Cooperativity and anticooperativity in solvation by water: imidazoles, quinones, nitrophenols, nitrophenolate, and nitrothiophenolate ions
Equilibrium constants for transfer from water to vapor, determined by dynamic vapor pressure measurements, show that the hydrophilic character of imidazole (log K(v/w) = -7.2) is no greater than might be expected on the basis of its constituent groups, whereas p-nitrophenol (log K(v/w) = -8.6) is about 30-fold more hydrophilic than would be the case if the effects of its constituent groups were additive. In contrast, the p-nitrophenolate ion (estimated log K(v/w) = -46) is less hydrophilic, by approximately 15 orders of magnitude, than might be expected if there were no interactions between its substituent groups. Thiopicric acid yields the most hydrophobic benzenoid anion that appears to have been reported thus far, its dissociated tetraethylammonium salt entering methylene chloride from water with an equilibrium constant approaching unity. The hydrophilic character of p-benzoquinone (log K(v/w) = -4.3) is much exceeded by that of p-hydroquinone (log K(v/w) = -7.5), so that solvent water exerts a major effect on the redox potential of this system. Comparison with model compounds indicates that in both p-benzoquinone and p-hydroquinone, solvation requirements of the symmetrical polar substituents are in conflict.
- Research Organization:
- Univ. of North Carolina, Chapel Hill
- OSTI ID:
- 6970303
- Journal Information:
- J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 109:2; ISSN JACSA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400201* -- Chemical & Physicochemical Properties
AQUEOUS SOLUTIONS
AROMATICS
AZOLES
DATA
DISPERSIONS
EXPERIMENTAL DATA
FLUIDS
GASES
HETEROCYCLIC COMPOUNDS
HYDROGEN COMPOUNDS
HYDROXY COMPOUNDS
IMIDAZOLES
INFORMATION
MIXTURES
NITRO COMPOUNDS
NITROPHENOL
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
ORGANIC SULFUR COMPOUNDS
OXYGEN COMPOUNDS
PHENOLS
PHYSICAL PROPERTIES
QUINONES
REDOX POTENTIAL
SOLUTIONS
SOLVATION
SOLVENT PROPERTIES
THERMODYNAMIC PROPERTIES
THIOPHENOLS
VAPOR PRESSURE
VAPORS
WATER