J . Phys. Chem. 1988, 92, 3613-3622
3613
Linear Solvation Energy Relationships. Standard Molar Gibbs Free Energies and Enthalpies of Transfer of Ions from Water into Nonaqueous Solvents Y. Marcus,*,+M. J. Kamlet,t and R. W. Tafts Department of Inorganic & Analytical Chemistry, The Hebrew University of Jerusalem, 91 904 Jerusalem, Israel, Naval Surface Weapons Center, White Oak Laboratory, Silver Springs, Maryland 2091 0, and Department of Chemistry, University of California at Irvine, Irvine, California 9271 7 (Received: July 28, 1987; In Final Form: January 2, 1988)
Data from the literature on the standard molar Gibbs free energies and enthalpies of transfer of ions from water into nonaqueous solvents have been subjected to multiparameter correlations with solvatochromic and other properties of the solvents and with suitable properties of the ions. Three parameters, a*,a,and p for small univalent or divalent cations and a*,a,and V/100 for anions, are adequate for expressing the dependence of AtrGo or AtrHoon the properties of the solvents. Four further (normalized) properties, z , O , l / r ,u, and lOOu, are required for the dependence of the properties of the ions. The first two of these occur only in the combinations zz X O.l/r and z X O.l/r for small cations (for the anions z is unimportant, since only univalent ones are considered). For the large, hydrophobic tetraalkylammoniumcations only two solvent properties, a* and 62/1000(for AuGo) or V/lOO (for A T P ) ,and two ion properties, l / r and R , or lOOu, are required. These dependencies are rationalized in terms of the interactions that take place in water and the nonaqueous solvents.
Introduction One of us has recently coauthored a paper on the relationship of the Gibbs free energies of transfer of ions from water into nonaqueous solvents with certain properties of the solvents and the ions.' The treatment was limited to univalent ions, and the properties of the solvents considered did not include some of their solvatochromic properties,2 which are of extensive use nowadays. Additional standard molar Gibbs free-energy data on the transfer of univalent ions into further solvents and on the transfer of divalent cations have since become a ~ a i l a b l e . ~Also, a critical compilation of standard molar enthalpies of transfer has been p~blished.~It is, therefore, of interest to extend the previous work to accommodate the additional data and to reinterpret the relationships that are found in terms of the interactions that take place in water on the one hand and in the nonaqueous solvents into which the ions transfer, on the other. The previous work' has shown that the Gibbs free energies of transfer of ions (X) from water (W) to nonaqueous solvents (S) can be described by the following linear solvation energy relationship:
The summation extends over all the products of the A,(j)properties of the ith ion X pertinent to their j-type interactions with the solvents S, and the differences between the Po') properties of the solvents S and those of water W. Of the multitude of solvent properties P ( j ) that may be considered, only four took care of almost all of the variance of the Gibbs free-energy data. These are the propensity of the solvent to accept a hydrogen bond or to donate an electron pair, described by its donor number, DN,596 its propensity to donate a hydrogen bond (for protic solvents) or accept an electron pair, described by its ET value,' the reciprocal of its dielectric constant, l / c , and its cohesive energy density or the square of its solubility parameter, a2. Of these, the donor number, DN, did not play a significant role in explaining the variance of the anion transfer data, as might be expected, but unexpectedly the electron-pair-acceptance index, ET,was required for explaining the variance of the cation-transfer data. The regression was applied in two stages, first for each ion on the properties of the solvents and then for each of the coefficients found in the first stage on the properties of the ions. Since for *To whom correspondence should be addressed at The Hebrew University of Jerusalem. 'Work done partly at the University of California at Irvine. 3 Naval Surface Weapons Center. 8 University of California at Irvine
0022-3654/88/2092-3613$01.50/0
both the Gibbs free energies and the enthalpies the quantities pertain to the transfer from water, the properties of the solvents are the differences of given properties and the corresponding ones for water. As before, it has now been endeavored to describe the extended (but still incomplete) matrix of solvents and ions by means of a multivariable linear regression involving the minimum number of variables, applying statistical criteria of the goodness of fit. These are the multiple correlation coefficient squared, R2,which describes the fraction of the variance explained by the regression, and the Fm,"statistic, for m independent variables and n data, which should be larger than the 95% significance level. In view of the previous work,' the following properties Po') of the solvents have now been examined: the polarity-polarizability index,2 a*, the hydrogen-bond-donation ability,2 a , the hydrogen-bond-acceptance ability,2 fi (which is well correlated with DN6), the normalized reciprocal of the dielectric constant, lo/€, the normalized square of the solubility parameter, d2/1000 (with ) , the normalized molar volume, V/100 expressed in J ~ m - ~and (with Vexpressed in cm3 mol-'). Normalized properties are used, which are approximately in the range from 0 to 1, so that the relative contributions of the various variables can be more readily compared. It is realized that six variables are, indeed, not required for an adequate description of the variance, but a selection among them was left for the statistical criteria mentioned above. The coefficients A,(j)themselves depend on various properties of the ions, in a linear solvation energy relation of the form A,(j) = CAijPi i
Of the properties of the ions Pi examined, the charge, z , becomes of larger significance than before, since divalent cations were now included and not only univalent cations and anions. The electrical field strength of the ions was expressed in terms of the charge and of the reciprocal of the crystal ionic radius (in nanometers), l / r . The size of the ion was expressed as the volume occupied (1) Glikberg, S.; Marcus, Y. J . Solution Chem. 1983, 12, 255. (2) Kamlet, M. J.; Abboud, J.-L. M.; Abraham, M. H.; Taft, R. W. J . Org. Chem. 1983, 48, 2877. (3).Marcus, Y. Pure Appl. Chem. 1983, 55, 977, and additional reports listed In Table I. (4) Marcus, Y. Pure Appl. Chem. 1985, 57, 1103, and additional reports
listed in Table 11. ( 5 ) Gutmann, V.; Wychera, E. Inorg. Nucl. Chem. Lett. 1966, 2, 257. Gutmann, V . Coord. Chem. Reu. 1976, 18$225. (6) Marcus, Y. J . Solution Chem. 1984, 13, 599. (7) Dimroth, K.; Reichardt, C.; Siepmann, T.; Bohlmann, F. Justus Liebigs Ann. Chem. 1963, 661, 1. Reichardt, C. Solcent Effects in Organic Chemistry; Verlag Chemie: Weinheim, 1979.
0 1988 American Chemical Society
3614
The Journal of Physical Chemistry, Vol. 92, No. 12, 1988
Marcus et a].
TABLE I: Standard Molar Gibbs Free Energies of Transfer of Ions from Water, in kJ mol-', on the mol dm-3 Scale at 298 K, Based on the TATB Assumption" solventb MeOH EtOH 1-PrOH 1-BuOH TFE EG Me,CO PC H+ 10.4 11.1 9 3bb 5 50 Li+ 11 11 4.4 0 1Ohh 23.8 Na+ 14 17 8.2 19 -2 1o h h 14.6 K+ 16.4 17 9.6 20 39 -2 4 5.3 Rb+ 16 19 9.6 23 4 -1.0 cs+ 15 19 17 8.9 -7.0 4 1 4.9 6.6 50 1 18.8 9 Ag+ TI+ 7 4.1 3' 11.0 7 7c 12 NH4+ (5) Ba2+ 1 6.9h cu2+ 46p 28.9 43p 49ee (73)m Zn2+ 42" 27.4h (8l)hh (83)hh Cd2+ 22x 32.9h (70)hh (61)hh (64)gg (48)gg Hg2+ (47p (2P Pb2+ 4" 141 472 (78)hh 11 12 10.9 Me4N+ 6 3 -1 1 1 6 5' 7 Et4N+ -13 -109 -7 -6' Pr4N+ -22 (-6) -1 7c -2 1 -12 Bu4N+ -3 1 (-8) -25 -24.1 -21.2 -2 1 -20 Ph4As+ -32 -36.0 -7d -5.7d -6.7d -2d -7 Pic-6 -25 -24.1 -21.2 -20 -2 1 BPh4-36.0 -32 F16 56 29 -10 9 13.2 CI26 39.8 57 20.2 11.1 18.2 -8 7 42 Br22 24 30.0 12.9 19 22 17.3 -8 3 25 13.7 -12.6 (-17)' 1,1 9.1 17.0 N 27 43 7 CN8.6 36 48 5 7.0 SCN5.6 14 NO,12.5a 10 I7 22 c104-3 6.1 17" 8.8" 15" 3.1'' 12.4" 5.8" Tc04CHjC0216.0 -16.W CFqSOqsolvent FA NMF" DMF DMA DEA" NMPy MeCN NH,'
,-
H+ LI+ Na+
K+ Rb+ cs+ Ag+
TI+ ISH4+ Ba2+ cu2+
Zn2+ Cd'+ Hg2+ Pb2+ Me4h+ Et4N+ Pr4N+ Bu4N+ Ph4As+ PICBPh4F-
c1Br-
I 13N,CIT SCNNO,clodTc04CH,CO; CF,SO,-
-97 -35" -1 7 -12 -13 -1 5 -100 -28" -66" -181 -149 -1 52 -228
-10 -8 -4.3 -5 -6.0 -15.4 -1' -4ee
-20" -7 -6 -8 -7 -15" -10 -4ee
-28"
-32
-127 2.7'
-33'
-10.1'
43 33 25
-23.9 -7 -23.9 25 13.7 10.7 7.3 -7 11 13.3 7 -12 -1.6" 20
-33 -3 3
-18 -10 -9.6 -10.0 -9.7 -10.8 -20.8 -11.5
-2 1 .4h (-18) -29.6h -33.5h (-44)ZP -34' -5.3 -8.0 -17 -29 -38.5 -7 -38.5 51 48.3 36.2 20.4 -27 36 40 18.4 4 3.3" 66
-22u -12.1 -1 1.7 -8 -7" -29.0 -13" -27" (-7)hh -22"
-12 -10 -9 -1 1 -29 -1 2
-25 -35 -15 -1 1 -8 -10 -26 -15 -24
(-45)hh
-33 -22
(-8)hh -2200
-36"
-34'
-35' -3
-40
-38.1
-40
-40
-38.7
-40 51 37 19
54.9 44.0 21 -30 40
46
21
18
5.0" 70
1 oii
-12
46.4 25 15.1 8.1 6.3 60 -23.2 8.0 57.4h 6 8O,* 68.7h 42.2h (42)gg 64" 3 -7 -1 3 (-32)k -32.8 -4 -32.8 71 42.1 31.3 16.8 -1 5 37 35 14.4 21 2 6.87'' 61 -23'
The Journal of Physical Chemistry, Vol. 92, No. 12, 1988 3615
Energetics of Ion Transfer from Water to Solvents TABLE I (Continued)
solvent H+ Li+ Na+ K+ Rb+
CS+ Ag+
TI+
MeNO,
PhN02
9 sii 48 31.6' 15.4' 1l.W 5.6' 21 (16)'
33 38 36' 21e 19 18'
NH4+ Ba2+ CU2+
Zn2+ Cd?' Hg2+ Pb2+ Me4N+ Et4N+ Pr4N+ Bu~N' Ph4As+ PicBPh4F-
c1BrI-
2-CNPy"
16 6 13 (35) -57 -1
24 14
9 Yj
-50
(31)gg
-79
-4.6' -109 -2O.N -32.6' -32.6' 37.7' 29.W 18.91
13-
N3CNSCNNO,clodTcOi CH3COY CFjSOc
(15) 27
PyY -28
28 3I d 15 4.7J
4 -5 -16 -3 1 -36 -3e -36 (44)' 35 29 18 -23
(6Im 24d 10' 5ii
-2
-38 -5 -38
-39 -6 -39
34 21 19
31
20 16
DMSO -19.4 -1 5 -13.4 -1 3.0 -10.4 -13.0 -34.8 -21.4
TMS
HMPT
1,l-DCIE
1,2-DCIE
40'/
-26.6h -43" (-45)ee (-58) (-48)gg (-52)' -2 (-9)
(6Ihh -3 -4 -9 -10 -4 (-1 2)hh
- 17"' -16 - 10"" -7aM -44 -26""
62ee (76)hh (39)hh
(-52)hh -86"" -36""
(29)hh
29 30 29 28
25 26 25 24
18 11
16 5
-38'"
(-23)5 -33
-37.4
-36
-39
-27
-37.4
-36
-39
-27
40.3 27.4 10.4 (-4 1 25.8 35 9.1
47 35 21 (-14)' 41
58 46 30
58 43 31
-33 (65Y 52 38 25
22
20 22
7 16
24 -5
56'j
(-Ilk
49
-7
(50)
-14
OUnless otherwise noted, data are from ref 3 (the data for ammonia are at 240 K, those for tetramethylene sulfone and for 2-cyanopyridine are at 303 K). bThe abbreviations stand for the following names of the solvents: MeOH = methanol, EtOH = ethanol, 1-PrOH = 1-propanol, 1-BuOH = 1-butanol, T F E = 2,2,2-trifluoroethanoI, EG = 1,2-ethanediol, Me,CO = acetone, P C = propylene carbonate, FA = formamide, N M F Nmethylformamide, D M F = N,N-dimethylformamide, DMA = N,N-dimethylacetamide, DEA = N,N-diethylacetamide, NMPy = N-methylpyrrolidinone, MeCN = acetonitrile, MeNOz = nitromethane, PhNO, = nitrobenzene, Py = pyridine, 2-CNPy = 2-cyanopyridine, DMSO = dimethyl sulfoxide, T M S = tetramethylene sulfone, H M P T = hexamethylphosphoric triamide, 1,l-DCIE = 1,l-dichloroethane, 1,2-DCIE = 1,2-dichloroethane. CDanil de Namor, A. F.; Contreras, E.; Sigstad, E. J . Chem. Soc., Faraday Trans. 1 1983, 79, 1001. dHundhammer, B.; Solomon, T.; Alemu, H . J . Electroanal. Chem. 1983, 149, 179. eDanil de Namor, A. F.; Contreras, E.; Sigstad, E. J . Chem. Soc., Faraday Trans. 1 1983, 79, 2713. ILewandowski, A. Electrochim. Acta 1984, 29, 547. EAbraham, M. H.; Danil de Namor, A. F.; Schulz, R. A. J . Chem. SOC.,Faraday Trans. 1 1980, 76, 869. *Hedwig, G. R.; Owensby, D. A.; Parker, A. J. J . Am. Chem. SOC.1975, 97, 3888. 'Cox, B. G.; Waghorne, W . E. Chem. SOC.Reu. 1980, 9, 38 1. JDanil de Namor, A. F.; Ghousseini, L. J . Chem. Soc., Faraday Trans. 1 1984, 80, 2843. Ahrland, S . ; Ishiguro, S . ; Portanova, R. Aust. J . Chem. 1983, 36, 1805. 'Benoit, R. L.; Wilson, M . F.; Lam, S.-Y. Can. J . Chem. 1977, 55, 792. "'Vanysek, P. J . Electroanal. Chem. 1981, 121, 149. "Lemire, R. J.; Sears, P. G . J . Solution Chem. 1981, 10, 511. "Singh, P.; McLeod, I. D.; Parker, A. J. J . Solution Chem. 1982, 1 1 , 495. PCoetzee, J. F.; Istone, W. K. Anal. Chem. 1980, 52, 53. qKolling, S. Trans. Kans. Acad. Sei. 1962, 85, 61. 'Hundhammer, B.; Solomon, T.; Alemayu, B. J . Electroanal. Chem. 1982, 135, 301. 'Czapkiewicz, J.; Czapkiewicz-Tutaj, B.; Struck, D. Pol. J . Chem. 1978, 52, 2203. 'Gritzner, G. Inorg. Chim. Acta 1977, 24, 5. UGsaller,G.; Gritzner, G. 2.Phys. Chem. 1983, 130, 137. uGritzner, G. J . Electroanal. Chem. 1983, 144, 259. "Boeck, J.; Gritzner, G. 2.Phys. Chem. (Neue Fulge) 1982, 130, 181. "Case, B.; Parsons, R. Trans. Faraday SOC.1967, 63, 1224; data for lead chloride minus twice the chloride value given in this table. YPersson, I. Pure Appl. Chem. 1986, 58, 1153. IGritzner, G.; Geyer, E. Z . Phys. Chem. (Neue Fulge) 1981, 125, 7; adjusted with the value for transfer from water into acetonitrile, given by the linear relation found there to the K+ value. ""Kraml, G.; Gritzner, G . J . Chem. SOC.,Faraday Trans. 1 1985,81, 2875. "*Value for HCI from H . D. Wehle (quoted by: Schwabe, K.; Queck, C. Abhandl. Saechs. Akad. Wissen. 1979, 53, No. 3, and for CI- from this table. CCSchindewolf,U. Ber. Bunsen-Ges. Phys. Chem. 1982, 86, 887. ddChantooni, M. K.; Kolthoff, I. M. J . Phys. Chem. 1978, 82, 994. "Lewandowski, A. Electrochim. Acta 1985, 30, 311; 1986, 31, 59; negligible liquid junction assumption. ffGomaa, E. A. Thermochim. Acta 1985, 91, 235. EtBalyatinskaya, L. N . Russ. Chem. Reu. 1979, 48, 418; adjusted for the use of the ferrocene assumption by data obtained for Ag+ on this assumption by Badoz-Lambling, J.; Bardin, J. C. Electrochim. Acta 1974, 19, 725; and the Ag+ data from the present table. hh Calculated from the data of Gritzner, G. J . Phys. Chem. 1986, 90, 5478; relative to his data for transfer into MeCN and his data for Ag+ and the present data for transfer from water to MeCN and those for Ag'. "Neck, V.; Kanellakopulos, B.; Kim, J. I. Kernforschungszentrum Report KfK 1985, 3998. "Badoz-Lambling, J.; Bardin, J. C. Electrochim. Acta 1974, 19, 725; adjusted for fic+/foc reference value with the CI- value from this table. f
by it, 1000 = ( 4 0 0 ~ / 3 ) ( r / n m ) ~The . polarizability of an ion was expressed in terms of its normalized molar refractivity, RD/10 (with RD given in em3 mol-'). A final property of the ions considered was its softness parameter,'^^ 0 . However, for the larger ions, this was not independent of 1000 or of RD/10 and played a significant role only for smaller ions, with r E 0.25 n m or less. ~
Chem 1972, I O , 659. (9) Marcus, Y . Thermochim Acta 1986, 104, 389
( 8 ) Marcus, Y . Isr J
Input Data The solvents and ions that are considered in this paper are those for which standard molar Gibbs free energies 4,,Go(X,W-S) or enthalpies 4,,Ho(X,W-S) of transfer from water t o nonaqueous solvents are available, on the basis of a reliable extrathermodynamic assumption. This is necessary for the relation of these quantities to solvation properties of individual ions. The extrathermodynamic assumption that has so far been found t o be the least objectionable, and also to be applicable t o both Gibbs
3616 The Journal of Physical Chemistry, Vol. 92, No. 12, 1988 TABLE 11: Standard Molar Enthalpies of Transfer of Ions from Water, in solventb D 2 0 MeOH EtOH I-PrOH PC NH3 H+ -7.4' 14.6' 44 Li+ 1.9 -21.7 -20.2 -18.4 2.8 -45 Na+ 2.6 -20.7 -19.4 -18.8 -10.5 -36 -19.0 -19.6 -18.3 -22.5 -26 K+ 2.8 Rb+ 2.9 -16.5 -24.9 -25 cs+ 3.0 -14.1 -11.8" -12.7 -27.5 -33 Ag+ 2.3 -20.9 -11.1 -106 NH4+ 1.3 -18.8" -26.5" -28.0 -19.8 Ca2+ 5.4 -10.9 -98 Sr2+ 5.7 -15.1 -109 Ba2+ 6.1 -60.6 -21.8 -102 Zn2+ -45.6' Cd2+ -40.4e Me4N+ 1.8 0.3 0.2 -16.3' Et4N+ 0.9 7.1 9.6 0.6'
Marcus et al. kJ mol-', Based on the TATB Assumption" solventb D,O MeOH EtOH 1-PrOH Pr4N+ -0.2 15 -1.0 20 21.3 Bu~N+ Ph4As' 0.7 -1.0 0.0" 1.5 Pic-0.9s BPh40.7 -1.0 0.0" 1.5 F -2.6 13.8' CI-0.2 8.4 10.4 8.4 Br0.4 4.5 5.5 2.5 11.0 -1.0 -0.7 -1.5 iV30.5 SCN-3.2' Clod-0.2 -3.1 -2.7 0.0 3.6 BF4CF3SOj4.6
solvent Pyk -43.9s
H+ Li+ Na' -30.3 K+ -24.1' Rb+ -27.8' cs+ -28.1' Ag+ -106 NH4+ -36.4' Ba2+ Zn2+ Cd2+ Hg2+ -160' Me4N+ Et4N+ -3.7
FA -6.0 -16.5 -17.9 -17.8 -17.7 -40.2k -23.9k -27.5k
MeNola" H+ Li+ Na+ K+ Rb+ cs+ Ag+ NH4+ Ba2+ Zn2+ Cd2+ Hg2+ Me4N+ Et4N+
25.8 11.5 -13.5 -17.7 -16.6
-13.5 -1.8
NMF" NEA"
-22.5
-7.1 -8.6 -24.0
-41.3
-2.1' 5.5'
MeCN 3.0' -13.0' -13.3 -22.9 -24.6 -26.1' -52.7
NH,
-13.1 26.2 15.2 -1.6 16.7
6 -16 -29
-16.3
solvent DMF -25.4 -32.4 -35.7 -36.1 -34.6 -3 5
DMAd NMPy
-41.2'
-85.5' -62.7e -63.3'
-26" -41 -47
-53.2'
-1 3
-4.0',d solvent DMSO T M S
-11.25 -27.1 -29.2 -35.4 -38.1' -33.0 -53.3 -35.3s -8.5' -78.5' 20.1' -62.2e 8.2' -70.Se -76 -15.3 -16.4 1.8C.d 3.3'
PC 1 1.6c 1 8.4c -13.1
-7.3'
HMPT
73 12q -16 -26 -28 -26 -14
-57.4 -50.6 -46.6 -43.8 -45.0
-9.2C'd
-25.1 -28.0 -27.6 -27.2
-34.1 -6.1
-7.6
Pr4N+ Bu4N+ Ph4As+ PicBPh4-
11.5 21.5 -6.9 -4.0 -6.9
F
c11-
21.2 7.1 -7.8
N3SCN-
c104BF4CF3SO3-
-19.2
-7.3
14.2
-11.8
MeN0204 MeCN
Br-
-15.9 -10.0
FA NMF" NEAO D M F DMAd NMPy 16.d 9y 26.V 24.6 10.9C,d 7.7' 6.4C.d -0.5 -7.6 -7.3 -17.2 -13.7" -17
Pr4N+ Bu~N+ 7.9 Ph,As+ -22.8 Pic-12.OS BPh4-22.8 -0.5 F' 19.9 c128.2 3.5 Br10.9 -1.5 I-7.3 -6.8 N3SCN-4.7 -10.9' C104-18.8 BF4-20.8' C F , S O c -3.9' 1.5"
1.2-DCIE
-64.2'' -1 22.0'J -74.8"" -93 I5'J -164
Pyh
-17.2
-13.7
-0.4 -4.3 -11.0
17.9 0.6 -15.0 2.v
-11.0
-23.4
35.6 17.2 -0.7 -1.0' -10.0' -15.3
-17 27 13 2 -11
-3.4" solvent DMSO TMS
10.68 16.V 19.1C,d 25.Q -11.1 -10.6 -12.4' -12.3s -11.1 -10.6 3w 19.3 20.0 8.0 4.6 -7.6 -11.5 8.8 -2.5' -4.99 -4.9' -16.08 -18.2 -12.9' -14.5' 0.8' 2.15
HMPT
1,2-DCIE
174 26s -11
1.6 5.3 -25.8
9.0 -22.8
-11
-25.8
-22.8
38.2 17.7 -5.8 15 -4.6 -20.7
16.3 0.8 -15.5
27 13 -8 15 -184
-24.3
-0.5e.x
"The data are the selected values from ref 4, unless otherwise noted, valid for 298 K, except for ammonia (240 K) and tetramethylene sulfone (303 K). bThe abbreviations for the solvents are defined in Table I, except for N E A = N-ethylacetamide, 'Castagnolo, M.; Sacco, A.; deGiglio, A. J. Chem. Soc., Faraday Trans. I 1984, 80, 2669. dKondo, Y.; Shiotami, H.; Kusabayashi, S. J . Chem. SOC.,Faraday Trans. I 1984, 80, 2145. 'Hedwig, G. R.; Owensby, D. A,; Parker, A. J. J. A m . Chem. SOC.1975, 97, 3888. fDanil deNamor, A. F.; Ghousseini, L.; Schulz, R. A. J . Chem. SOC.,Faraday Trans. I 1984, 80, 1323. ZMiyaji, K.; Morinaga, K. Bull. Chem. SOC.Jpn. 1983, 56, 1861. *Ahrland, S.; Ishiguro, S.; Portanova, R. A u s f . J . Chem. 1983, 36, 1805. 'Tomkins, R. P. T.; Feakins, D.; Waghorne, W. E. J . Chem. Thermodynam. 1977, 9, 707. 'Cox, B. G.; Waghorne, W. E. Chem. SOC.Rec. 1980, 9, 381. kHedwig, G. R.; Parker, A. J. J. Am. Chem. SOC.1974, 96, 6589. 'Cox, B. G.; Hedwig, G. R.; Parker, A. J.; Watts, D. W . Ausf. J . Chem. 1974, 27, 477. "Abraham, M. H.; Ah-Sing, E.; Danil deNamor, A. F.; Hill, T.; Nasezadeh, A,; Schulz, R. A. J. Chem. Soc., Faraday Trans. 1 1978, 74, 359. "Abraham, M. H.; Danil deNamor, A. F.; Schulz, R. A. J. Chem. SOC.,Faraday Trans. 1 1980, 76, 869. "N-Ethylacetamide, from A,,B"(MeOH+NEA) of Fuchs, R.; Bear, J . L.; Rodewald, R. F. J . A m . Chem. SOC.1969, 91, 5797; and A,,Ho(W+MeOH) from this table. PArnett, E. M.; Moriarty, T. C. J . Am. Chem. SOC.1971, 93, 4908. qChoi, Y.-S.; Criss, C. M. J . Chem. Eng. Data 1977, 22, 297; with the value for 1- taken as -8 kJ mol-'. 'Robinette, A. F.; Amis, E. S. Ado. Chem. Ser. 1979, 177, 355. Johnsson, M.; Persson, I. Inorg. Chim. Acfa 1987, 127, 25, 43. 'Ahrland, S. Pure Appl. Chem. 1982, 54, 1451. "Vandyshev, V. N.; Korolev, V. P.; Krestov, G. A. Z h . Obshch. Khim. 1985, 55, 2409. rMecik, M.; Chudziak, A. J. Solution Chem. 1985, 14, 653. "Hedwig, G. R.; Parker, A. J. J . A m . Chem. SOC.1974, 96, 6589. "Castagnolo, M.; Petrella, M.; Inglese, A,; Sacco, A.; DellaMonica, M. J . Chem. Soc., Faraday Trans. I 1983, 79, 221 1; used A,,Ho(CF,SO
