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Descriptors for ferrocene and some substituted ferrocenes
Accepted Manuscript Descriptors for ferrocene and some substituted ferrocenes
Michael H. Abraham, William E. Acree PII: DOI: Reference:
S0167-7322(16)34299-4 doi: 10.1016/j.molliq.2017.02.059 MOLLIQ 6972
To appear in:
Journal of Molecular Liquids
Received date: Revised date: Accepted date:
1 January 2017 13 February 2017 15 February 2017
Please cite this article as: Michael H. Abraham, William E. Acree , Descriptors for ferrocene and some substituted ferrocenes. The address for the corresponding author was captured as affiliation for all authors. Please check if appropriate. Molliq(2017), doi: 10.1016/j.molliq.2017.02.059
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ACCEPTED MANUSCRIPT 1
Descriptors for ferrocene and some substituted ferrocenes
and William E. Acree, Jr
b
IP
c
a*
T
Michael H Abraham
Department of Chemistry, 1155 Union Circle Drive #305070, University of North
CR
Texas, Denton, TX 76203-5017, USA Email: [email protected]
US
Keywords: ferrocene, acetylferrocene, acetoacetylferrocene, gas-solvent partition coefficients, water-solvent partition coefficients, solubility, linear free energy
AN
relationships
M
ABSTRACT
We have used literature data on solubilities in 58 solvents to obtain Abraham (Absolv)
ED
descriptors for ferrocene. The required descriptor E was obtained through known measurements of molar refraction, and the V descriptor was obtained through comparison
PT
of partial molal volumes with McGowan volumes, Vx, for 58 compounds. Ferrocene is quite hydrophobic, with our calculated water-octanol partition coefficient as 3.70 ( log
CE
Ps), it has no hydrogen bond acidity, only a small hydrogen bond basicity, but a significant dipolarity. Descriptors for a number of derivatives of ferrocene were also
AC
obtained from solubility data; these derivatives were acetylferrocene, diacetylferrocene, acetoacetylferrcene
and
diacetoacetylferocene.
In
addition,
descriptors
for
alkylferrocenes were estimated by comparison. Substituent effects on ferrocene are very similar to substituent effects on purely organic compounds, and could be used to estimate descriptors for a variety of monosubstituted ferrocenes.
* Corresponding author. Tel.: 020-7679-4639; fax: 020-7679-7463. E-mail address: [email protected] (M. H. Abraham) 1
ACCEPTED MANUSCRIPT 2
1. Introduction There is considerable recent interest in ferrocene and its derivatives, especially with regard to nonlinear optical processes [1, 2], and there have been several new solubility
T
studies, especially by De Fina et al. [3] who compared observed solubilities with those
IP
predicted by mobile order theory. We have previously determined Abraham (or Absolv)
CR
descriptors for ferrocene [4], using a very restricted data set, but there is now much more solubility data available [3, 5, 6] and we have also been able to set out general methods
US
for the calculation of some of the descriptors. Our aim was therefore to use all this recent data on ferrocene [5-12] to obtain more reliable descriptors for ferrocene, and then for
AN
some of its derivatives. 2. Methodology
M
Our method is based on two general linear free energy relationships, Eqs. (1) and (2), that can be used to correlate and to predict the transfer of neutral solutes from water
ED
to organic solvents and from the gas phase to organic solvents. The dependent variable in Eq. (1) is log P, where P is the molar water to solvent partition coefficient for a series of
PT
solutes, and in Eq. (2) is log K where K is the dimensionless gas phase to solvent partition coefficient for a series of solutes [13-17]. The general method has been reviewed several
CE
times [13-17]; the review by Clarke and Mallon [17] is particularly comprehensive.
(1)
AC
Log P = c + e E + s S + a A + b B + v V Log K = c + e E + s S + a A + b B + l L
(2)
In Eq. (1) and (2) the independent variables, or descriptors, are properties of the neutral solutes as follows [13-17]: E is the solute excess molar refraction in cm3 mol-1/10, S is the solute dipolarity/polarizability, A is the overall solute hydrogen bond acidity, B is the overall solute hydrogen bond basicity, V is McGowan’s characteristic molecular volume in cm3 mol-1/100 and L is the logarithm of the gas to hexadecane partition coefficient at
2
ACCEPTED MANUSCRIPT 3
298 K. The coefficients in Eq. 1 and Eq. 2 are shown in Table 1 for partition from water to the various solvents that we shall encounter [18 - 41].
Table 1. Coefficients in Eq. (1) and Eq. (2) for partitions from water and from the gas phase to
0.560 0.670 0.642 0.619 0.585 0.668 0.667 0.784 0.782 0.555
Trichloromethane Tetrachloromethane 1,2-Dichloroethane
0.191 0.199 0.183
-1.710 -2.061 -1.647 -1.713 -1.734 -1.644 -1.617 -1.678 -1.982 -1.737
a
b
v
-3.578 -3.317 -3.480 -3.532 -3.435 -3.545 -3.587 -3.740 -3.517 -3.677
-4.939 -4.733 -5.067 -4.921 -5.078 -5.006 -4.869 -4.929 -4.293 -4.864
4.463 4.543 4.526 4.482 4.582 4.459 4.433 4.577 4.528 4.417
CR
Heptane Octane Nonane Decane Dodecane Hexadecane Cyclohexane Methylcyclohexane 2,2,4-Trimethylpentane
0.333 0.325 0.223 0.240 0.160 0.114 0.087 0.159 0.246 0.318
Hexane
s
US
e
AN
c
M
Solvent, Eq. 1
IP
T
various solvents.
-0.403 -1.159 -0.134
-3.112 -3.560 -2.801
-3.514 -4.594 -4.291
4.395 4.618 4.180
0.222
0.273
-0.569
-2.918
-4.883
4.456
0.047
0.686
-0.943
-3.603
-5.818
4.921
0.142
0.464
-0.588
-3.099
-4.625
4.491
Toluene Ethylbenzene
0.143 0.093
0.527 0.467
-0.720 -0.723
-3.010 -3.001
-4.824 -4.844
4.545 4.514
o-Xylene
0.083
0.518
-0.813
-2.884
-4.821
4.559
m-Xylene
0.122
0.377
-0.603
-2.981
-4.961
4.535
p-Xylene
0.166
0.477
-0.812
-2.939
-4.874
4.532
Dibutylether Methyl tert-butylether
0.203 0.341
0.369 0.307
-0.954 -0.817
-1.488 -0.618
-5.426 -5.097
4.508 4.425
1,4-Dioxane
0.098
0.350
-0.083
-0.556
-4.826
4.172
Tetrahydrofuran
0.207
0.372
-0.392
-0.236
-4.934
4.447
AC
Benzene
CE
Carbon disulfide
PT
1-Chlorobutane
ED
0.105 0.523 0.294
3
ACCEPTED MANUSCRIPT 0.351
0.223
-0.150
-1.035
-4.527
3.972
Ethyl acetate
0.328
0.369
-0.446
-0.700
-4.904
4.150
Butyl acetate
0.248
0.356
-0.501
-0.867
-4.973
4.281
Propanone
0.313
0.312
-0.121
-0.608
-4.753
3.942
Acetonitrile
0.413
0.077
0.326
-1.566
-4.391
3.364
Dimethylsulfoxide
-0.194
0.327
0.791
1.260
-4.540
3.361
Formamide
-0.171
0.070
0.308
0.589
T
2.432
Dimethylformamide
-0.305
-0.058
0.343
0.358
-4.865
4.486
Pyridine
-0.046
0.298
0.000
0.558
4.292
Ethanol Propan-1-ol
0.222 0.148
0.471 0.436
-1.035 -1.098
CR
-4.504
0.326 0.389
3.857 4.036
Propan-2-ol
0.102
0.315
-1.020
0.532
-3.865
4.023
Butan-1-ol
0.152
0.438
US
-3.596 -3.893
-1.177
0.096
-3.919
4.122
Butan-2-ol
0.194
0.383
-0.956
0.134
-3.606
3.829
2-Methylpropan-1-ol
0.161
0.310
-1.069
0.183
-3.774
4.040
2-Methylpropan-2-ol
0.211
0.171
-0.947
0.331
-4.085
4.109
Pentan-1-ol
0.150
0.536
-1.229
0.141
-3.864
4.077
0.115
0.455
-1.331
0.206
-3.745
4.201
0.073
0.360
-1.273
0.090
-3.770
4.273
0.177
0.316
-1.125
0.306
-4.112
4.178
0.115
0.492
-1.164
0.054
-3.978
4.131
2-Methylpentan-1-ol
0.074
0.423
-1.228
0.143
-4.031
4.221
4-Methylpentan-2-ol
0.055
0.369
-1.340
0.211
-4.035
4.322
Heptan-1-ol
0.035
0.398
-1.063
0.002
-4.342
4.317
Octan-1-ol
-0.034
0.489
-1.044
-0.024
-4.235
4.218
0.061
0.459
-1.067
-0.178
-4.117
4.120
Decan-1-ol
-0.058
0.616
-1.319
0.026
-4.153
4.279
Ethylene glycol
-0.243
0.695
-0.670
0.726
-2.399
2.670
Wet octan-1-ol
0.088
0.562
-1.054
0.034
-3.460
Methanol
0.276
0.334
-0.714
0.243
-3.320
3.814 3.549
AC
Hexan-1-ol
ED
CE
2-Methylbutan-2-ol
PT
Pentan-2-ol 3-Methylbutan-1-ol
2-Ethylhexan-1-ol
a
AN
Methyl acetate
M
4
4
IP
-3.152
ACCEPTED MANUSCRIPT 5
Solvent Eq. 2
c
e
Hexane
0.320
0.000
Heptane
0.275
-0.162
Octane
0.215
Nonane
0.200
Decane
0.156
0.297 0.294 0.262 0.260 0.311 0.293 0.251 0.171 0.260 0.096 0.065 3.813
3.724 3.697 3.545 -3.212 -2.936 -2.675 -2.275 -1.809 -3.212 0.916 0.454 4.841
3.637 3.609 3.483 3.323 3.102 3.812 2.415 1.918 3.323 0.681 0.254 -0.869
T
-0.833 -0.795 -0.575 -0.465 -0.368 -0.335 -0.252 -0.159 -0.465 -0.040 -0.001 2.549
IP
0.353 0.328 0.213 0.175 0.085 0.138 0.124 0.131 0.175 0.042 -0.023 0.577
CR
0.238 0.239 0.243 0.172 0.063 -0.040 -0.142 -0.221 0.172 -0.252 -0.173 -0.994
s
a
b
l
0.000
0.000
0.000
0.945
0.000
0.000
0.000
0.983
-0.049
0.000
0.000
0.000
0.967
-0.145
0.000
0.000
0.000
0.980
-0.143
0.000
0.000
0.000
0.989
0.017
0.000
0.000
0.000
0.000
0.989
0.000
0.000
0.000
0.000
0.000
1.000
0.163
-0.110
0.000
0.000
0.000
1.013
0.318
-0.215
0.000
0.000
0.000
1.012
2,2,4-Trimethylpentane
0.264
-0.230
0.000
0.000
0.000
0.975
Trichloromethane
0.157
-0.560
1.259
0.374
1.333
0.976
AC
ED
M
AN
US
96% vol Ethanol-water 95% vol Ethanol-water 90% vol Ethanol-water 80% vol Ethanol-water 70% vol Ethanol-water 60% vol Ethanol-water 50% vol Ethanol-water 40% vol Ethanol-water 30% vol Ethanol-water 20% vol Ethanol-water 10% vol Ethanol-water Gas to water
Tetrachloromethane
0.217
-0.435
0.554
0.000
0.000
1.069
1,2-Dichloroethane
0.017
-0.337
1.600
0.774
0.637
0.921
1-Chlorobutane
0.130
-0.581
1.114
0.724
0.000
1.016
Carbon disulfide
0.101
0.251
0.177
0.027
0.095
1.068
Benzene
0.107
-0.313
1.053
0.457
0.169
1.020
Toluene
0.121
-0.222
0.938
0.467
0.099
1.012
Ethylbenzene
0.059
-0.295
0.924
0.573
0.098
1.010
o-Xylene
0.064
-0.296
0.934
0.647
0.000
1.010
Dodecane
Cyclohexane
CE
Methylcyclohexane
PT
Hexadecane
5
ACCEPTED MANUSCRIPT 0.071
-0.423
1.068
0.552
0.000
1.014
p-Xylene Dibutylether
0.113 0.165
-0.302 -0.421
0.826 0.760
0.651 2.102
0.000 -0.664
1.011 1.002
Methyl tert-butylether
0.278
-0.489
0.801
2.495
0.000
0.993
1,4-Dioxane
-0.034
-0.354
1.674
3.021
0.000
0.919
Tetrahydrofuran
0.189
-0.347
1.238
3.289
0.000
0.982
Methyl acetate
0.134
-0.477
1.749
2.678
T
0.876
Ethyl acetate
0.182
-0.352
1.316
2.891
0.000
0.916
Butyl acetate
0.147
-0.414
1.212
2.623
0.954
Propanone
0.217
-0.387
1.733
3.060
0.000
0.866
Acetonitrile
-0.007
-0.595
2.461
CR
0.000
2.085
0.418
0.738
Dimethylsulfoxide
-0.556
-0.223
2.903
5.037
0.000
0.719
Formamide
-0.800
0.310
2.292
4.130
1.933
0.442
Dimethylformamide
-0.391
-0.869
2.107
3.774
0.000
1.011
Pyridine
-0.123
-0.588
1.991
4.363
0.000
0.942
Ethanol
0.017
0.867
3.894
1.192
0.846
Propan-2-ol
Butan-2-ol
CE
2-Methylpropan-1-ol 2-Methylpropan-2-ol
AC
Pentan-2-ol
3-Methylbutan-1-ol 2-Methylbutan-2-ol
M
IP
-0.246
0.749
3.888
1.076
0.874
-0.048
-0.324
0.713
4.036
1.055
0.884
-0.004 -0.017
-0.285 -0.376
0.768 0.852
3.705 3.740
0.879 1.161
0.890 0.867
0.012
-0.407
0.670
3.645
1.283
0.895
0.053
-0.443
0.699
4.026
0.882
0.907
-0.002
-0.161
0.535
3.778
0.960
0.900
-0.031
-0.325
0.496
3.792
1.024
0.934
-0.052
-0.430
0.628
3.661
0.932
0.937
0..014
-0.435
0.573
3.965
0.811
0.943
-0.014
-0.205
0.583
3.621
0.891
0.913
-0.061
-0.289
0.539
3.787
0.911
0.923
-0.047
-0.376
0.398
3.845
0.897
0.952
-0.056
-0.216
0.554
3.596
0.803
0.933
a
Hexan-1-ol 2-Methylpentan-1-ol
a
4-Methylpentan-2-ol
a
Heptan-1-ol
0.000
-0.042
PT
Butan-1-ol
Pentan-1-ol
-0.232
ED
Propan-1-ol
AN
m-Xylene
US
6
6
ACCEPTED MANUSCRIPT 7
Octan-1-ol
0.749
0.943
-0.085
-0.384
0.616
3.383
0.673
0.959
-0.139
-0.090
0.356
3.547
0.727
0.958
-0.887
0.132
1.657
4.457
2.355
0.565
-0.222 -0.039 -0.032 -0.040 -0.084 -0.253 -0.438 -0.631 -0.851 -1.074 -1.258 -1.364 -1.447 -1.271
0.088 -0.338 -0.181 -0.200 -0.280 -0.278 -0.255 -0.186 -0.063 0.075 0.194 0.383 0.446 0.822
0.701 1.317 0.980 1.024 1.180 1.400 1.548 1.646 1.806 2.076 2.300 2.385 2.536 2.743
3.473 3.826 3.940 3.950 3.959 4.000 4.040 4.054 4.050 4.020 4.000 3.950 3.905 3.904
1.477 1.396 1.379 1.400 1.474 1.775 2.074 2.355 2.745 3.196 3.713 4.280 4.750 4.814
0.851 0.773 0.802 0.795 0.757 0.715 0.659 0.584 0.479 0.347 0.206 0.065 -0.052 -0.213
b
T
96% vol Ethanol-water 95% vol Ethanol-water 90% vol Ethanol-water 80% vol Ethanol-water 70% vol Ethanol-water 60% vol Ethanol-water 50% vol Ethanol-water 40% vol Ethanol-water 30% vol Ethanol-water 20% vol Ethanol-water 10% vol Ethanol-water Gas to water
IP
Methanol
CR
Wet octan-1-ol
Coefficients for ethanol-water mixtures from this work, using data from
ED
b
3.507
US
Ethylene glycol
This work.
0.561
AN
Decan-1-ol
a
-0.214
M
2-Ethylhexan-1-ol
-0.147 a
PT
[23, 31]
CE
Most of the data we shall encounter is in the form of solubilities, Ss, in various solvents. These can be transformed into water to solvent partition coefficients through
AC
Eq. (3) where Sw is the solubility in water. Eq. (3) is valid only if no hydrate in water or solvate in the solvent is formed – that is the same species must be in equilibrium with water and the solvent. P = Ss/Sw or log P = log Ss – log Sw
(3)
Then values of P obtained from solubilities can then be transformed into corresponding gas to solvent partition coefficients, Ks, through Eq. (4), where Kw is the gas to water partition coefficient. 7
ACCEPTED MANUSCRIPT 8
Ks = P*Kw or log Ks = log P + log Kw
(4)
Once values of log P and log Ks are available for a given solute, a set of simultaneous equations can be set up and solved for the unknown descriptors E, S, A, B, V and L and the (usually) unknown value of log Kw. Sometimes the required value of log Sw in Eq. 3
T
may not be known, in which case it can be treated as another unknown to be obtained
IP
through solution of the simultaneous equations. The ‘Solver’ add-on to the Microsoft
CR
Excel program provides a particularly convenient method for the solution of these simultaneous equations. Since the number of equations is always larger than the number
US
of unknowns, a trial-and-error procedure is adopted to obtain the unknowns that give the best-fit to the equations.
AN
It is a considerable advantage to be able to deduce the value of some of the descriptors, and hence to reduce the number of unknowns. For neutral organic
M
compounds, the McGowan volume, Vx [42], can be calculated from the McGowan atomic fragments, shown in Table 2 [42, 43], together with the subtraction of 6.56 cm -1
for any bond in the molecule, single, double and triple bonds all being counted as
ED
mol
3
the same. This is straightforward for organic molecules but in the case of ferrocene it is
PT
not clear how many ‘McGowan’ bonds there are. Each cyclopentadienyl entity has 10 bonds, making a total of 20, but an extra two bonds between the cyclopentadienyl groups
CE
and the iron atom may be counted, making 22 bonds in all. Calculations of Vx will then be Vx = 10*8.71 + 10*16.35 + 1.03 – 20 *6.56* = 120.43 or Vx = 10*8.71 + 10*16.35 3
-1
AC
+ 1.03 – 22 *6.56* = 107.31 cm mol . Tran et al. [44] have determined partial molal volumes in acetonitrile, Vm, for ferrocene and a large number of other compounds for which we can calculate Vx. There is a good correlation between the two sets of volumes shown in Eq. 5 and Eq. 6, where we forced the plot through the origin. N is the number of compounds, SD the standard deviation, R the correlation coefficient and F is the F2
statistic. PRESS and Q are the leave-one-out statistics and PSD is the predicted standard deviation.
8
ACCEPTED MANUSCRIPT 9
Vx = -10.237 + 0.9482 Vm
(5)
2
2
N = 58, SD = 6.05, R = 0.993, F = 7531.6, PRESS = 2181.40, Q = 0.992, PSD = 6.24
Vx = 0.8895 Vm
(6)
T
N = 58, SD = 7.74, PRESS = 3534.0, PSD = 7.87
AN
US
CR
IP
With Vm = 141.9 [44], Vx = 124.3 ± 6.2 from Eq. 5 or 126.2 ± 7.9 from Eq. 6, in reasonable agreement with Vx = 120.43 by the McGowan method with 20 bonds. We can then use the McGowan method to calculate Vx for any ferrocene, noting that there are no bonds between the cyclopentadienyl groups and the iron atom. Previously [4] we took Vx for ferrocene as 112.1 but the present value of 120.43 is much to be preferred.
Ge 31.02 Sn 39.35
P
24.87
As 29.42
O 12.43
ED
Si 26.83
N 14.39
S
22.91
Sb 37.74
Se 27.81
Br 26.21
Te 36.14
I
34.53
Fe
2+
1.03
Fe
3+
0.78
Co
3+
0.78
Cr
3+
1.08
CE
Pb 43.44
F 10.48 Cl 20.95
PT
H 8.71 C 16.35
M
Table 2 3 -1 Atomic volumes, Vx, in cm mol
o
The E-descriptor can be calculated from a liquid refractive index, η, at 20 C and a
AC
value of V (= Vx/100). Experimental values of η for some alkylferrocenes are available [45], and if V is calculated in the same way as for ferrocene, values of E are obtained as shown in Table 3. There is a good plot of E versus the number of carbon atoms and this was used to smooth the values – the taken values are in column 3. For ferrocene itself, 3
Aroney et al. [46] determined the molar refraction as 50.4 cm from which we can deduce that η = 1.629 whence E = 1.394, in good agreement with values for the alkylferrocenes.
9
ACCEPTED MANUSCRIPT 10
Table 3 Values of the E-descriptor for ferrocene and some alkylferrocenes
Ferrocene
1.394
E taken
a
1.394
1.409
Propylferrocene
1.393
1.393
Butylferrocene
1.320
1.373
Pentylferrocene
1.392
1.366
Diethylferrocene
1.373
1.373
CR
1.409
AN
Ethylferrocene
See text.
3. Results and discussion
ED
M
a
1.394
US
Methylferrocene
T
E from exp η
IP
Compound
Ferrocene. By far the largest data set on experimental solubilities of ferrocene is
PT
that of De Fina et al. [3]. A number of other workers [8, 12] have recorded solubilities in a few of the same solvents as used by De Fina et al. [3], but we just used the De Fina data
CE
for consistency. Solubilities are available in a number of solvents not studied by De Fina et al., viz: dodecane and trichloromethane [4], formamide [7], tetrahydrofuran and
AC
dimethylformamide [47] and some water-ethanol mixtures [9]. We did not use the solubility in trichloromethane [4], which was very much larger than calculated ( log Ss obs = 0.373, log Ss calc = -0.177). It is possible that trichloromethane forms a solvate with ferrocene. Fedorov et al. [5] determined the solubility of ferrocene in watermethanol mixtures, but their given solubilities in water and methanol are so different to other recorded solubilities, and to our calculated solubilities, that we did not use any of their data. We were left with solubilities in 58 solvents, that could be transformed into 58 log Ps and 58 log Ks values through Eq. 3 and Eq. 4. These yield 116 equations, and with 10
ACCEPTED MANUSCRIPT 11
two extra equations in log Kw we have a total of 118 equations from which to derive descriptors. These 118 equations were solved with SD = 0.077 log units, to give the descriptors in Table 4.The value of 2.12 for log Kw is in good agreement with an observed value of 2.00 [4], and our value of -4.619 for log Sw is in reasonable agreement with various recorded experimental values [4], viz: - 4.47, - 4.37, - 4.30 and - 4.17). Apart from the B (and A) descriptor, those for ferrocene are not particularly close to
T
those for two cyclopenta-1,3-diene molecules, see Table 4. There is really no other
CR
IP
molecule with which to compare descriptors.
Table 4
E
Cyclopentadiene
0.417
0.35
Ferrocene
1.394
0.90
Acetylferrocene
1.537
1.56
Diacetylferrocene
1.680
2.70
Acetoacetylferrocene
1.804
Diacetoacetylferrocene 2.214
A
B
0.00
V
0.12
Log Kw
L
0.6185
2.222
1.2043
6.003
2.12
-4.62
0.00
0.83 1.5018
7.861
6.56
-1.49
0.00
1.06 1.7993 10.170
10.39
-1.72
1.83
0.00
0.95 1.7993
9.595
7.75
-3.72
2.88
0.00
1.64 2.3943 13.146
13.67
-3.78
ED
M
0.23
0.00
0.25
1.3452 6.424
2.137
1.409 0.89
0.00
0.25
1.4861 6.899
2.035
1.393 0.90
0.00
0.25
1.6270 7.380
1.936
Butylferrocene
1.373 0.89
0.00
0.25
1.7679 7.850
1.784
Pentylferrocene
1.366 0.90
0.00
0.25
1.9088 8.376
1.695
Ethylferrocene
1.394 0.89
AC
CE
Propylferrocene
Log Sw
0.00
PT
Methylferrocene
S
AN
Compound
US
Calculated descriptors for ferrocene and substituted ferrocenes
We can compare calculated and observed log Ps and log Ss for the various solvents we have used, noting that log Ss (calc) = log Ps (calc) – 4.619. For the 58 calculated and observed values in Table 5, the average error, AE, = 0.002, the absolute average error, AAE = 0.056, the root mean square error, RMSE = 0.0758 and SD = 0.0764 log units, so that our method gives a good account of the solubility of ferrocene in a large range of solvents. Predictions of log Ps and log Ss can be made for any other solvent for which we have coefficients. Our calculated value of log Ps for partition into wet octanol is 3.70 as 11
ACCEPTED MANUSCRIPT 12
compared to other calculated values of 1.78 [48] and 3.28 [49], and an experimental value of 3.5 [50]. Thus ferrocene is quite hydrophobic, with a reasonably large value of log Ps into octanol. Ferrocene has zero hydrogen bond acidity and only a small hydrogen bond basicity. It does have, however, a substantial dipolarity, with S = 0.90. Note that the ACD ChemSketch program [51] cannot calculate log Ps for ferrocene.
T
Table 5 -3
Log Ps
ED
CE
AC
Log Ss
Calc -0.829 -0.855 -0.722 -0.815 -0.878 -0.858 -0.861 -0.522 -0.622 -0.913 -0.280 -0.117 -0.306 0.099 -0.034 -0.046 -0.224 -0.185 -0.215 -0.203 -0.603 -0.451 -0.213 -0.046 -0.368
US
Obs 3.854 3.847 3.841 3.830 3.822 3.796 3.758 4.098 4.038 3.739 4.466 4.588 4.366 4.622 4.560 4.501 4.413 4.436 4.397 4.414 4.101 4.156 4.606 4.523 4.220
AN
M
Calc 3.790 3.764 3.897 3.804 3.741 3.761 3.758 4.097 3.997 3.706 4.339 4.502 4.313 4.718 4.585 4.573 4.395 4.434 4.404 4.416 4.016 4.168 4.406 4.573 4.251
PT
Solvent Hexane Heptane Octane Nonane Decane Dodecane Hexadecane Cyclohexane Methylcyclohexane 2,2,4-Trimethylpentane Tetrachloromethane 1,2-Dichloroethane 1-Chlorobutane Carbon disulfide Benzene Toluene Ethylbenzene o-Xylene m-Xylene p-Xylene Dibutylether Methyl tert-butylether 1,4-Dioxane Tetrahydrofuran Methyl acetate
CR
in mol dm
IP
Calculated and observed solubilities of ferrocene in solvents at 298 K, as log Ss with Ss
12
Obs -0.765 -0.772 -0.778 -0.789 -0.797 -0.823 -0.861 -0.521 -0.581 -0.880 -0.153 -0.031 -0.253 0.003 -0.059 -0.118 -0.206 -0.183 -0.222 -0.205 -0.518 -0.463 -0.013 -0.096 -0.399
ACCEPTED MANUSCRIPT 13
ED
CE
AC
T
-0.367 -0.376 -0.511 -0.856 -0.705 -1.943 -0.432 -0.098 -0.996 -0.928 -1.038 -0.893 -0.956 -0.986 -1.012 -0.906 -0.939 -0.954 -0.849 -0.859 -0.941 -0.977 -0.839 -0.852 -0.974 -0.837 -1.928 -1.094 -1.504 -1.767 -2.082 -2.443 -2.820
IP
CR
-0.329 -0.335 -0.345 -0.781 -0.658 -2.223 -0.431 -0.135 -0.870 -0.904 -1.057 -0.871 -0.986 -1.008 -1.031 -0.825 -0.887 -0.929 -0.947 -0.824 -0.923 -0.997 -0.805 -0.824 -0.882 -0.827 -1.843 -1.024 -1.372 -1.721 -2.008 -2.439 -2.914
US
4.252 4.243 4.108 3.763 3.914 2.676 4.187 4.521 3.623 3.691 3.581 3.726 3.663 3.633 3.607 3.713 3.680 3.665 3.770 3.760 3.678 3.642 3.780 3.767 3.645 3.782 2.691 3.525 3.115 2.852 2.537 2.176 1.799
AN
M
4.290 4.284 4.274 3.838 3.961 2.396 4.188 4.484 3.749 3.715 3.562 3.748 3.633 3.611 3.588 3.794 3.732 3.690 3.672 3.795 3.696 3.622 3.814 3.795 3.737 3.792 2.776 3.595 3.247 2.898 2.611 2.180 1.705
PT
Ethyl acetate Butyl acetate Propanone Acetonitrile Dimethylsulfoxide Formamide Dimethylformamide Pyridine Ethanol Propan-1-ol Propan-2-ol Butan-1-ol Butan-2-ol 2-Methylpropan-1-ol 2-Methylpropan-2-ol Pentan-1-ol Pentan-2-ol 3-Methylbutan-1-ol 2-Methylbutan-2-ol Hexan-1-ol 2-Methylpentan-1-ol 4-Methylpentan-2-ol Heptan-1-ol Octan-1-ol 2-Ethylhexan-1-ol Decan-1-ol Ethylene glycol Methanol 80% vol Ethanol-water 70% vol Ethanol-water 60% vol Ethanol-water 50% vol Ethanol-water 40% vol Ethanol-water
Acetylferrocenes. Solubility data are available for acetylferrocene and 1,1’bis(acetyl)ferrocene (diacetylferrocene). Buryukin et al. [52] have determined the solubility of both compounds in water and in dimethylsulfoxide, Zakharenko et al. [53] have determined the solubility of both compounds over the full range of water-ethanol mixtures, and Matveev and Statsenko [8] had much earlier measured the solubility of 13
ACCEPTED MANUSCRIPT 14
both compounds in a range of solvents. Unfortunately, the three recorded solubilities in water for acetylferrocene are all different, values of log Sw being -2.32 [52], -1.491 [53] and -1.41 [8]. We therefore used only the solubility values of log Ss in water-ethanol mixtures [53], obtain the corresponding values of log Ps, as shown in Table 6, and then used the log Ps values in the usual way to obtain descriptors for acetylferrocene. These yielded 26 equations, and we had another two equations from an experimental value of
T
2.1 for log Ps into wet octanol [50], making a total of 28 equations. We took E = 1.537
IP
by addition of fragments and V = 1.5018 calculated as for ferrocene. Then analysis of the
CR
28 equations yielded the descriptors shown in Table 4 with an SD of 0.082 log units between calculated and observed values. The twelve calculated and observed values of
US
log Ps obtained from solubilities are in Table 6 and yield AE = 0.002, AAE = 0.040, RMSE = 0.047 and SD = 0.051. Exactly the same statistics will be found for the
AN
corresponding values of log Ss using log Sw = -1.49 [53].
M
Table 6
Calculated and observed values of log Ps for acetylferrocene and diacetylferrocene
Acetylferrocene Calc Obs 2.139 2.213 2.141 2.165 2.139 2.159 2.134 2.132 2.040 2.031 1.841 1.837 1.652 1.597 1.394 1.323 1.111 1.039 0.774 0.759 0.443 0.494 0.163 0.240
Diacetylferrocene Calc
Obs
AC
CE
PT
Solvent Ethanol 96% vol Ethanol-water 95% vol Ethanol-water 90% vol Ethanol-water 80% vol Ethanol-water 70% vol Ethanol-water 60% vol Ethanol-water 50% vol Ethanol-water 40% vol Ethanol-water 30% vol Ethanol-water 20% vol Ethanol-water 10% vol Ethanol-water
ED
at 298 K
14
1.770 1.785 1.681 1.511 1.320 1.103 0.795 0.486 0.208
1.715 1.663 1.651 1.564 1.396 1.165 0.894 0.606 0.304
ACCEPTED MANUSCRIPT 15
The discrepancies in solubilities noted for acetylferrocene are apparent also for diacetylferrocene. We deduced E = 1.680 by addition of fragments, and calculated V = 1.7993. We took the solubilities in water-ethanol mixtures [53] and obtained values of log Ps from log Sw = - 1.725. There are fewer data points than for acetylferrocene, and the fit is not so good. For 20 equations we obtained SD = 0.099 log units. The observed and calculated values of log Ps are in Table 6 and can be converted into corresponding
T
log Ss values through log Sw = -1.725. For the observed and calculated values AE =
IP
0.033, AAE = 0.079, RMSE = 0.085 and SD = 0.090 log units for the nine sets of data.
determined
for
both
acetoacetylferrocene
CR
Solubilities in water-methanol [54] and water-ethanol [55] mixtures have been and
1,1-bis(acetoacetyl)ferrocene,
US
diacetoacetylferrocene. In both cases, the solubility in water-methanol mixtures, and hence log P for water-methanol mixtures, was far larger than the corresponding values in
AN
water-ethanol mixtures, and far larger than we calculated by any reasonable set of descriptors. This is illustrated by the plots of log P for diacetoacetylferrocene shown in
M
Figure 1. Since the same group of workers carried out the solubility measurements in both aqueous alcohols, we rule out any experimental error and suggest that methanol
ED
could form solvates with both of the substituted ferrocenes. Vasiliev et al. [56] have determined the X-ray structure and also the NMR spectrum in deuterochloroform of
PT
diacetoacetylferrocene but neither of these studies leads to any indication of why methanol, specifically, could form solvates.
Using just the solubility data in water-
CE
ethanol mixtures, we obtained the descriptors shown in Table 4 for acetoacetylferrocene with SD = 0.050 for 26 equations, and SD = 0.138 for diacetoacetylferrocene from 18
AC
equations. A plot of observed and calculated log P values for the latter is in Figure 1. The descriptors for acetoacetylferrocene and diacetoacetylferrocene are based only on a restricted type of solvent, and we suggest should be taken as provisional only.
15
ACCEPTED MANUSCRIPT 16
4
T
2
IP
Log P
3
CR
1
10
20
30
40 50 Vol% alcohol
60
70
80
90
AN
0
US
0
M
Figure 1. Values of log Ps for diacetoacetylferrocene in aqueous alcohols: ○ Observed values in water-methanol, □ calculated values in water – methanol, ● observed values in
PT
ED
water- ethanol, ■ calculated values in water-ethanol
Other substituted ferrocenes. A certain amount of data is available for
CE
ferrocenylcarbinol, Ferr-CH2OH, ferrocenylmethylcarbinol,
Ferr-CH(Me)OH, and
ferrocenyldimethylcarbinol, Ferr-C(Me)2OH. Water-octanol partition coefficients are
AC
known for ferrocenylcarbinol, log Ps = 2.0 [50], and for ferrocenylmethylcarbinol, log Ps = 2.3 [50], and there have been studies on the solubility of ferrocenyldimethylcarbinol in various organic solvents [8] and in some water-ethanol mixtures [9], For these carbinols, there is the additional A-descriptor to determine. Only for ferrocenyldimethylcarbinol is there enough data to obtain all the required descriptors, but we found that the two sets of data [8, 9] were not internally compatible and we were unable to deduce any reasonable set of descriptors. We have values of E (Table 3) for alkylferrocenes, we can calculate V and we know that A = 0. We know also that values of S, B and especially L vary regularly along 16
ACCEPTED MANUSCRIPT 17
any homologous series [57, 58] and so we can estimate descriptors for alkylferrocenes by comparison with ferrocene itself and homologous series. We particularly used descriptors for cyclohexane and alkylcyclohexanes so that, for example L(alkylferrocene) = L(ferrocene) + L(alkylcyclohexane – L(cyclohexane). We were able to obtain a set of descriptors for simple alkylferrocenes in this way, as given in Table 4. The descriptors
T
form a coherent series, as shown by the regular change in log Kw with the alkyl group.
IP
4. Conclusions
CR
We have shown that exactly the same methods that we have used to obtain Abraham (Absolv) descriptors for a variety of organic compounds can be applied to a series of
US
substituted ferrocenes. However, there were difficulties in the assignment of the E and V descriptors that had to be overcome when dealing with these compounds that contained
AN
an iron atom, and we envisage similar difficulties in the determination of descriptors for compounds such as inorganic complexes. Once the difficulties over E and V are
M
overcome, it is apparent that substituted ferrocenes can be dealt with in exactly the same way as typical organic compounds, with substituent effects falling into similar patterns.
ED
The descriptors for ferrocene and substituted ferrocenes can be used to estimate log Ps values for partition into a very large number of organic and aqueous organic phases,
PT
see Table 1. These estimated log Ps values can in turn be used to obtain the corresponding solubilities through Eq. 3 provided that the water solubility, as log Ss is
AC
Funding
CE
known.
This research received no grants from any funding agencies in the public, commercial, or not-for-profit sectors.
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T
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IP
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ED
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AC
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physicochemical and biochemical processes, Chem. Soc. Revs. 22 (1993) 73-83. [14] M. H. Abraham, A. Ibrahim, A. M. Zissimos, The determination of sets of solute descriptors from chromatographic measurements, J. Chromatogr.A 1037 (2004) 29-47.
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CR
properties of compounds from chromatographic measurements and the solvation parameter model, J. Chromatogr. A 1317 (2013) 85-104.
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[17] E. D. Clarke and L. Mallon, “The Determination of Abraham descriptors and their Application to Crop Protection Research”, in Modern Methods in Crop Protection
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Sci. 99 (2010) 1500-1515.
ED
Jr., Prediction of solubility of drugs and other compounds in organic solvents, J. Pharm.
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[19] M. H. Abraham, W. E. Acree, Jr., A. J. Leo, D. Hoekman, The partition of
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compounds from water and from air into wet and dry ketones, New J. Chem. 33 (2009)
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AC
H. Abraham, Mathematical correlations for describing solute transfer into functionalized alkane solvents containing hydroxyl, ether, ester or ketone solvents, Fluid Phase Equilib. 298 (2010) 48-53.
[21] M. H. Abraham and W. E. Acree, Jr., The transfer of neutral molecules, ions and ionic species from water to ethylene glycol and to propylene carbonate; descriptors for pyridinium cations, New J. Chem. 34 (2010) 2298-2305. [22] M. H. Abraham and W. E. Acree, Jr., The transfer of neutral molecules, ions and ionic species from water to wet octanol, Phys. Chem. Chem. Phys. 12 (2010) 1318213188 19
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[23] M. H. Abraham and W. E. Acree, Jr., Partition coefficients and solubilities of compounds in the water-ethanol solvent system, J. Soln. Chem. 40 (2011) 1279-1290. [24] T. W. Stephens, N. E. De La Rosa, M. Saifullah, S. Ye, V. Chou, A. N. Quay, W.E.Acree, Jr. and M. H. Abraham, Abraham model correlations for solute partitioning into o-xylene, m-xylene and p-xylene from both water and the gas phase, Fluid Phase Equilib. 308 (2011) 64-71.
T
[25] T. W. Stephens, N. E. De La Rosa, M. Saifullah, S. Ye, V. Chou, A. N. Quay, W. E.
IP
Acree, Jr. and M. H. Abraham, Abraham model correlations for transfer of neutral
CR
molecules and ions to sulfolane, Fluid Phase Equilib. 309 (2011) 30-35. [26] T. W. Stephens, A. N. Quay, V. Chou, M. Loera, C. Shen, A. Wilson, W. E. Acree,
US
Jr. and M. H. Abraham, Correlation of solute transfer into alkane solvents from water and from the gas phase with updated Abraham model equations, Global J. Phys. Chem. 3
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(2012) 1-42.
[27] M. H. Abraham and W. E. Acree, Jr., The transfer of neutral molecules, ions and
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ionic species from water to benzonitrile; comparison with nitrobenzene, Thermochim. Acta 526 (2011) 22-28.
ED
[28] M. Saifullah, S. Ye, L. M. Grubbs, N. E. De La Rosa, W. E. Acree, Jr. and M. H. Abraham, Abraham model correlations for the transfer of neutral molecules to
PT
tetrahydrofuran and to 1,4-dioxane and for transfer of ions to tetrahydrofuran, J. Soln. Chem. 40 (2011) 2082-2094.
CE
[29] T. W. Stephens, M. Loera, A. N. Quay, V. Chou, C. Shen, A. Wilson, W. E. Acree, Jr. and M. H. Abraham, Correlation of solute transfer into toluene and ethylbenzene from
AC
water and from the gas phase based on the Abraham model, Open Thermodyn. J. 5 (2011) 104-121.
[30] T. W. Stephens, A. Wilson, N. Dabadge, A. Tian, H. J. Hensley, M. Zimmerman, W. E. Acree, Jr. and M. H. Abraham, Correlation of solute partitioning into isooctane from water and from the gas phase based on updated Abraham equations, Global J. Phys. Chem. 3 (2012) 9 [31] M. H. Abraham and W. E. Acree, Jr., Equations for the partition of neutral molecules, ions and ionic species from water to water-ethanol mixtures, J. Soln. Chem. 41 (2012) 730-740. 20
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[32] M. Brumfield, W. E. Acree Jr. and M. H. Abraham, Abraham model correlations for describing solute transfer into diisopropyl ether, Phys. Chem. Liq. 53 (2015) 25-37. [33] M. Brumfield, A. Wadawadigi, N. Kuprasertkul, S. Mehta, W. E. Acree Jr. and M. H. Abraham, Abraham model correlations for solute transfer into tributyl phosphate from both water and the gas phase, Phys. Chem. Liq. 53 (2015) 10-24.
T
[34] I. A. Sedov, M. A. Stolov, E. Hart, D. Grover, H. Zetti, V. Koshevarova, C. Dai, S.
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Zhang, W. E. Acree, Jr., and M. H. Abraham, Abraham model correlations for describing
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solute transfer into 2-butoxyethanol from both water and the gas phase at 298K, J. Mol. Liq. 209 (2015) 196-202.
[35] E. Hart, D. Grover, H. Zettl, V. Koshevarova, S. Zhang, C. Dai, W. E. Acree, Jr., I.
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A. Sedov, M. A. Stolov, and M. H. Abraham, Abraham model correlations for solute transfer into 2-methoxyethanol from water and from the gas phase, J. Mol. Liq. 209
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(2015) 738-744.
[36] M. H. Abraham, M. Zad and W. E. Acree, Jr., The transfer of neutral molecules
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from water and from the gas phase to solvents acetophenone and aniline, J. Mol. Liq. 212
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(2015) 301-306.
[37] D. M. Stovall, A. Schmidt, C. Dai, S. Zhang, W. E. Acree Jr. and M. H. Abraham, Abraham model correlations for estimating solute transfer of neutral compounds into
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anhydrous acetic acid from water and from the gas phase, J. Mol. Liq. 212 (2015) 16-22. [38] I. A. Sedov, D. Khaibrakhmanova, E. Hart, D. Grover, H. Zetti, V. Koshevarova, C.
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Dai, S. Zhang, A. Schmidt, W. E. Acree, Jr., and M. H. Abraham, Development of Abraham model correlations for solute transfer into both 2-propoxyethanol and 2-
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isopropoxyethanol at 298.15 K, J. Mol. Liq. 212 (2015) 833-840. [39] M. H. Abraham and W. E. Acree, Jr., Equations for the partition of neutral molecules, ions and ionic species from water to water-methanol mixtures. J. Soln. Chem. 45 (2016) 861-874 [40] W. E. Acree Jr., M. Y. Horton, E. Higgins and M. H. Abraham, Abraham model linear free energy relationships as a means of extending solubility studies to include the estimation of solute solubilities in additional organic solvents, J. Chem. Thermodynam. 102 (2016) 392-397.
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[41] I. A. Sedov, T. Salikov, E. Hart, E. Higgins, W. E. Acree Jr. and M. H. Abraham, Abraham model linear free energy relationships for describing the partitioning and solubility behaviour of nonelectrolyte organic solutes dissolved in pyridine at 298.15 K, Fluid Phase Eq. 431 (2017) 66-74. [42] M. H. Abraham and J. C. McGowan, The use of characteristic volumes to measure cavity terms in reversed-phase liquid chromatography. Chromatographia 23 (1987) 243-
T
246.
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[43] Y. H. Zhao, M. H. Abraham and A. M. Zissimos, Determination of McGowan
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volumes for ions and correlation with van der Waals volumes, J. Chem. Inf. Comput. Sci. 43 (2003) 1848-1854.
[45] American Chemical Society SciFinder.
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[44] D. Tran, J. P. Hunt and S. Wherland, Inorg. Chem. 31 (1992) 2460-2464.
AN
[46] M. Aroney, R. J. W. Le Fevre and K. M. Somasundaram, Molecular polarizability. The Molar Kerr constant of ferrocene, J. Chem. Soc. (1960) 1812- 1814. A. I. Nikitina, P. K. Leont’evskaya and A. A. Pendin, Selective solvation of
M
[47]
ferrocene, tetraphenylmethane and tetraphenylgermane in aqueous-aprotic solvents. Russ.
ED
J. Gen. Chem. 68 (1998) 697-703.
[48] BioLoom, BioByte Corp, 201 W. 4th Street, #204 Claremont, CA 91711-4707,
PT
USA. EPI Suite TM
[50]
A. J. Bergren and M. C. Porter, Selectivity mechanisms at self-assembled
CE
[49]
monolayers on gold: implications in redox recycling amplification systems, J.
AC
Electroanal. Chem. 599 (2007) 12-22. [51] ChemSketch. ACD Advanced Chemistry Development, 110 Yonge Street, 14th Floor, Toronto, Ontario, M5C 1T4, Canada. [52] F. A. Buryukin, V. P. Tverdokhlebov, V. A. Fedorov, E. V. Tetenkova, A. V. Fedorova and O. O. Azanova, The solubility of acetylferrocene and diacetylferrocene in dimethylsulfoxide and its mixtures with water, Russ. J. Phys. Chem. 82 (2008) 15451548.
22
ACCEPTED MANUSCRIPT 23
[53] A. V. Zakharenko, P. V. Fabinskii, O. M. Batalova, V. P. Tverdokhlebov and V. A. Fedorov, Solubility of acetyl- and diacetyl-ferrocene in mixed aqueous-alcoholic solvents. Russ. J. Gen. Chem. 73 (2003) 70-74. [54] E. E. Sergeev, P. V. Fabinskii and V. A. Fedorov, Temperature dependences of the solubility of acetoacetylferrocene and 1,1’-bis(acetoacetyl)ferrocene in water-methanol mixed solvents, Russ. J. Phys. Chem. 81 (2007) 1054-1058.
T
[55] E. E. Sergeev, P. V. Fabinskii, B. V. Polyakov and V. A. Fedorov. Thermodynamics
CR
ethanol, Russ. J. Phys. Chem. 51 (2006) 687-690.
IP
of the dissolution of acetoacetylferrocene and 1,1’-bis(acetoacetyl)ferrocene in aqueous
[56] A. D. Vasiliev, O. A. Bayukov, A. A. Kondrasenko, E. E. Sergeev, P. V. Fabinskiy
US
and V. A. Fedorov. Crystal and molecular structure of 1,1’-bis(acetoacetyl)ferrocene. J. Struct. Chem. 51 (2010) 114-119.
Toronto, Ontario, M5C 1T4, Canada.
AN
[57] Absolv. ACD Advanced Chemistry Development, 110 Yonge Street, 14th Floor,
M
[58] UFZ-LSER data base: S.Endo, T. N. Brown, N. Watanabe, N. Ulrich, G., Bronner,
ED
M. H. Abraham and K.-U. Goss, : UFZ-LSER database v 3.1 [Internet], Leipzig, Germany, Helmholtz Centre for Environmental Research-UFZ. 2015. Available from
AC
Bullet points
CE
PT
w.ufz.de/lserd http://www.ufz.de/lserd.
Solubilities of ferrocene in 58 solvents examined Abraham descriptors for ferrocene and substituted ferrocenes determined Ferrocene is hydrophobic, with no acidity, little basicity but with moderate dipolarity Solubilities and partition properties of the ferrocenes can be estimated
Cover letter
23
ACCEPTED MANUSCRIPT 24
We have compiled a list of solubilities of ferrocene in 58 solvents, and used these to obtain the corresponding water-solvent partition coefficients. From the latter, we have obtained Abraham descriptors and can use these to estimate water-solvent partition coefficients and solubilities of ferrocene in a large number of other solvents. The descriptors show that ferrocene is hydrophobic, with no hydrogen bond acidity, little hydrogen bond basicity, but with a significant dipolarity. Descriptors for a number of
T
substituted ferrocenes have also been obtained. It is thus shown that our general method
IP
for determination of descriptors for organic compounds is applicable to the set of
CR
ferrocenes, and that in principle descriptors can be obtained for any substituted ferrocene. Furthermore, the analysis we have made on ferrocene descriptors will enable descriptors
US
to be obtained for cyclopentadiene derivatives of other transition metals. This greatly enlarges the scope of our descriptor method and should be of interest to all those
AN
interested in physicochemical properties of organic compounds and, now, organic
AC
CE
PT
ED
M
compounds of transition elements.
24
Michael H. Abraham, William E. Acree PII: DOI: Reference:
S0167-7322(16)34299-4 doi: 10.1016/j.molliq.2017.02.059 MOLLIQ 6972
To appear in:
Journal of Molecular Liquids
Received date: Revised date: Accepted date:
1 January 2017 13 February 2017 15 February 2017
Please cite this article as: Michael H. Abraham, William E. Acree , Descriptors for ferrocene and some substituted ferrocenes. The address for the corresponding author was captured as affiliation for all authors. Please check if appropriate. Molliq(2017), doi: 10.1016/j.molliq.2017.02.059
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ACCEPTED MANUSCRIPT 1
Descriptors for ferrocene and some substituted ferrocenes
and William E. Acree, Jr
b
IP
c
a*
T
Michael H Abraham
Department of Chemistry, 1155 Union Circle Drive #305070, University of North
CR
Texas, Denton, TX 76203-5017, USA Email: [email protected]
US
Keywords: ferrocene, acetylferrocene, acetoacetylferrocene, gas-solvent partition coefficients, water-solvent partition coefficients, solubility, linear free energy
AN
relationships
M
ABSTRACT
We have used literature data on solubilities in 58 solvents to obtain Abraham (Absolv)
ED
descriptors for ferrocene. The required descriptor E was obtained through known measurements of molar refraction, and the V descriptor was obtained through comparison
PT
of partial molal volumes with McGowan volumes, Vx, for 58 compounds. Ferrocene is quite hydrophobic, with our calculated water-octanol partition coefficient as 3.70 ( log
CE
Ps), it has no hydrogen bond acidity, only a small hydrogen bond basicity, but a significant dipolarity. Descriptors for a number of derivatives of ferrocene were also
AC
obtained from solubility data; these derivatives were acetylferrocene, diacetylferrocene, acetoacetylferrcene
and
diacetoacetylferocene.
In
addition,
descriptors
for
alkylferrocenes were estimated by comparison. Substituent effects on ferrocene are very similar to substituent effects on purely organic compounds, and could be used to estimate descriptors for a variety of monosubstituted ferrocenes.
* Corresponding author. Tel.: 020-7679-4639; fax: 020-7679-7463. E-mail address: [email protected] (M. H. Abraham) 1
ACCEPTED MANUSCRIPT 2
1. Introduction There is considerable recent interest in ferrocene and its derivatives, especially with regard to nonlinear optical processes [1, 2], and there have been several new solubility
T
studies, especially by De Fina et al. [3] who compared observed solubilities with those
IP
predicted by mobile order theory. We have previously determined Abraham (or Absolv)
CR
descriptors for ferrocene [4], using a very restricted data set, but there is now much more solubility data available [3, 5, 6] and we have also been able to set out general methods
US
for the calculation of some of the descriptors. Our aim was therefore to use all this recent data on ferrocene [5-12] to obtain more reliable descriptors for ferrocene, and then for
AN
some of its derivatives. 2. Methodology
M
Our method is based on two general linear free energy relationships, Eqs. (1) and (2), that can be used to correlate and to predict the transfer of neutral solutes from water
ED
to organic solvents and from the gas phase to organic solvents. The dependent variable in Eq. (1) is log P, where P is the molar water to solvent partition coefficient for a series of
PT
solutes, and in Eq. (2) is log K where K is the dimensionless gas phase to solvent partition coefficient for a series of solutes [13-17]. The general method has been reviewed several
CE
times [13-17]; the review by Clarke and Mallon [17] is particularly comprehensive.
(1)
AC
Log P = c + e E + s S + a A + b B + v V Log K = c + e E + s S + a A + b B + l L
(2)
In Eq. (1) and (2) the independent variables, or descriptors, are properties of the neutral solutes as follows [13-17]: E is the solute excess molar refraction in cm3 mol-1/10, S is the solute dipolarity/polarizability, A is the overall solute hydrogen bond acidity, B is the overall solute hydrogen bond basicity, V is McGowan’s characteristic molecular volume in cm3 mol-1/100 and L is the logarithm of the gas to hexadecane partition coefficient at
2
ACCEPTED MANUSCRIPT 3
298 K. The coefficients in Eq. 1 and Eq. 2 are shown in Table 1 for partition from water to the various solvents that we shall encounter [18 - 41].
Table 1. Coefficients in Eq. (1) and Eq. (2) for partitions from water and from the gas phase to
0.560 0.670 0.642 0.619 0.585 0.668 0.667 0.784 0.782 0.555
Trichloromethane Tetrachloromethane 1,2-Dichloroethane
0.191 0.199 0.183
-1.710 -2.061 -1.647 -1.713 -1.734 -1.644 -1.617 -1.678 -1.982 -1.737
a
b
v
-3.578 -3.317 -3.480 -3.532 -3.435 -3.545 -3.587 -3.740 -3.517 -3.677
-4.939 -4.733 -5.067 -4.921 -5.078 -5.006 -4.869 -4.929 -4.293 -4.864
4.463 4.543 4.526 4.482 4.582 4.459 4.433 4.577 4.528 4.417
CR
Heptane Octane Nonane Decane Dodecane Hexadecane Cyclohexane Methylcyclohexane 2,2,4-Trimethylpentane
0.333 0.325 0.223 0.240 0.160 0.114 0.087 0.159 0.246 0.318
Hexane
s
US
e
AN
c
M
Solvent, Eq. 1
IP
T
various solvents.
-0.403 -1.159 -0.134
-3.112 -3.560 -2.801
-3.514 -4.594 -4.291
4.395 4.618 4.180
0.222
0.273
-0.569
-2.918
-4.883
4.456
0.047
0.686
-0.943
-3.603
-5.818
4.921
0.142
0.464
-0.588
-3.099
-4.625
4.491
Toluene Ethylbenzene
0.143 0.093
0.527 0.467
-0.720 -0.723
-3.010 -3.001
-4.824 -4.844
4.545 4.514
o-Xylene
0.083
0.518
-0.813
-2.884
-4.821
4.559
m-Xylene
0.122
0.377
-0.603
-2.981
-4.961
4.535
p-Xylene
0.166
0.477
-0.812
-2.939
-4.874
4.532
Dibutylether Methyl tert-butylether
0.203 0.341
0.369 0.307
-0.954 -0.817
-1.488 -0.618
-5.426 -5.097
4.508 4.425
1,4-Dioxane
0.098
0.350
-0.083
-0.556
-4.826
4.172
Tetrahydrofuran
0.207
0.372
-0.392
-0.236
-4.934
4.447
AC
Benzene
CE
Carbon disulfide
PT
1-Chlorobutane
ED
0.105 0.523 0.294
3
ACCEPTED MANUSCRIPT 0.351
0.223
-0.150
-1.035
-4.527
3.972
Ethyl acetate
0.328
0.369
-0.446
-0.700
-4.904
4.150
Butyl acetate
0.248
0.356
-0.501
-0.867
-4.973
4.281
Propanone
0.313
0.312
-0.121
-0.608
-4.753
3.942
Acetonitrile
0.413
0.077
0.326
-1.566
-4.391
3.364
Dimethylsulfoxide
-0.194
0.327
0.791
1.260
-4.540
3.361
Formamide
-0.171
0.070
0.308
0.589
T
2.432
Dimethylformamide
-0.305
-0.058
0.343
0.358
-4.865
4.486
Pyridine
-0.046
0.298
0.000
0.558
4.292
Ethanol Propan-1-ol
0.222 0.148
0.471 0.436
-1.035 -1.098
CR
-4.504
0.326 0.389
3.857 4.036
Propan-2-ol
0.102
0.315
-1.020
0.532
-3.865
4.023
Butan-1-ol
0.152
0.438
US
-3.596 -3.893
-1.177
0.096
-3.919
4.122
Butan-2-ol
0.194
0.383
-0.956
0.134
-3.606
3.829
2-Methylpropan-1-ol
0.161
0.310
-1.069
0.183
-3.774
4.040
2-Methylpropan-2-ol
0.211
0.171
-0.947
0.331
-4.085
4.109
Pentan-1-ol
0.150
0.536
-1.229
0.141
-3.864
4.077
0.115
0.455
-1.331
0.206
-3.745
4.201
0.073
0.360
-1.273
0.090
-3.770
4.273
0.177
0.316
-1.125
0.306
-4.112
4.178
0.115
0.492
-1.164
0.054
-3.978
4.131
2-Methylpentan-1-ol
0.074
0.423
-1.228
0.143
-4.031
4.221
4-Methylpentan-2-ol
0.055
0.369
-1.340
0.211
-4.035
4.322
Heptan-1-ol
0.035
0.398
-1.063
0.002
-4.342
4.317
Octan-1-ol
-0.034
0.489
-1.044
-0.024
-4.235
4.218
0.061
0.459
-1.067
-0.178
-4.117
4.120
Decan-1-ol
-0.058
0.616
-1.319
0.026
-4.153
4.279
Ethylene glycol
-0.243
0.695
-0.670
0.726
-2.399
2.670
Wet octan-1-ol
0.088
0.562
-1.054
0.034
-3.460
Methanol
0.276
0.334
-0.714
0.243
-3.320
3.814 3.549
AC
Hexan-1-ol
ED
CE
2-Methylbutan-2-ol
PT
Pentan-2-ol 3-Methylbutan-1-ol
2-Ethylhexan-1-ol
a
AN
Methyl acetate
M
4
4
IP
-3.152
ACCEPTED MANUSCRIPT 5
Solvent Eq. 2
c
e
Hexane
0.320
0.000
Heptane
0.275
-0.162
Octane
0.215
Nonane
0.200
Decane
0.156
0.297 0.294 0.262 0.260 0.311 0.293 0.251 0.171 0.260 0.096 0.065 3.813
3.724 3.697 3.545 -3.212 -2.936 -2.675 -2.275 -1.809 -3.212 0.916 0.454 4.841
3.637 3.609 3.483 3.323 3.102 3.812 2.415 1.918 3.323 0.681 0.254 -0.869
T
-0.833 -0.795 -0.575 -0.465 -0.368 -0.335 -0.252 -0.159 -0.465 -0.040 -0.001 2.549
IP
0.353 0.328 0.213 0.175 0.085 0.138 0.124 0.131 0.175 0.042 -0.023 0.577
CR
0.238 0.239 0.243 0.172 0.063 -0.040 -0.142 -0.221 0.172 -0.252 -0.173 -0.994
s
a
b
l
0.000
0.000
0.000
0.945
0.000
0.000
0.000
0.983
-0.049
0.000
0.000
0.000
0.967
-0.145
0.000
0.000
0.000
0.980
-0.143
0.000
0.000
0.000
0.989
0.017
0.000
0.000
0.000
0.000
0.989
0.000
0.000
0.000
0.000
0.000
1.000
0.163
-0.110
0.000
0.000
0.000
1.013
0.318
-0.215
0.000
0.000
0.000
1.012
2,2,4-Trimethylpentane
0.264
-0.230
0.000
0.000
0.000
0.975
Trichloromethane
0.157
-0.560
1.259
0.374
1.333
0.976
AC
ED
M
AN
US
96% vol Ethanol-water 95% vol Ethanol-water 90% vol Ethanol-water 80% vol Ethanol-water 70% vol Ethanol-water 60% vol Ethanol-water 50% vol Ethanol-water 40% vol Ethanol-water 30% vol Ethanol-water 20% vol Ethanol-water 10% vol Ethanol-water Gas to water
Tetrachloromethane
0.217
-0.435
0.554
0.000
0.000
1.069
1,2-Dichloroethane
0.017
-0.337
1.600
0.774
0.637
0.921
1-Chlorobutane
0.130
-0.581
1.114
0.724
0.000
1.016
Carbon disulfide
0.101
0.251
0.177
0.027
0.095
1.068
Benzene
0.107
-0.313
1.053
0.457
0.169
1.020
Toluene
0.121
-0.222
0.938
0.467
0.099
1.012
Ethylbenzene
0.059
-0.295
0.924
0.573
0.098
1.010
o-Xylene
0.064
-0.296
0.934
0.647
0.000
1.010
Dodecane
Cyclohexane
CE
Methylcyclohexane
PT
Hexadecane
5
ACCEPTED MANUSCRIPT 0.071
-0.423
1.068
0.552
0.000
1.014
p-Xylene Dibutylether
0.113 0.165
-0.302 -0.421
0.826 0.760
0.651 2.102
0.000 -0.664
1.011 1.002
Methyl tert-butylether
0.278
-0.489
0.801
2.495
0.000
0.993
1,4-Dioxane
-0.034
-0.354
1.674
3.021
0.000
0.919
Tetrahydrofuran
0.189
-0.347
1.238
3.289
0.000
0.982
Methyl acetate
0.134
-0.477
1.749
2.678
T
0.876
Ethyl acetate
0.182
-0.352
1.316
2.891
0.000
0.916
Butyl acetate
0.147
-0.414
1.212
2.623
0.954
Propanone
0.217
-0.387
1.733
3.060
0.000
0.866
Acetonitrile
-0.007
-0.595
2.461
CR
0.000
2.085
0.418
0.738
Dimethylsulfoxide
-0.556
-0.223
2.903
5.037
0.000
0.719
Formamide
-0.800
0.310
2.292
4.130
1.933
0.442
Dimethylformamide
-0.391
-0.869
2.107
3.774
0.000
1.011
Pyridine
-0.123
-0.588
1.991
4.363
0.000
0.942
Ethanol
0.017
0.867
3.894
1.192
0.846
Propan-2-ol
Butan-2-ol
CE
2-Methylpropan-1-ol 2-Methylpropan-2-ol
AC
Pentan-2-ol
3-Methylbutan-1-ol 2-Methylbutan-2-ol
M
IP
-0.246
0.749
3.888
1.076
0.874
-0.048
-0.324
0.713
4.036
1.055
0.884
-0.004 -0.017
-0.285 -0.376
0.768 0.852
3.705 3.740
0.879 1.161
0.890 0.867
0.012
-0.407
0.670
3.645
1.283
0.895
0.053
-0.443
0.699
4.026
0.882
0.907
-0.002
-0.161
0.535
3.778
0.960
0.900
-0.031
-0.325
0.496
3.792
1.024
0.934
-0.052
-0.430
0.628
3.661
0.932
0.937
0..014
-0.435
0.573
3.965
0.811
0.943
-0.014
-0.205
0.583
3.621
0.891
0.913
-0.061
-0.289
0.539
3.787
0.911
0.923
-0.047
-0.376
0.398
3.845
0.897
0.952
-0.056
-0.216
0.554
3.596
0.803
0.933
a
Hexan-1-ol 2-Methylpentan-1-ol
a
4-Methylpentan-2-ol
a
Heptan-1-ol
0.000
-0.042
PT
Butan-1-ol
Pentan-1-ol
-0.232
ED
Propan-1-ol
AN
m-Xylene
US
6
6
ACCEPTED MANUSCRIPT 7
Octan-1-ol
0.749
0.943
-0.085
-0.384
0.616
3.383
0.673
0.959
-0.139
-0.090
0.356
3.547
0.727
0.958
-0.887
0.132
1.657
4.457
2.355
0.565
-0.222 -0.039 -0.032 -0.040 -0.084 -0.253 -0.438 -0.631 -0.851 -1.074 -1.258 -1.364 -1.447 -1.271
0.088 -0.338 -0.181 -0.200 -0.280 -0.278 -0.255 -0.186 -0.063 0.075 0.194 0.383 0.446 0.822
0.701 1.317 0.980 1.024 1.180 1.400 1.548 1.646 1.806 2.076 2.300 2.385 2.536 2.743
3.473 3.826 3.940 3.950 3.959 4.000 4.040 4.054 4.050 4.020 4.000 3.950 3.905 3.904
1.477 1.396 1.379 1.400 1.474 1.775 2.074 2.355 2.745 3.196 3.713 4.280 4.750 4.814
0.851 0.773 0.802 0.795 0.757 0.715 0.659 0.584 0.479 0.347 0.206 0.065 -0.052 -0.213
b
T
96% vol Ethanol-water 95% vol Ethanol-water 90% vol Ethanol-water 80% vol Ethanol-water 70% vol Ethanol-water 60% vol Ethanol-water 50% vol Ethanol-water 40% vol Ethanol-water 30% vol Ethanol-water 20% vol Ethanol-water 10% vol Ethanol-water Gas to water
IP
Methanol
CR
Wet octan-1-ol
Coefficients for ethanol-water mixtures from this work, using data from
ED
b
3.507
US
Ethylene glycol
This work.
0.561
AN
Decan-1-ol
a
-0.214
M
2-Ethylhexan-1-ol
-0.147 a
PT
[23, 31]
CE
Most of the data we shall encounter is in the form of solubilities, Ss, in various solvents. These can be transformed into water to solvent partition coefficients through
AC
Eq. (3) where Sw is the solubility in water. Eq. (3) is valid only if no hydrate in water or solvate in the solvent is formed – that is the same species must be in equilibrium with water and the solvent. P = Ss/Sw or log P = log Ss – log Sw
(3)
Then values of P obtained from solubilities can then be transformed into corresponding gas to solvent partition coefficients, Ks, through Eq. (4), where Kw is the gas to water partition coefficient. 7
ACCEPTED MANUSCRIPT 8
Ks = P*Kw or log Ks = log P + log Kw
(4)
Once values of log P and log Ks are available for a given solute, a set of simultaneous equations can be set up and solved for the unknown descriptors E, S, A, B, V and L and the (usually) unknown value of log Kw. Sometimes the required value of log Sw in Eq. 3
T
may not be known, in which case it can be treated as another unknown to be obtained
IP
through solution of the simultaneous equations. The ‘Solver’ add-on to the Microsoft
CR
Excel program provides a particularly convenient method for the solution of these simultaneous equations. Since the number of equations is always larger than the number
US
of unknowns, a trial-and-error procedure is adopted to obtain the unknowns that give the best-fit to the equations.
AN
It is a considerable advantage to be able to deduce the value of some of the descriptors, and hence to reduce the number of unknowns. For neutral organic
M
compounds, the McGowan volume, Vx [42], can be calculated from the McGowan atomic fragments, shown in Table 2 [42, 43], together with the subtraction of 6.56 cm -1
for any bond in the molecule, single, double and triple bonds all being counted as
ED
mol
3
the same. This is straightforward for organic molecules but in the case of ferrocene it is
PT
not clear how many ‘McGowan’ bonds there are. Each cyclopentadienyl entity has 10 bonds, making a total of 20, but an extra two bonds between the cyclopentadienyl groups
CE
and the iron atom may be counted, making 22 bonds in all. Calculations of Vx will then be Vx = 10*8.71 + 10*16.35 + 1.03 – 20 *6.56* = 120.43 or Vx = 10*8.71 + 10*16.35 3
-1
AC
+ 1.03 – 22 *6.56* = 107.31 cm mol . Tran et al. [44] have determined partial molal volumes in acetonitrile, Vm, for ferrocene and a large number of other compounds for which we can calculate Vx. There is a good correlation between the two sets of volumes shown in Eq. 5 and Eq. 6, where we forced the plot through the origin. N is the number of compounds, SD the standard deviation, R the correlation coefficient and F is the F2
statistic. PRESS and Q are the leave-one-out statistics and PSD is the predicted standard deviation.
8
ACCEPTED MANUSCRIPT 9
Vx = -10.237 + 0.9482 Vm
(5)
2
2
N = 58, SD = 6.05, R = 0.993, F = 7531.6, PRESS = 2181.40, Q = 0.992, PSD = 6.24
Vx = 0.8895 Vm
(6)
T
N = 58, SD = 7.74, PRESS = 3534.0, PSD = 7.87
AN
US
CR
IP
With Vm = 141.9 [44], Vx = 124.3 ± 6.2 from Eq. 5 or 126.2 ± 7.9 from Eq. 6, in reasonable agreement with Vx = 120.43 by the McGowan method with 20 bonds. We can then use the McGowan method to calculate Vx for any ferrocene, noting that there are no bonds between the cyclopentadienyl groups and the iron atom. Previously [4] we took Vx for ferrocene as 112.1 but the present value of 120.43 is much to be preferred.
Ge 31.02 Sn 39.35
P
24.87
As 29.42
O 12.43
ED
Si 26.83
N 14.39
S
22.91
Sb 37.74
Se 27.81
Br 26.21
Te 36.14
I
34.53
Fe
2+
1.03
Fe
3+
0.78
Co
3+
0.78
Cr
3+
1.08
CE
Pb 43.44
F 10.48 Cl 20.95
PT
H 8.71 C 16.35
M
Table 2 3 -1 Atomic volumes, Vx, in cm mol
o
The E-descriptor can be calculated from a liquid refractive index, η, at 20 C and a
AC
value of V (= Vx/100). Experimental values of η for some alkylferrocenes are available [45], and if V is calculated in the same way as for ferrocene, values of E are obtained as shown in Table 3. There is a good plot of E versus the number of carbon atoms and this was used to smooth the values – the taken values are in column 3. For ferrocene itself, 3
Aroney et al. [46] determined the molar refraction as 50.4 cm from which we can deduce that η = 1.629 whence E = 1.394, in good agreement with values for the alkylferrocenes.
9
ACCEPTED MANUSCRIPT 10
Table 3 Values of the E-descriptor for ferrocene and some alkylferrocenes
Ferrocene
1.394
E taken
a
1.394
1.409
Propylferrocene
1.393
1.393
Butylferrocene
1.320
1.373
Pentylferrocene
1.392
1.366
Diethylferrocene
1.373
1.373
CR
1.409
AN
Ethylferrocene
See text.
3. Results and discussion
ED
M
a
1.394
US
Methylferrocene
T
E from exp η
IP
Compound
Ferrocene. By far the largest data set on experimental solubilities of ferrocene is
PT
that of De Fina et al. [3]. A number of other workers [8, 12] have recorded solubilities in a few of the same solvents as used by De Fina et al. [3], but we just used the De Fina data
CE
for consistency. Solubilities are available in a number of solvents not studied by De Fina et al., viz: dodecane and trichloromethane [4], formamide [7], tetrahydrofuran and
AC
dimethylformamide [47] and some water-ethanol mixtures [9]. We did not use the solubility in trichloromethane [4], which was very much larger than calculated ( log Ss obs = 0.373, log Ss calc = -0.177). It is possible that trichloromethane forms a solvate with ferrocene. Fedorov et al. [5] determined the solubility of ferrocene in watermethanol mixtures, but their given solubilities in water and methanol are so different to other recorded solubilities, and to our calculated solubilities, that we did not use any of their data. We were left with solubilities in 58 solvents, that could be transformed into 58 log Ps and 58 log Ks values through Eq. 3 and Eq. 4. These yield 116 equations, and with 10
ACCEPTED MANUSCRIPT 11
two extra equations in log Kw we have a total of 118 equations from which to derive descriptors. These 118 equations were solved with SD = 0.077 log units, to give the descriptors in Table 4.The value of 2.12 for log Kw is in good agreement with an observed value of 2.00 [4], and our value of -4.619 for log Sw is in reasonable agreement with various recorded experimental values [4], viz: - 4.47, - 4.37, - 4.30 and - 4.17). Apart from the B (and A) descriptor, those for ferrocene are not particularly close to
T
those for two cyclopenta-1,3-diene molecules, see Table 4. There is really no other
CR
IP
molecule with which to compare descriptors.
Table 4
E
Cyclopentadiene
0.417
0.35
Ferrocene
1.394
0.90
Acetylferrocene
1.537
1.56
Diacetylferrocene
1.680
2.70
Acetoacetylferrocene
1.804
Diacetoacetylferrocene 2.214
A
B
0.00
V
0.12
Log Kw
L
0.6185
2.222
1.2043
6.003
2.12
-4.62
0.00
0.83 1.5018
7.861
6.56
-1.49
0.00
1.06 1.7993 10.170
10.39
-1.72
1.83
0.00
0.95 1.7993
9.595
7.75
-3.72
2.88
0.00
1.64 2.3943 13.146
13.67
-3.78
ED
M
0.23
0.00
0.25
1.3452 6.424
2.137
1.409 0.89
0.00
0.25
1.4861 6.899
2.035
1.393 0.90
0.00
0.25
1.6270 7.380
1.936
Butylferrocene
1.373 0.89
0.00
0.25
1.7679 7.850
1.784
Pentylferrocene
1.366 0.90
0.00
0.25
1.9088 8.376
1.695
Ethylferrocene
1.394 0.89
AC
CE
Propylferrocene
Log Sw
0.00
PT
Methylferrocene
S
AN
Compound
US
Calculated descriptors for ferrocene and substituted ferrocenes
We can compare calculated and observed log Ps and log Ss for the various solvents we have used, noting that log Ss (calc) = log Ps (calc) – 4.619. For the 58 calculated and observed values in Table 5, the average error, AE, = 0.002, the absolute average error, AAE = 0.056, the root mean square error, RMSE = 0.0758 and SD = 0.0764 log units, so that our method gives a good account of the solubility of ferrocene in a large range of solvents. Predictions of log Ps and log Ss can be made for any other solvent for which we have coefficients. Our calculated value of log Ps for partition into wet octanol is 3.70 as 11
ACCEPTED MANUSCRIPT 12
compared to other calculated values of 1.78 [48] and 3.28 [49], and an experimental value of 3.5 [50]. Thus ferrocene is quite hydrophobic, with a reasonably large value of log Ps into octanol. Ferrocene has zero hydrogen bond acidity and only a small hydrogen bond basicity. It does have, however, a substantial dipolarity, with S = 0.90. Note that the ACD ChemSketch program [51] cannot calculate log Ps for ferrocene.
T
Table 5 -3
Log Ps
ED
CE
AC
Log Ss
Calc -0.829 -0.855 -0.722 -0.815 -0.878 -0.858 -0.861 -0.522 -0.622 -0.913 -0.280 -0.117 -0.306 0.099 -0.034 -0.046 -0.224 -0.185 -0.215 -0.203 -0.603 -0.451 -0.213 -0.046 -0.368
US
Obs 3.854 3.847 3.841 3.830 3.822 3.796 3.758 4.098 4.038 3.739 4.466 4.588 4.366 4.622 4.560 4.501 4.413 4.436 4.397 4.414 4.101 4.156 4.606 4.523 4.220
AN
M
Calc 3.790 3.764 3.897 3.804 3.741 3.761 3.758 4.097 3.997 3.706 4.339 4.502 4.313 4.718 4.585 4.573 4.395 4.434 4.404 4.416 4.016 4.168 4.406 4.573 4.251
PT
Solvent Hexane Heptane Octane Nonane Decane Dodecane Hexadecane Cyclohexane Methylcyclohexane 2,2,4-Trimethylpentane Tetrachloromethane 1,2-Dichloroethane 1-Chlorobutane Carbon disulfide Benzene Toluene Ethylbenzene o-Xylene m-Xylene p-Xylene Dibutylether Methyl tert-butylether 1,4-Dioxane Tetrahydrofuran Methyl acetate
CR
in mol dm
IP
Calculated and observed solubilities of ferrocene in solvents at 298 K, as log Ss with Ss
12
Obs -0.765 -0.772 -0.778 -0.789 -0.797 -0.823 -0.861 -0.521 -0.581 -0.880 -0.153 -0.031 -0.253 0.003 -0.059 -0.118 -0.206 -0.183 -0.222 -0.205 -0.518 -0.463 -0.013 -0.096 -0.399
ACCEPTED MANUSCRIPT 13
ED
CE
AC
T
-0.367 -0.376 -0.511 -0.856 -0.705 -1.943 -0.432 -0.098 -0.996 -0.928 -1.038 -0.893 -0.956 -0.986 -1.012 -0.906 -0.939 -0.954 -0.849 -0.859 -0.941 -0.977 -0.839 -0.852 -0.974 -0.837 -1.928 -1.094 -1.504 -1.767 -2.082 -2.443 -2.820
IP
CR
-0.329 -0.335 -0.345 -0.781 -0.658 -2.223 -0.431 -0.135 -0.870 -0.904 -1.057 -0.871 -0.986 -1.008 -1.031 -0.825 -0.887 -0.929 -0.947 -0.824 -0.923 -0.997 -0.805 -0.824 -0.882 -0.827 -1.843 -1.024 -1.372 -1.721 -2.008 -2.439 -2.914
US
4.252 4.243 4.108 3.763 3.914 2.676 4.187 4.521 3.623 3.691 3.581 3.726 3.663 3.633 3.607 3.713 3.680 3.665 3.770 3.760 3.678 3.642 3.780 3.767 3.645 3.782 2.691 3.525 3.115 2.852 2.537 2.176 1.799
AN
M
4.290 4.284 4.274 3.838 3.961 2.396 4.188 4.484 3.749 3.715 3.562 3.748 3.633 3.611 3.588 3.794 3.732 3.690 3.672 3.795 3.696 3.622 3.814 3.795 3.737 3.792 2.776 3.595 3.247 2.898 2.611 2.180 1.705
PT
Ethyl acetate Butyl acetate Propanone Acetonitrile Dimethylsulfoxide Formamide Dimethylformamide Pyridine Ethanol Propan-1-ol Propan-2-ol Butan-1-ol Butan-2-ol 2-Methylpropan-1-ol 2-Methylpropan-2-ol Pentan-1-ol Pentan-2-ol 3-Methylbutan-1-ol 2-Methylbutan-2-ol Hexan-1-ol 2-Methylpentan-1-ol 4-Methylpentan-2-ol Heptan-1-ol Octan-1-ol 2-Ethylhexan-1-ol Decan-1-ol Ethylene glycol Methanol 80% vol Ethanol-water 70% vol Ethanol-water 60% vol Ethanol-water 50% vol Ethanol-water 40% vol Ethanol-water
Acetylferrocenes. Solubility data are available for acetylferrocene and 1,1’bis(acetyl)ferrocene (diacetylferrocene). Buryukin et al. [52] have determined the solubility of both compounds in water and in dimethylsulfoxide, Zakharenko et al. [53] have determined the solubility of both compounds over the full range of water-ethanol mixtures, and Matveev and Statsenko [8] had much earlier measured the solubility of 13
ACCEPTED MANUSCRIPT 14
both compounds in a range of solvents. Unfortunately, the three recorded solubilities in water for acetylferrocene are all different, values of log Sw being -2.32 [52], -1.491 [53] and -1.41 [8]. We therefore used only the solubility values of log Ss in water-ethanol mixtures [53], obtain the corresponding values of log Ps, as shown in Table 6, and then used the log Ps values in the usual way to obtain descriptors for acetylferrocene. These yielded 26 equations, and we had another two equations from an experimental value of
T
2.1 for log Ps into wet octanol [50], making a total of 28 equations. We took E = 1.537
IP
by addition of fragments and V = 1.5018 calculated as for ferrocene. Then analysis of the
CR
28 equations yielded the descriptors shown in Table 4 with an SD of 0.082 log units between calculated and observed values. The twelve calculated and observed values of
US
log Ps obtained from solubilities are in Table 6 and yield AE = 0.002, AAE = 0.040, RMSE = 0.047 and SD = 0.051. Exactly the same statistics will be found for the
AN
corresponding values of log Ss using log Sw = -1.49 [53].
M
Table 6
Calculated and observed values of log Ps for acetylferrocene and diacetylferrocene
Acetylferrocene Calc Obs 2.139 2.213 2.141 2.165 2.139 2.159 2.134 2.132 2.040 2.031 1.841 1.837 1.652 1.597 1.394 1.323 1.111 1.039 0.774 0.759 0.443 0.494 0.163 0.240
Diacetylferrocene Calc
Obs
AC
CE
PT
Solvent Ethanol 96% vol Ethanol-water 95% vol Ethanol-water 90% vol Ethanol-water 80% vol Ethanol-water 70% vol Ethanol-water 60% vol Ethanol-water 50% vol Ethanol-water 40% vol Ethanol-water 30% vol Ethanol-water 20% vol Ethanol-water 10% vol Ethanol-water
ED
at 298 K
14
1.770 1.785 1.681 1.511 1.320 1.103 0.795 0.486 0.208
1.715 1.663 1.651 1.564 1.396 1.165 0.894 0.606 0.304
ACCEPTED MANUSCRIPT 15
The discrepancies in solubilities noted for acetylferrocene are apparent also for diacetylferrocene. We deduced E = 1.680 by addition of fragments, and calculated V = 1.7993. We took the solubilities in water-ethanol mixtures [53] and obtained values of log Ps from log Sw = - 1.725. There are fewer data points than for acetylferrocene, and the fit is not so good. For 20 equations we obtained SD = 0.099 log units. The observed and calculated values of log Ps are in Table 6 and can be converted into corresponding
T
log Ss values through log Sw = -1.725. For the observed and calculated values AE =
IP
0.033, AAE = 0.079, RMSE = 0.085 and SD = 0.090 log units for the nine sets of data.
determined
for
both
acetoacetylferrocene
CR
Solubilities in water-methanol [54] and water-ethanol [55] mixtures have been and
1,1-bis(acetoacetyl)ferrocene,
US
diacetoacetylferrocene. In both cases, the solubility in water-methanol mixtures, and hence log P for water-methanol mixtures, was far larger than the corresponding values in
AN
water-ethanol mixtures, and far larger than we calculated by any reasonable set of descriptors. This is illustrated by the plots of log P for diacetoacetylferrocene shown in
M
Figure 1. Since the same group of workers carried out the solubility measurements in both aqueous alcohols, we rule out any experimental error and suggest that methanol
ED
could form solvates with both of the substituted ferrocenes. Vasiliev et al. [56] have determined the X-ray structure and also the NMR spectrum in deuterochloroform of
PT
diacetoacetylferrocene but neither of these studies leads to any indication of why methanol, specifically, could form solvates.
Using just the solubility data in water-
CE
ethanol mixtures, we obtained the descriptors shown in Table 4 for acetoacetylferrocene with SD = 0.050 for 26 equations, and SD = 0.138 for diacetoacetylferrocene from 18
AC
equations. A plot of observed and calculated log P values for the latter is in Figure 1. The descriptors for acetoacetylferrocene and diacetoacetylferrocene are based only on a restricted type of solvent, and we suggest should be taken as provisional only.
15
ACCEPTED MANUSCRIPT 16
4
T
2
IP
Log P
3
CR
1
10
20
30
40 50 Vol% alcohol
60
70
80
90
AN
0
US
0
M
Figure 1. Values of log Ps for diacetoacetylferrocene in aqueous alcohols: ○ Observed values in water-methanol, □ calculated values in water – methanol, ● observed values in
PT
ED
water- ethanol, ■ calculated values in water-ethanol
Other substituted ferrocenes. A certain amount of data is available for
CE
ferrocenylcarbinol, Ferr-CH2OH, ferrocenylmethylcarbinol,
Ferr-CH(Me)OH, and
ferrocenyldimethylcarbinol, Ferr-C(Me)2OH. Water-octanol partition coefficients are
AC
known for ferrocenylcarbinol, log Ps = 2.0 [50], and for ferrocenylmethylcarbinol, log Ps = 2.3 [50], and there have been studies on the solubility of ferrocenyldimethylcarbinol in various organic solvents [8] and in some water-ethanol mixtures [9], For these carbinols, there is the additional A-descriptor to determine. Only for ferrocenyldimethylcarbinol is there enough data to obtain all the required descriptors, but we found that the two sets of data [8, 9] were not internally compatible and we were unable to deduce any reasonable set of descriptors. We have values of E (Table 3) for alkylferrocenes, we can calculate V and we know that A = 0. We know also that values of S, B and especially L vary regularly along 16
ACCEPTED MANUSCRIPT 17
any homologous series [57, 58] and so we can estimate descriptors for alkylferrocenes by comparison with ferrocene itself and homologous series. We particularly used descriptors for cyclohexane and alkylcyclohexanes so that, for example L(alkylferrocene) = L(ferrocene) + L(alkylcyclohexane – L(cyclohexane). We were able to obtain a set of descriptors for simple alkylferrocenes in this way, as given in Table 4. The descriptors
T
form a coherent series, as shown by the regular change in log Kw with the alkyl group.
IP
4. Conclusions
CR
We have shown that exactly the same methods that we have used to obtain Abraham (Absolv) descriptors for a variety of organic compounds can be applied to a series of
US
substituted ferrocenes. However, there were difficulties in the assignment of the E and V descriptors that had to be overcome when dealing with these compounds that contained
AN
an iron atom, and we envisage similar difficulties in the determination of descriptors for compounds such as inorganic complexes. Once the difficulties over E and V are
M
overcome, it is apparent that substituted ferrocenes can be dealt with in exactly the same way as typical organic compounds, with substituent effects falling into similar patterns.
ED
The descriptors for ferrocene and substituted ferrocenes can be used to estimate log Ps values for partition into a very large number of organic and aqueous organic phases,
PT
see Table 1. These estimated log Ps values can in turn be used to obtain the corresponding solubilities through Eq. 3 provided that the water solubility, as log Ss is
AC
Funding
CE
known.
This research received no grants from any funding agencies in the public, commercial, or not-for-profit sectors.
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T
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IP
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CR
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ED
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AC
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[13]
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physicochemical and biochemical processes, Chem. Soc. Revs. 22 (1993) 73-83. [14] M. H. Abraham, A. Ibrahim, A. M. Zissimos, The determination of sets of solute descriptors from chromatographic measurements, J. Chromatogr.A 1037 (2004) 29-47.
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T
[15] C. F. Poole, S. N. Atapattu, S. K. Poole and A. K. Bell, Determination of solute descriptors by chromatographic methods, Anal. Chim. Acta 652 (2009) 32-53.
CR
properties of compounds from chromatographic measurements and the solvation parameter model, J. Chromatogr. A 1317 (2013) 85-104.
US
[17] E. D. Clarke and L. Mallon, “The Determination of Abraham descriptors and their Application to Crop Protection Research”, in Modern Methods in Crop Protection
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ED
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PT
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CE
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AC
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[23] M. H. Abraham and W. E. Acree, Jr., Partition coefficients and solubilities of compounds in the water-ethanol solvent system, J. Soln. Chem. 40 (2011) 1279-1290. [24] T. W. Stephens, N. E. De La Rosa, M. Saifullah, S. Ye, V. Chou, A. N. Quay, W.E.Acree, Jr. and M. H. Abraham, Abraham model correlations for solute partitioning into o-xylene, m-xylene and p-xylene from both water and the gas phase, Fluid Phase Equilib. 308 (2011) 64-71.
T
[25] T. W. Stephens, N. E. De La Rosa, M. Saifullah, S. Ye, V. Chou, A. N. Quay, W. E.
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CR
molecules and ions to sulfolane, Fluid Phase Equilib. 309 (2011) 30-35. [26] T. W. Stephens, A. N. Quay, V. Chou, M. Loera, C. Shen, A. Wilson, W. E. Acree,
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ED
[28] M. Saifullah, S. Ye, L. M. Grubbs, N. E. De La Rosa, W. E. Acree, Jr. and M. H. Abraham, Abraham model correlations for the transfer of neutral molecules to
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tetrahydrofuran and to 1,4-dioxane and for transfer of ions to tetrahydrofuran, J. Soln. Chem. 40 (2011) 2082-2094.
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[29] T. W. Stephens, M. Loera, A. N. Quay, V. Chou, C. Shen, A. Wilson, W. E. Acree, Jr. and M. H. Abraham, Correlation of solute transfer into toluene and ethylbenzene from
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water and from the gas phase based on the Abraham model, Open Thermodyn. J. 5 (2011) 104-121.
[30] T. W. Stephens, A. Wilson, N. Dabadge, A. Tian, H. J. Hensley, M. Zimmerman, W. E. Acree, Jr. and M. H. Abraham, Correlation of solute partitioning into isooctane from water and from the gas phase based on updated Abraham equations, Global J. Phys. Chem. 3 (2012) 9 [31] M. H. Abraham and W. E. Acree, Jr., Equations for the partition of neutral molecules, ions and ionic species from water to water-ethanol mixtures, J. Soln. Chem. 41 (2012) 730-740. 20
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[32] M. Brumfield, W. E. Acree Jr. and M. H. Abraham, Abraham model correlations for describing solute transfer into diisopropyl ether, Phys. Chem. Liq. 53 (2015) 25-37. [33] M. Brumfield, A. Wadawadigi, N. Kuprasertkul, S. Mehta, W. E. Acree Jr. and M. H. Abraham, Abraham model correlations for solute transfer into tributyl phosphate from both water and the gas phase, Phys. Chem. Liq. 53 (2015) 10-24.
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[34] I. A. Sedov, M. A. Stolov, E. Hart, D. Grover, H. Zetti, V. Koshevarova, C. Dai, S.
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Zhang, W. E. Acree, Jr., and M. H. Abraham, Abraham model correlations for describing
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solute transfer into 2-butoxyethanol from both water and the gas phase at 298K, J. Mol. Liq. 209 (2015) 196-202.
[35] E. Hart, D. Grover, H. Zettl, V. Koshevarova, S. Zhang, C. Dai, W. E. Acree, Jr., I.
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A. Sedov, M. A. Stolov, and M. H. Abraham, Abraham model correlations for solute transfer into 2-methoxyethanol from water and from the gas phase, J. Mol. Liq. 209
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(2015) 738-744.
[36] M. H. Abraham, M. Zad and W. E. Acree, Jr., The transfer of neutral molecules
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from water and from the gas phase to solvents acetophenone and aniline, J. Mol. Liq. 212
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(2015) 301-306.
[37] D. M. Stovall, A. Schmidt, C. Dai, S. Zhang, W. E. Acree Jr. and M. H. Abraham, Abraham model correlations for estimating solute transfer of neutral compounds into
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anhydrous acetic acid from water and from the gas phase, J. Mol. Liq. 212 (2015) 16-22. [38] I. A. Sedov, D. Khaibrakhmanova, E. Hart, D. Grover, H. Zetti, V. Koshevarova, C.
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Dai, S. Zhang, A. Schmidt, W. E. Acree, Jr., and M. H. Abraham, Development of Abraham model correlations for solute transfer into both 2-propoxyethanol and 2-
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isopropoxyethanol at 298.15 K, J. Mol. Liq. 212 (2015) 833-840. [39] M. H. Abraham and W. E. Acree, Jr., Equations for the partition of neutral molecules, ions and ionic species from water to water-methanol mixtures. J. Soln. Chem. 45 (2016) 861-874 [40] W. E. Acree Jr., M. Y. Horton, E. Higgins and M. H. Abraham, Abraham model linear free energy relationships as a means of extending solubility studies to include the estimation of solute solubilities in additional organic solvents, J. Chem. Thermodynam. 102 (2016) 392-397.
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[41] I. A. Sedov, T. Salikov, E. Hart, E. Higgins, W. E. Acree Jr. and M. H. Abraham, Abraham model linear free energy relationships for describing the partitioning and solubility behaviour of nonelectrolyte organic solutes dissolved in pyridine at 298.15 K, Fluid Phase Eq. 431 (2017) 66-74. [42] M. H. Abraham and J. C. McGowan, The use of characteristic volumes to measure cavity terms in reversed-phase liquid chromatography. Chromatographia 23 (1987) 243-
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Electroanal. Chem. 599 (2007) 12-22. [51] ChemSketch. ACD Advanced Chemistry Development, 110 Yonge Street, 14th Floor, Toronto, Ontario, M5C 1T4, Canada. [52] F. A. Buryukin, V. P. Tverdokhlebov, V. A. Fedorov, E. V. Tetenkova, A. V. Fedorova and O. O. Azanova, The solubility of acetylferrocene and diacetylferrocene in dimethylsulfoxide and its mixtures with water, Russ. J. Phys. Chem. 82 (2008) 15451548.
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[53] A. V. Zakharenko, P. V. Fabinskii, O. M. Batalova, V. P. Tverdokhlebov and V. A. Fedorov, Solubility of acetyl- and diacetyl-ferrocene in mixed aqueous-alcoholic solvents. Russ. J. Gen. Chem. 73 (2003) 70-74. [54] E. E. Sergeev, P. V. Fabinskii and V. A. Fedorov, Temperature dependences of the solubility of acetoacetylferrocene and 1,1’-bis(acetoacetyl)ferrocene in water-methanol mixed solvents, Russ. J. Phys. Chem. 81 (2007) 1054-1058.
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[58] UFZ-LSER data base: S.Endo, T. N. Brown, N. Watanabe, N. Ulrich, G., Bronner,
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Bullet points
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w.ufz.de/lserd http://www.ufz.de/lserd.
Solubilities of ferrocene in 58 solvents examined Abraham descriptors for ferrocene and substituted ferrocenes determined Ferrocene is hydrophobic, with no acidity, little basicity but with moderate dipolarity Solubilities and partition properties of the ferrocenes can be estimated
Cover letter
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We have compiled a list of solubilities of ferrocene in 58 solvents, and used these to obtain the corresponding water-solvent partition coefficients. From the latter, we have obtained Abraham descriptors and can use these to estimate water-solvent partition coefficients and solubilities of ferrocene in a large number of other solvents. The descriptors show that ferrocene is hydrophobic, with no hydrogen bond acidity, little hydrogen bond basicity, but with a significant dipolarity. Descriptors for a number of
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substituted ferrocenes have also been obtained. It is thus shown that our general method
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for determination of descriptors for organic compounds is applicable to the set of
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ferrocenes, and that in principle descriptors can be obtained for any substituted ferrocene. Furthermore, the analysis we have made on ferrocene descriptors will enable descriptors
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to be obtained for cyclopentadiene derivatives of other transition metals. This greatly enlarges the scope of our descriptor method and should be of interest to all those
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interested in physicochemical properties of organic compounds and, now, organic
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compounds of transition elements.
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