Thermodynamics of ionization processes in aqueous solution. Part 1.—General theory of substituent effects

Equilibrium constants for hydrate–hemiacetal interconversion in aqueous solution at 25° have been measured for four fluorinated carbonyl compounds: compound, alcohol, K4 (M−1): CF3CHO, C2H5OH, 2.3; CF3COCH3, CH3OH, 1.0; CF3COPh, CH3OH, 3.5; CF3COCF3, CH3OH, 0.14. These values, combined with values from the literature, permit an examination of substituent effects upon the equilibrium constant for[Formula: see text]The free energy change for this process, corrected for symmetry and steric effects, follows the equation[Formula: see text]Thus electronic effects upon this equilibrium are generally small and in fact are often smaller than steric effects.This analysis permits and justifies the calculation of free energies of formation of [Formula: see text] compounds from the (more generally measurable) free energies of formation of the analogous [Formula: see text] compounds.

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ChemInform Abstract: THERMODYNAMICS OF IONIZATION PROCESSES FOR NITRO-SUBSTITUTED BENZOIC ACIDS IN WATER-DIMETHYLSULFOXIDE MIXTURES AT 25°C

Chemischer Informationsdienst ◽

10.1002/chin.197952060 ◽

1979 ◽

Vol 10 (52) ◽

Author(s):

F. RODANTE

Keyword(s):

Benzoic Acids ◽

Ionization Processes ◽

Substituted Benzoic Acids ◽

Thermodynamics Of Ionization

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A Comparison of Substituent Effects on the Stability of .alpha.,.alpha.-Dimethylbenzyl Carbocations in Aqueous Solution and in the Gas Phase: How Significant is Nucleophilic Solvation?

Journal of the American Chemical Society ◽

10.1021/ja00094a028 ◽

1994 ◽

Vol 116 (15) ◽

pp. 6706-6712 ◽

Cited By ~ 20

Author(s):

John P. Richard ◽

Vandannapu Jagannadham ◽

Tina L. Amyes ◽

Masaaki Mishima ◽

Yuho Tsuno

Keyword(s):

Aqueous Solution ◽

Gas Phase ◽

Substituent Effects ◽

The Stability ◽

Nucleophilic Solvation

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Thermodynamic functions of ionization of t-butyl-substituted and methoxysubstituted phenols

Australian Journal of Chemistry ◽

10.1071/ch9720075 ◽

1972 ◽

Vol 25 (1) ◽

pp. 75 ◽

Cited By ~ 5

Author(s):

PD Bolton ◽

FM Hall ◽

J Kudrynski

Keyword(s):

Aqueous Solution ◽

Thermodynamic Functions ◽

Spectrophotometric Method ◽

Substituent Effects ◽

Steric Effects ◽

Ionization Process ◽

Ionization Constants ◽

Temperature Range

Thermodynamic ionization constants of 2-t-butylphenol, 3-t-butylphenol, 4-t-butylphenol, 3,5-di-t-butylphenol, and 3,5-dimethoxyphenol have been measured in aqueous solution by an e.m.f./spectrophotometric method within the temperature range 5-60�C and the thermodynamic functions of ionization ΔG25, ΔH25, ΔS25, and ΔCp25 calculated. These results confirm the additivity of substituent effects noted previously for the ionization of 3,5-disubstituted phenols and indicate that this ionization process is relatively insensitive to steric effects.

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