Handbook of Solvents - George Wypych - ChemTech - Ventech!

5.5 The phenomenological theory of solvent effects 287
molecule. An experiment whose results are summarized in Table 5.5.1 was designed to examine
this possibility. 10
Table 5.5.1. Surface area estimates of biphenyls 10
Compound Atotal Anonpolar gA
Biphenyl 179 (3) 179 (3) 74 (0.6)
4-Hydroxybiphenyl 185 (4) 155 (7) 69 (0.3)
4,4’-Dihydroxybiphenyl 203 (5) 126 (7) 53 (0.5)
4-Bromobiphenyl 217 (7) 217 (7) 87 (1.4)
Areas in � 2 molecule; standard deviations in parentheses. The cosolvent was methanol.
Evidently the experimental gA estimate is correlated with A nonpolar rather than with
A total, and the linear relationship yields the estimate g = 0.37. On the other hand, there was
evidence 1 that g depends upon cosolvent identity (for a given solute), and LePree and
Mulski 8,11 examined this possibility. Their findings led to an empirical but quite general correlation
between gA and properties of the cosolvent and solute:
gA =− 42logP + 11log
P
[5.5.25]
M R
In eq. [5.5.25] P M is the 1-octanol/water partition coefficient of the pure organic
cosolvent and P R is the partition coefficient of the solute. Table 5.5.2 gives examples of the
application of eq. [5.5.25].
Table 5.5.2 Experimental and calculated gA values 8,11
Solute Solvent
gA, � 2 molecule -1
Calculated Observed
Naphthalene Methanol 66 63
Naphthalene Ethanol 48 54
Naphthalene 2-Propanol 35 43
Naphthalene 1,2-Propanediol 92 71
Naphthalene 1,2-Ethanediol 116 102
Naphthalene Acetone 45 69
Naphthalene DMSO 120 127
4-Nitroaniline Methanol 46 35
4-Nitroaniline Ethanol 29 21
4-Nitroaniline 2-Propanol 15 11
4-Nitroaniline 1,2-Ethanediol 96 84
4-Nitroaniline Acetone 25 37