)

10 B. JIANG ET AL.

Table3.

(Con

tinued).

Solute

ES

AB

LV

logK

logP

2-Bu

tano

l0.217

0.360

0.330

0.560

2.338

0.7309

3.254

−0.136

2-Methyl-1-propano

l0.217

0.390

0.370

0.480

2.413

0.7309

3.456

0.156

tert-Butanol

0.180

0.300

0.310

0.600

1.963

0.7309

2.897

−0.383

1-Pentanol

0.219

0.420

0.370

0.480

3.106

0.8718

3.921

0.571

Thioph

ene

0.687

0.570

0.000

0.150

2.819

0.6411

2.746

1.706

Tetrahydrofuran

0.289

0.520

0.000

0.480

2.636

0.6223

2.343

−0.207

1,4-Dioxane

0.329

0.750

0.000

0.640

2.892

0.6810

3.187

−0.523

Methyltert-bu

tyle

ther

0.024

0.220

0.000

0.550

2.372

0.8718

1.408

−0.212

Ethyltert-bu

tyle

ther

−0.020

0.180

0.000

0.590

2.699

1.0127

1.213

−0.057

Methyltert-am

ylether

0.050

0.210

0.000

0.600

2.916

1.0127

1.675

0.205

Diethylether

0.041

0.250

0.000

0.450

2.015

0.7309

1.132

−0.038

Dipropyle

ther

0.008

0.250

0.000

0.450

2.954

1.0127

1.426

0.536

Diisop

ropyle

ther

−0.063

0.170

0.000

0.570

2.501

1.0127

1.077

0.027

Dibutylether

0.000

0.250

0.000

0.450

3.924

1.2945

1.909

1.219

Aceton

e0.179

0.700

0.040

0.490

1.696

0.5470

2.450

−0.340

2-Pentanon

e0.143

0.680

0.000

0.510

2.755

0.8288

2.812

0.232

3-Pentanon

e0.154

0.660

0.000

0.510

2.811

0.8288

2.786

0.286

Methylacetate

0.142

0.640

0.000

0.450

1.911

0.6057

2.249

−0.051

Ethylacetate

0.106

0.620

0.000

0.450

2.314

0.7466

2.341

0.181

Methylp

ropano

ate

0.128

0.600

0.000

0.450

2.431

0.7470

2.417

0.267

Methylb

utanoate

0.106

0.600

0.000

0.450

2.943

0.8880

2.604

0.524

Butanal

0.187

0.650

0.000

0.450

2.270

0.6880

2.452

0.122

Aceton

itrile

0.237

0.900

0.070

0.320

1.739

0.4042

2.996

0.146

Pyrid

ine

0.631

0.840

0.000

0.520

3.022

0.6750

3.463

0.023

1-Nitrop

ropane

0.242

0.950

0.000

0.310

2.894

0.7055

3.587

1.137

Water

0.000

0.600

0.590

0.460

0.245

0.1673

3.938

−0.752


Table4.

Logarithm

ofgas-to-anh

ydrous

ILpartition

coefficient,log

K,andlogarithm

ofwater-to-anhydrou

sIL

partition

coefficient,log


([AllM

Im]+[Tf 2N]–)at

298K.

Solute

ES

AB

LV

logK

logP

Hexane

0.000

0.000

0.000

0.000

2.668

0.9540

1.266

3.086

3-Methylpentane

0.000

0.000

0.000

0.000

2.581

0.9540

1.255

3.095

2,2-Dimethylbutane

0.000

0.000

0.000

0.000

2.352

0.9540

1.086

2.926

Heptane

0.000

0.000

0.000

0.000

3.173

1.0949

1.601

3.561

Octane

0.000

0.000

0.000

0.000

3.677

1.2358

1.921

4.031


0.000

0.000

0.000

0.000

3.106

1.2358

1.595

3.715

Non

ane

0.000

0.000

0.000

0.000

4.182

1.3767

2.245

4.395

Decane

0.000

0.000

0.000

0.000

4.686

1.5176

2.554

4.874

Cyclop

entane

0.263

0.100

0.000

0.000

2.477

0.7045

1.360

2.240

Cycloh

exane

0.305

0.100

0.000

0.000

2.964

0.8454

1.702

2.602

Methylcyclohexane

0.244

0.060

0.000

0.000

3.319

0.9863

1.873

3.123

Cycloh

eptane

0.350

0.100

0.000

0.000

3.704

0.9863

2.199

2.779

Cyclooctane

0.413

0.100

0.000

0.000

4.329

1.1272

2.635

3.405

1-Pentene

0.093

0.080

0.000

0.070

2.047

0.7701

1.180

2.410

1-Hexene

0.078

0.080

0.000

0.070

2.572

0.9110

1.509

2.669

Cycloh

exene

0.395

0.280

0.000

0.090

2.952

0.8204

2.029

2.299

1-Heptene

0.092

0.080

0.000

0.070

3.063

1.0519

1.830

3.050

1-Octene

0.094

0.080

0.000

0.070

3.568

1.1928

2.169

3.579

1-Decene

0.093

0.080

0.000

0.070

4.554

1.4746

2.785

4.425

1-Pentyne

0.172

0.230

0.120

0.120

2.010

0.7271

1.828

1.838

1-Hexyne

0.166

0.220

0.100

0.120

2.510

0.8680

2.167

2.377

1-Heptyne

0.160

0.230

0.120

0.100

3.000

1.0089

2.493

2.933

1-Octyne

0.155

0.220

0.090

0.100

3.521

1.1498

2.820

3.340

Benzene

0.610

0.520

0.000

0.140

2.786

0.7164

2.833

2.203

Toluene

0.601

0.520

0.000

0.140

3.325

0.8573

3.186

2.536

Ethylbenzene

0.613

0.510

0.000

0.150

3.778

0.9982

3.445

2.865

o-Xylene

0.663

0.560

0.000

0.160

3.939

0.9982

3.686

3.026

m-Xylene

0.623

0.520

0.000

0.160

3.839

0.9982

3.523

2.913

p-Xylene

0.613

0.520

0.000

0.160

3.839

0.9982

3.514

2.924

Prop

ylbenzene

0.604

0.500

0.000

0.150

4.230

1.1391

3.709

3.319

Isop

ropylbenzene

0.602

0.490

0.000

0.160

4.084

1.1391

3.600

3.160

Styrene

0.849

0.650

0.000

0.160

3.908

0.9550

3.914

2.964

α-Methylstyrene

0.851

0.640

0.000

0.190

4.290

1.0960

4.102

3.142

Methano

l0.278

0.440

0.430

0.470

0.970

0.3082

2.563

−1.177

Ethano

l0.246

0.420

0.370

0.480

1.485

0.4491

2.773

−0.897

1-Prop

anol

0.236

0.420

0.370

0.480

2.031

0.5900

3.114

−0.446

2-Prop

anol

0.212

0.360

0.330

0.560

1.764

0.5900

2.835

−0.645

1-Bu

tano

l0.224

0.420

0.370

0.480

2.601

0.7309

3.474

0.014

2-Bu

tano

l0.217

0.360

0.330

0.560

2.338

0.7309

3.141

−0.249

(Con

tinued)

12 B. JIANG ET AL.

Table4.

(Con

tinued).

Solute

ES

AB

LV

logK

logP

2-Methyl-1-propano

l0.2170

0.390

0.370

0.480

2.413

0.7309

3.293

−0.007

tert-Butanol

0.180

0.300

0.310

0.600

1.963

0.7309

2.865

−0.415

1-Pentanol

0.219

0.420

0.370

0.480

3.106

0.8718

3.822

0.472

Thioph

ene

0.687

0.570

0.000

0.150

2.819

0.6411

2.958

1.918

Tetrahydrofuran

0.289

0.520

0.000

0.480

2.636

0.6223

2.808

0.258

1,4-Dioxane

0.329

0.750

0.000

0.640

2.892

0.6810

3.575

−0.135

Methyltert-bu

tyle

ther

0.024

0.220

0.000

0.550

2.372

0.8718

2.097

0.477

Ethyltert-bu

tyle

ther

−0.020

0.180

0.000

0.590

2.699

1.0127

2.013

0.743

Methyltert-am

ylether

0.050

0.210

0.000

0.600

2.916

1.0127

2.427

0.957

Diethylether

0.041

0.250

0.000

0.450

2.015

0.7309

1.750

0.580

Dipropyle

ther

0.008

0.250

0.000

0.450

2.954

1.0127

2.196

1.306

Diisop

ropyle

ther

−0.063

0.170

0.000

0.570

2.501

1.0127

1.917

0.867

Dibutylether

0.000

0.250

0.000

0.450

3.924

1.2945

2.813

2.123

Aceton

e0.179

0.700

0.040

0.490

1.696

0.5470

2.913

0.123

2-Pentanon

e0.143

0.680

0.000

0.510

2.755

0.8288

3.446

0.866

3-Pentanon

e0.154

0.660

0.000

0.510

2.811

0.8288

3.421

0.921

Methylacetate

0.142

0.640

0.000

0.450

1.911

0.6057

2.751

0.451

Ethylacetate

0.106

0.620

0.000

0.450

2.314

0.7466

2.975

0.815

Methylp

ropano

ate

0.128

0.600

0.000

0.450

2.431

0.7470

3.021

0.871

Methylb

utanoate

0.106

0.600

0.000

0.450

2.943

0.8880

3.278

1.198

Butanal

0.187

0.650

0.000

0.450

2.270

0.6880

2.948

0.618

Aceton

itrile

0.237

0.900

0.070

0.320

1.739

0.4042

3.265

0.415

Pyrid

ine

0.631

0.840

0.000

0.520

3.022

0.6750

3.804

0.364

1-Nitrop

ropane

0.242

0.950

0.000

0.310

2.894

0.7055

3.987

1.537

Water

0.000

0.600

0.590

0.460

0.245

0.1673

2.731

−1.959


Table5.

Logarithm

ofgas-to-anh

ydrous

ILpartition

coefficient,log

K,andlogarithm

ofwater-to-anhydrou

sILpartition

coefficient,log

P,foro

rganicsolutesdissolvedin([B

3EP]

+[E2PO4]–)at2

98K.

Solute

ES

AB

LV

logK

logP

Pentane

0.000

0.000

0.000

0.000

2.162

0.8131

1.475

3.175

Hexane

0.000

0.000

0.000

0.000

2.668

0.9540

1.929

3.749

3-Methylpentane

0.000

0.000

0.000

0.000

2.581

0.9540

1.864

3.704

2,2-Dimethylbutane

0.000

0.000

0.000

0.000

2.352

0.9540

1.617

3.457

Heptane

0.000

0.000

0.000

0.000

3.173

1.0949

2.357

4.317

Octane

0.000

0.000

0.000

0.000

3.677

1.2358

2.794

4.904


0.000

0.000

0.000

0.000

3.106

1.2358

2.287

4.407

Non

ane

0.000

0.000

0.000

0.000

4.182

1.3767

3.206

5.356

Decane

0.000

0.000

0.000

0.000

4.686

1.5176

3.619

5.939

Cyclop

entane

0.263

0.100

0.000

0.000

2.477

0.7045

1.888

2.768

Cycloh

exane

0.305

0.100

0.000

0.000

2.964

0.8454

2.312

3.212

Methylcyclohexane

0.244

0.060

0.000

0.000

3.319

0.9863

2.557

3.807

Cycloh

eptane

0.350

0.100

0.000

0.000

3.704

0.9863

2.899

3.479

Cyclooctane

0.413

0.100

0.000

0.000

4.329

1.1272

3.422

4.192

1-Pentene

0.093

0.080

0.000

0.070

2.047

0.7701

1.532

2.762

1-Hexene

0.078

0.080

0.000

0.070

2.572

0.9110

1.991

3.151

Cycloh

exene

0.395

0.280

0.000

0.090

2.952

0.8204

2.465

2.735

1-Heptene

0.092

0.080

0.000

0.070

3.063

1.0519

2.407

3.627

1-Octene

0.094

0.080

0.000

0.070

3.568

1.1928

2.828

4.238

1-Decene

0.093

0.080

0.000

0.070

4.554

1.4746

3.646

5.286

1-Pentyne

0.172

0.230

0.120

0.120

2.010

0.7271

2.254

2.264

1-Hexyne

0.166

0.220

0.100

0.120

2.510

0.8680

2.697

2.907

1-Heptyne

0.160

0.230

0.120

0.100

3.000

1.0089

3.108

3.548

1-Octyne

0.155

0.220

0.090

0.100

3.521

1.1498

3.545

4.065

Benzene

0.610

0.520

0.000

0.140

2.786

0.7164

2.732

2.102

Toluene

0.601

0.520

0.000

0.140

3.325

0.8573

3.115

2.465

Ethylbenzene

0.613

0.510

0.000

0.150

3.778

0.9982

3.462

2.882

o-Xylene

0.663

0.560

0.000

0.160

3.939

0.9982

3.618

2.958

m-Xylene

0.623

0.520

0.000

0.160

3.839

0.9982

3.483

2.873

p-Xylene

0.613

0.520

0.000

0.160

3.839

0.9982

3.488

2.898

Styrene

0.849

0.650

0.000

0.160

3.908

0.9550

3.892

2.942

Thioph

ene

0.687

0.570

0.000

0.150

2.819

0.6411

3.024

1.984

Tetrahydrofuran

0.289

0.520

0.000

0.480

2.636

0.6223

2.471

−0.079

1,4-Dioxane

0.329

0.750

0.000

0.640

2.892

0.6810

3.039

−0.671

Methyltert-bu

tyle

ther

0.024

0.220

0.000

0.550

2.372

0.8718

1.984

0.364

Ethyltert-bu

tyle

ther

−0.020

0.180

0.000

0.590

2.699

1.0127

2.115

0.845

Methyltert-am

ylether

0.050

0.210

0.000

0.600

2.916

1.0127

2.455

0.985

Diethylether

0.041

0.250

0.000

0.450

2.015

0.7309

1.678

0.508

Dipropyle

ther

0.008

0.250

0.000

0.450

2.954

1.0127

2.432

1.542

Diisop

ropyle

ther

−0.063

0.170

0.000

0.570

2.501

1.0127

2.013

0.963

(Con

tinued)

14 B. JIANG ET AL.

Table5.

(Con

tinued).

Solute

ES

AB

LV

logK

logP

Dibutylether

0.000

0.250

0.000

0.450

3.924

1.2945

3.239

2.549

Aceton

e0.179

0.700

0.040

0.490

1.696

0.5470

2.380

−0.410

2-Pentanon

e0.143

0.680

0.000

0.510

2.755

0.8288

3.097

0.517

3-Pentanon

e0.154

0.660

0.000

0.510

2.811

0.8288

3.092

0.592

2-Hexanon

e0.136

0.680

0.000

0.510

3.286

0.9697

3.530

1.120

3-Hexanon

e0.136

0.660

0.000

0.510

3.271

0.9697

3.419

1.149

Pyrid

ine

0.631

0.840

0.000

0.520

3.022

0.6750

3.618

0.178

1-Nitrop

ropane

0.242

0.950

0.000

0.310

2.894

0.7055

3.987

1.537

Water

0.000

0.600

0.590

0.460

0.245

0.1673

4.344

−0.346


Table6.

Logarithm

ofgas-to-anh

ydrous

ILpartition

coefficient,log

K,andlogarithm

ofwater-to-anhydrou

sIL

partition

coefficient,log


([OE 3Am

]+[Tf 2N]–)at

298K.

Solute

ES

AB

LV

logK

logP

Pentane

0.000

0.000

0.000

0.000

2.162

0.8131

1.300

3.000

Hexane

0.000

0.000

0.000

0.000

2.668

0.9540

1.748

3.568

3-Methylpentane

0.000

0.000

0.000

0.000

2.581

0.9540

1.682

3.522

2,2-Dimethylbutane

0.000

0.000

0.000

0.000

2.352

0.9540

1.438

3.278

Heptane

0.000

0.000

0.000

0.000

3.173

1.0949

2.160

4.120

Octane

0.000

0.000

0.000

0.000

3.677

1.2358

2.558

4.668


0.000

0.000

0.000

0.000

3.106

1.2358

2.126

4.246

Non

ane

0.000

0.000

0.000

0.000

4.182

1.3767

2.960

5.110

Decane

0.000

0.000

0.000

0.000

4.686

1.5176

3.352

5.672

Cyclop

entane

0.263

0.100

0.000

0.000

2.477

0.7045

1.701

2.581

Cycloh

exane

0.305

0.100

0.000

0.000

2.964

0.8454

2.096

2.996

Methylcyclohexane

0.244

0.060

0.000

0.000

3.319

0.9863

2.335

3.585

Cycloh

eptane

0.350

0.100

0.000

0.000

3.704

0.9863

2.649

3.229

Cyclooctane

0.413

0.100

0.000

0.000

4.329

1.1272

3.149

3.919

1-Pentene

0.093

0.080

0.000

0.070

2.047

0.7701

1.437

2.667

1-Hexene

0.078

0.080

0.000

0.070

2.572

0.9110

1.874

3.034

Cycloh

exene

0.395

0.280

0.000

0.090

2.952

0.8204

2.329

2.599

1-Heptene

0.092

0.080

0.000

0.070

3.063

1.0519

2.275

3.495

1-Octene

0.094

0.080

0.000

0.070

3.568

1.1928

2.673

4.083

1-Decene

0.093

0.080

0.000

0.070

4.554

1.4746

3.459

5.099

1-Pentyne

0.172

0.230

0.120

0.120

2.010

0.7271

1.966

1.976

1-Hexyne

0.166

0.220

0.100

0.120

2.510

0.8680

2.370

2.580

1-Heptyne

0.160

0.230

0.120

0.100

3.000

1.0089

2.777

3.217

1-Octyne

0.155

0.220

0.090

0.100

3.521

1.1498

3.170

3.690

Benzene

0.610

0.520

0.000

0.140

2.786

0.7164

2.944

2.314

Toluene

0.601

0.520

0.000

0.140

3.325

0.8573

3.357

2.707

Ethylbenzene

0.613

0.510

0.000

0.150

3.778

0.9982

3.677

3.097

o-Xylene

0.663

0.560

0.000

0.160

3.939

0.9982

3.900

3.240

m-Xylene

0.623

0.520

0.000

0.160

3.839

0.9982

3.765

3.155

p-Xylene

0.613

0.520

0.000

0.160

3.839

0.9982

3.744

3.154

Styrene

0.849

0.650

0.000

0.160

3.908

0.9550

4.114

3.164

α-Methylstyrene

0.851

0.640

0.000

0.190

4.290

1.0960

4.359

3.399

Methano

l0.278

0.440

0.430

0.470

0.970

0.3082

2.372

−1.368

Ethano

l0.246

0.420

0.370

0.480

1.485

0.4491

2.620

−1.050

1-Prop

anol

0.236

0.420

0.370

0.480

2.031

0.5900

3.019

−0.541

2-Prop

anol

0.212

0.360

0.330

0.560

1.764

0.5900

2.730

−0.750

1-Bu

tano

l0.224

0.420

0.370

0.480

2.601

0.7309

3.450

−0.010

2-Bu

tano

l0.217

0.360

0.330

0.560

2.338

0.7309

3.108

−0.282

2-Methyl-1-propano

l0.2170

0.390

0.370

0.480

2.413

0.7309

3.249

−0.051

(Con

tinued)

16 B. JIANG ET AL.

Table6.

(Con

tinued).

Solute

ES

AB

LV

logK

logP

tert-Butanol

0.180

0.300

0.310

0.600

1.963

0.7309

2.804

−0.476

1-Pentanol

0.219

0.420

0.370

0.480

3.106

0.8718

3.869

0.519

Thioph

ene

0.687

0.570

0.000

0.150

2.819

0.6411

3.039

1.999

Tetrahydrofuran

0.289

0.520

0.000

0.480

2.636

0.6223

2.767

0.217

1,4-Dioxane

0.329

0.750

0.000

0.640

2.892

0.6810

3.378

−0.332

Methyltert-bu

tyle

ther

0.024

0.220

0.000

0.550

2.372

0.8718

2.140

0.520

Ethyltert-bu

tyle

ther

−0.020

0.180

0.000

0.590

2.699

1.0127

2.126

0.856

Methyltert-am

ylether

0.050

0.210

0.000

0.600

2.916

1.0127

2.545

1.075

Diethylether

0.041

0.250

0.000

0.450

2.015

0.7309

1.783

0.613

Dipropyle

ther

0.008

0.250

0.000

0.450

2.954

1.0127

2.423

1.533

Diisop

ropyle

ther

−0.063

0.170

0.000

0.570

2.501

1.0127

2.048

0.998

Dibutylether

0.000

0.250

0.000

0.450

3.924

1.2945

3.177

2.487

Aceton

e0.179

0.700

0.040

0.490

1.696

0.5470

2.702

−0.088

2-Pentanon

e0.143

0.680

0.000

0.510

2.755

0.8288

3.404

0.824

3-Pentanon

e0.154

0.660

0.000

0.510

2.811

0.8288

3.403

0.903

Methylacetate

0.142

0.640

0.000

0.450

1.911

0.6057

2.554

0.254

Ethylacetate

0.106

0.620

0.000

0.450

2.314

0.7466

2.861

0.701

Methylp

ropano

ate

0.128

0.600

0.000

0.450

2.431

0.7470

2.923

0.773

Methylb

utanoate

0.106

0.600

0.000

0.450

2.943

0.8880

3.265

1.185

Butanal

0.187

0.650

0.000

0.450

2.270

0.6880

2.885

0.555

Aceton

itrile

0.237

0.900

0.070

0.320

1.739

0.4042

3.006

0.156

Pyrid

ine

0.631

0.840

0.000

0.520

3.022

0.6750

3.730

0.290

1-Nitrop

ropane

0.242

0.950

0.000

0.310

2.894

0.7055

3.882

1.432

Water

0.000

0.600

0.590

0.460

0.245

0.1673

2.456

−2.234


Table7.

Logarithm

ofgas-to-anh

ydrous

ILpartition

coefficient,log

K,andlogarithm

ofwater-to-anhydrou

sILpartition

coefficient,log


([BMMorp]

+[C(CN) 3]–)a

t298K.

Solute

ES

AB

LV

logK

logP

Pentane

0.000

0.000

0.000

0.000

2.162

0.8131

0.519

2.219

Hexane

0.000

0.000

0.000

0.000

2.668

0.9540

0.895

2.715

3-Methylpentane

0.000

0.000

0.000

0.000

2.581

0.9540

0.834

2.674

2,2-Dimethylbutane

0.000

0.000

0.000

0.000

2.352

0.9540

0.551

2.391

Heptane

0.000

0.000

0.000

0.000

3.173

1.0949

1.254

3.214

Octane

0.000

0.000

0.000

0.000

3.677

1.2358

1.574

3.684


0.000

0.000

0.000

0.000

3.106

1.2358

1.119

3.239

Non

ane

0.000

0.000

0.000

0.000

4.182

1.3767

1.909

4.059

Decane

0.000

0.000

0.000

0.000

4.686

1.5176

2.187

4.507

Cyclop

entane

0.263

0.100

0.000

0.000

2.477

0.7045

1.191

2.071

Cycloh

exane

0.305

0.100

0.000

0.000

2.964

0.8454

1.502

2.402

Methylcyclohexane

0.244

0.060

0.000

0.000

3.319

0.9863

1.627

2.857

Cycloh

eptane

0.350

0.100

0.000

0.000

3.704

0.9863

2.058

2.638

Cyclooctane

0.413

0.100

0.000

0.000

4.329

1.1272

2.520

3.290

1-Hexene

0.078

0.080

0.000

0.070

2.572

0.9110

1.261

2.421

Cycloh

exene

0.395

0.280

0.000

0.090

2.952

0.8204

1.958

2.228

1-Heptene

0.092

0.080

0.000

0.070

3.063

1.0519

1.578

2.798

1-Octene

0.094

0.080

0.000

0.070

3.568

1.1928

1.893

3.303

1-Decene

0.093

0.080

0.000

0.070

4.554

1.4746

2.513

4.133

1-Pentyne

0.172

0.230

0.120

0.120

2.010

0.7271

1.732

1.742

1-Hexyne

0.166

0.220

0.100

0.120

2.510

0.8680

2.067

2.277

1-Heptyne

0.160

0.230

0.120

0.100

3.000

1.0089

2.379

2.819

1-Octyne

0.155

0.220

0.090

0.100

3.521

1.1498

2.680

3.200

Benzene

0.610

0.520

0.000

0.140

2.786

0.7164

2.777

2.147

Toluene

0.601

0.520

0.000

0.140

3.325

0.8573

3.116

2.466

Ethylbenzene

0.613

0.510

0.000

0.150

3.778

0.9982

3.364

2.784

o-Xylene

0.663

0.560

0.000

0.160

3.939

0.9982

3.634

2.974

m-Xylene

0.623

0.520

0.000

0.160

3.839

0.9982

3.451

2.841

p-Xylene

0.613

0.520

0.000

0.160

3.839

0.9982

3.443

2.853

Styrene

0.849

0.650

0.000

0.160

3.908

0.9550

3.890

2.940

α-Methylstyrene

0.851

0.640

0.000

0.190

4.290

1.0960

4.065

3.105

Methano

l0.278

0.440

0.430

0.470

0.970

0.3082

2.868

−0.872

Ethano

l0.246

0.420

0.370

0.480

1.485

0.4491

2.994

−0.676

1-Prop

anol

0.236

0.420

0.370

0.480

2.031

0.5900

3.318

−0.242

2-Prop

anol

0.212

0.360

0.330

0.560

1.764

0.5900

2.972

−0.508

1-Bu

tano

l0.224

0.420

0.370

0.480

2.601

0.7309

3.680

0.220

2-Bu

tano

l0.217

0.360

0.330

0.560

2.338

0.7309

3.294

−0.096

2-Methyl-1-propano

l0.2170

0.390

0.370

0.480

2.413

0.7309

3.473

0.173

tert-Butanol

0.180

0.300

0.310

0.600

1.963

0.7309

2.923

−0.357

(Con

tinued)

18 B. JIANG ET AL.

Table7.

(Con

tinued).

Solute

ES

AB

LV

logK

logP

Thioph

ene

0.687

0.570

0.000

0.150

2.819

0.6411

3.043

2.003

Tetrahydrofuran

0.289

0.520

0.000

0.480

2.636

0.6223

2.684

0.134

1,4-Dioxane

0.329

0.750

0.000

0.640

2.892

0.6810

3.537

−0.173

Methyltert-bu

tyle

ther

0.024

0.220

0.000

0.550

2.372

0.8718

1.778

0.158

Ethyltert-bu

tyle

ther

−0.020

0.180

0.000

0.590

2.699

1.0127

1.563

0.293

Methyltert-am

ylether

0.050

0.210

0.000

0.600

2.916

1.0127

2.100

0.630

Diethylether

0.041

0.250

0.000

0.450

2.015

0.7309

1.456

0.286

Dipropyle

ther

0.008

0.250

0.000

0.450

2.954

1.0127

1.882

0.992

Diisop

ropyle

ther

−0.063

0.170

0.000

0.570

2.501

1.0127

1.475

0.425

Dibutylether

0.000

0.250

0.000

0.450

3.924

1.2945

2.464

1.774

Aceton

e0.179

0.700

0.040

0.490

1.696

0.5470

2.711

−0.079

2-Pentanon

e0.143

0.680

0.000

0.510

2.755

0.8288

3.226

0.646

3-Pentanon

e0.154

0.660

0.000

0.510

2.811

0.8288

3.213

0.713

Methylacetate

0.142

0.640

0.000

0.450

1.911

0.6057

2.536

0.236

Ethylacetate

0.106

0.620

0.000

0.450

2.314

0.7466

2.696

0.536

Methylp

ropano

ate

0.128

0.600

0.000

0.450

2.431

0.7470

2.799

0.649

Methylb

utanoate

0.106

0.600

0.000

0.450

2.943

0.8880

3.037

0.957

Butanal

0.187

0.650

0.000

0.450

2.270

0.6880

2.818

0.488

Aceton

itrile

0.237

0.900

0.070

0.320

1.739

0.4042

3.193

0.343

Pyrid

ine

0.631

0.840

0.000

0.520

3.022

0.6750

3.755

0.315

1-Nitrop

ropane

0.242

0.950

0.000

0.310

2.894

0.7055

3.931

1.481

Water

0.000

0.600

0.590

0.460

0.245

0.1673

3.479

−1.211


simultaneously to give the numerical values of ck,il, ek,il, sk,il, ak,il, bk,il and lk,il that best describe theobserved gas-to-IL partition coefficient data. The equation coefficients for the set of log Pequations 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 wereobtained by regression analysis using the IBM SPSS Statistics Package, Version 22. The statisticalinformation 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 fromthe IL-specific equation coefficients (e.g. ccation = cIL – canion; ecation = eIL – eanion, etc.). Thecomputational 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 andcontain partition coefficients for 65 and 64 organic solutes, respectively. An analysis of the experimentallog P and log K values in Tables 3 and 4 yielded the following four Abraham model IL-specificcorrelations:

For ([AllMIm]+[N(CN)2]–):

log P 298Kð Þ¼ �0:202 0:087ð Þ þ 0:360 0:083ð ÞEþ 0:780 0:099ð ÞSþ 0:790 0:122ð ÞA� 4:475 0:095ð ÞBþ 2:621 0:076ð ÞVwith N ¼ 65; SD ¼ 0:102; R2 ¼ 0:994; F ¼ 1890� � (7)

log K 298Kð Þ¼ �0:815 0:060ð Þ þ 0:534 0:076ð ÞEþ 2:719 0:076ð ÞSþ 4:550 0:100ð ÞAþ 0:450 0:079ð ÞBþ 0:514 0:018ð ÞLwith N ¼ 65; SD ¼ 0:084;R2 ¼ 0:993; F ¼ 1706� � (8)

For ([AllMIm]+[Tf2N]–):

log P 298Kð Þ¼ 0:058 0:090ð ÞEþ 0:703 0:096ð ÞS� 1:301 0:115ð ÞA� 4:343 0:103ð ÞBþ 3:159 0:025ð ÞVwith N ¼ 64; SD ¼ 0:112;R2 ¼ 0:998; F ¼ 5328� � (9)

log K 298Kð Þ ¼ �0:420 0:058ð Þþ0:081 0:071ð ÞEþ 2:493 0:072ð ÞSþ 2:369 0:094ð ÞAþ 0:599 0:074ð ÞBþ 0:643 0:017ð ÞLwith N ¼ 64; SD ¼ 0:079;R2 ¼ 0:990; F ¼ 1160� � (10)

The standard errors in each of the calculated equation coefficients are given in parenthesesimmediately after the respective coefficient. An examination of the associated statistical informa-tion reveals that the derived correlations provide a very good mathematical description of solutetransfer 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 to0.998, and large Fisher F-statistical values, F = 1160 to 5328, for Equations (7)–(10). Figures 1 and2 depict a graphical comparison of the experimental log P data vs. back-calculated values based onour 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 Figures3 and 4. There are insufficient experimental data to permit a training set and test set assessment ofthe 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 topredict log P and log K values for additional organic solutes dissolved in ([AllMIm]+[N(CN)2]

–)

20 B. JIANG ET AL.

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 abilitycan 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 foreither IL solvent. From a purely mathematical standpoint it is easier to perform the calculationsusing the correlations for ([AllMIm]+[Tf2N]

–). In developing the ion-specific model, Sprungerand co-workers [38–40] needed a reference point for calculating the numerical values forindividual ions. In an IL solvent the ions come as a cation–anion pair, and to calculate the valuesfor 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]

–).


coefficients in Equations (9) and (10) are not only the IL-specific equation coefficients for theentire ([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]+ cationfrom Equations (7) and (8) as log P and log K equation coefficients for the [N(CN)2]]

– anion areknown: (cp,anion = –0.257; ep,anion = 0.164; sp,anion = 0.446; ap,anion = 2.217; bp,anion = –0.256 andvp,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 dissolvedin ([AllMIm]+[Tf2N]

–).

22 B. JIANG ET AL.

coefficients for the log P and log K correlations. The average [AllMIm]+-specific equationcoefficients 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 andSE = 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 towater-to-IL partition coefficients. The computations are in accord with our earlier observations inthat the best predictions are obtained using the IL-specific Abraham model correlations, which forthese two ILs would be Equations (7)–(10).

We suspect that we can improve on the predictions by recalculating the equation coefficientsfor 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] wouldnearly 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 analysison our entire IL database. The last regression analysis of the entire IL database was done just over2 years ago,[41] and at the time there were 3731 experimental log P values and 3786 experimentallog K values. It is not computationally feasible to perform a complete reanalysis every time that anew cation or anion is added to the database. A complete reanalysis will change most (if not all) ofthe existing values that have been calculated for the 40 cations and 16 anions that were in thedatabase when the values were last updated. It will be difficult for readers to keep track of thelatest set of equation coefficients. We prefer to update values every few years whenever there hasbeen sufficient new experimental values added to the large database to warrant the computationaleffort.

The ([B3EP]+[E2PO4]

–) data set is the smallest of the five IL data sets, and it containsexperimental partition coefficients for only 49 solutes. Preliminary regression analysis of theexperimental data in Table 5 gave an Abraham model log K correlation:

log K 298Kð Þ¼ �0:279 0:074ð Þ � 0:441 0:097ð ÞEþ 1:952 0:104ð ÞSþ 5:698 0:190ð ÞA� 0:382 0:105ð ÞBþ 0:823 0:022ð ÞLwith N ¼ 49; SD ¼ 0:089;R2 ¼ 0:984; F ¼ 543:2� � (11)

which had a negative numerical value for the bk,il coefficient. A negative bk,il coefficient is notrealistic 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 2.864Average 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 0.569Average for [AllMIm]+ log K −0.432 0.135 2.368 2.324 0.624 0.606


the gas phase. We removed the bk,il·B from Equation (11), and re-analysed all of the experimentaldata in Table 5. The final Abraham model correlations,

log P 298Kð Þ ¼ 0:120 0:127ð Þ � 0:242 0:137ð ÞEþ 0:309 0:153ð ÞSþ 1:899 0:269ð ÞA� 5:345 0:150ð ÞBþ 3:723 0:110ð ÞVwith N ¼ 49; SD ¼ 0:128;R2 ¼ 0:994; F ¼ 1389� � (12)

log K 298Kð Þ ¼ �0:357 0:080ð Þ � 0:224 0:086ð ÞEþ 1:663 0:073ð ÞSþ 5:859 0:209ð ÞAþ 0:844 0:025ð ÞLwith N ¼ 49; SD ¼ 0:102;R2 ¼ 0:980; F ¼ 527:8� � (13)

describe the partitioning behaviour of 49 organic solutes into ([B3EP]+[E2PO4]

–) to within astandard deviation of 0.128 log units. As an informational note, there was very little loss indescriptive ability by removing the bk,il·B term from the log K equation. The standard deviationwas SD = 0.089 log units with the term included in the correlation vs. SD = 0.102 log unitswithout 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 fromthe respective coefficients in Equations (12) and (13) results in the following set of coefficients forthe [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 fashionto yield the following two sets of Abraham model IL-specific correlations:

For ([OE3Am]+[Tf2N]–):

log P 298Kð Þ ¼ �0:044 0:096ð Þ þ 0:111 0:091ð ÞEþ 0:398 0:108ð ÞS� 1:298 0:133ð ÞA� 4:815 0:103ð ÞBþ 3:667 0:085ð ÞVwith N ¼ 63; SD ¼ 0:110;R2 ¼ 0:996; F ¼ 3022� � (14)

log K 298Kð Þ ¼ �0:378 0:053ð Þ � 0:074 0:066ð ÞEþ 2:088 0:066ð ÞSþ 2:368 0:087ð ÞAþ 0:166 0:068ð ÞBþ 0:792 0:016ð ÞLwith N ¼ 63; SD ¼ 0:073;R2 ¼ 0:990; F ¼ 1075� � (15)

For ([BMMorp]+[C(CN)3]–):

log P 298Kð Þ ¼ �0:318 0:088ð Þ þ 0:374 0:093ð ÞEþ 0:951 0:104ð ÞS� 4:484 0:101ð ÞBþ 3:122 0:076ð ÞVwith N ¼ 61; SD ¼ 0:114;R2 ¼ 0:994; F ¼ 2243� � (16)

log K 298Kð Þ ¼ �0:774 0:067ð Þ þ 0:371 0:078ð ÞEþ 2:762 0:078ð ÞSþ 3:707 0:109ð ÞAþ 0:452 0:080ð ÞBþ 0:643 0:020ð ÞLwith N ¼ 61; SD ¼ 0:086;R2 ¼ 0:991; F ¼ 1269� � (17)

As an informational note, the ap,il·A term made a negligible contribution to the overall log Pcorrelation. The calculated ap,il coefficient was very small (0.021) and the standard error in thecoefficient 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 forsolute transfer into both ([OE3Am]+[Tf2N]

–) and ([BMMorp]+[C(CN)3]–). There is insufficient

24 B. JIANG ET AL.

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 valuesfor 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 thatare 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 moreinvolved and requires knowledge of the equation coefficients for the [C(CN)3]

– anion, which areavailable in the published tabulations in the paper by Stephens and co-workers.[41] The equationcoefficients 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-specificequation coefficients from the respective coefficients in Equations (16) and (17) results in thefollowing 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 calculatedcation-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 havestudied in the present communication, we can build log K and log P Abraham model predictivecorrelations for an additional 19 different IL solvents. This increases the Abraham model’spredictive capability by an additional 76 different IL solvents.

4. Conclusion

The Abraham model has been shown to provide very good mathematical descriptions of thewater-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 coefficientdata to within standard deviations from SD = 0.073 log units to SD = 0.128 log units. As part ofthe present communication, cation-specific equation coefficients have been calculated for[AllMIm]+, [OE3Am]+, [B3EP]

+ and [BMMorp]+. For each of the four cations that we havestudied in the present communication, we can build log K and log P Abraham model predictivecorrelations for an additional 19 different IL solvents. This increases the Abraham model’spredictive 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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