Further studies an the extended Hammett equation comprising the hydrophobic constant: Reactivity data for benzoic acids, arylacetic acids, β-arylpropionic acids, trans- and cis-cinnamic acids, methyl benzoates; dissociation constants, DDM reaction and alkaline hydrolysis in various water-organic solvent mixtures

1990 ◽  
Vol 55 (1) ◽  
pp. 119-135 ◽  
Author(s):  
Anthonius J. Hoefnagel ◽  
Bartholomeus M. Wepster
Keyword(s):  
Organic Solvent ◽  
Alkaline Hydrolysis ◽  
Dissociation Constants ◽  
Solvent Mixtures ◽  
Benzoic Acids ◽  
Hammett Equation ◽  
Cinnamic Acids ◽  
Tert Butanol ◽  
Arylacetic Acids

The extended Hammett eguaition Δ = ρs + hπ comprising the hydrophobic constant π is found to be effective in the title compounds and reactivities in various solvent mixtures. In 32 vol.% tert-butanol-water hmdecreases in the order ArCOOMe (-0.25), cis-ArCH=CHCOOH (-0.18), ArCOOH and ArCH2COOH (-0.16), ArCH2CH2COOH and trans-ArCH=CHCOOH (-0.07). For ArCOOH, mixtures like 40-60% methanol, 50% ethanol, 50% acetone and 50% dioxane give similar hm values of circa -0.05. For ArCH2COOH the effects of 3-iodo and 4-iodo substituents are acid-weakening in 32% tert-butanol. The consequences of the hπ term for ρ, σ, and the averaging of σ values, are discussed.

Mathematical representation of apparent dissociation constants in aqueous–organic solvent mixtures

2002 ◽  
Vol 246 (1-2) ◽  
pp. 135-142 ◽  
Author(s):  
Abolghasem Jouyban ◽  
Hak-Kim Chan ◽  
Brian J. Clark ◽  
William E. Acree
Keyword(s):  
Organic Solvent ◽  
Dissociation Constants ◽  
Mathematical Representation ◽  
Solvent Mixtures

Solvent effects on dissociation of substituted benzenesulphonamides in acetone, 1,2-dichloroethane, tetramethylene sulphone, pyridine and some aqueous organic solvent mixtures

1986 ◽  
Vol 51 (9) ◽  
pp. 1948-1957 ◽  
Author(s):  
Miroslav Ludwig ◽  
Oldřich Pytela ◽  
Miroslav Večeřa
Keyword(s):  
Organic Solvent ◽  
General Formula ◽  
Potentiometric Titration ◽  
Solvent Effects ◽  
Dissociation Constants ◽  
Dimethyl Sulphoxide ◽  
Organic Component ◽  
Solvent Mixtures

The potentiometric titration has been used to measure dissociation constants of fifteen substituted arenesulphonamides of general formula XC6H4SO2NH2 (or X2C6H3SO2NH2) in acetone, 1,2-dichloroethane, tetramethylene sulphone, pyridine, and mixtures water-ethanol (25, 50, 75, 90% by vol. of the organic component), water-dimethylformamide (25, 50, 75% by vol.), water-acetone (25% by vol.), and water-2-methoxyethanol (80% by wt.). The results are compared with those published earlier for water, methanol, ethanol, dimethylformamide, dimethyl sulphoxide, and acetonitrile.

Chemometrical Analysis of Substituent Effects. IV. Additivity of Substituent Effects in Dissociation of 3,5-Disubstituted Benzoic Acids in Organic Solvents

1994 ◽  
Vol 59 (7) ◽  
pp. 1637-1644 ◽  
Author(s):  
Oldřich Pytela ◽  
Jiří Kulhánek ◽  
Miroslav Ludwig
Keyword(s):  
Organic Solvents ◽  
Dissociation Constants ◽  
Quantitative Description ◽  
Substituent Effects ◽  
Benzoic Acids ◽  
Hammett Equation ◽  
Specific Solvation ◽  
Reaction Constant ◽  
Substituent Constants ◽  
The Individual

Ten 3,5-disubstituted benzoic acids have been synthesized containing all possible combinations of the following substituents: CH3O, CH3, Cl/Br, NO2. The dissociation constants of these acids have been measured in seven organic solvents (methanol, acetone, dimethyl sulfoxide, dimethylformamide, acetonitrile, pyridine, 1,2-dichloroethane). It has been found that the effect of disubstitution is smaller than that due to interaction of substituents or their solvation and represents only about 0.2% of the effect caused by the individual substituents. The additivity in 3,5-disubstitution is about 2 - 3 times as good as that in 3,4-disubstitution. The quantitative description of substituent effects at the 3 and 5 positions is additive within the range of validity of the Hammett equation irrespective of the type of the substituent constants adopted, the addition of the multiplicative term being statistically insignificant. The solvent effect on 3,4- and 3,5-disubstituted derivatives is somewhat different at the same value of the reaction constant, due predominantly to the specific solvation of the 4-CH3O and 4-NO2 groups.

Dissociation constants of substituted benzoic acids in water and in organic solvents

1986 ◽  
Vol 51 (10) ◽  
pp. 2135-2142 ◽  
Author(s):  
Miroslav Ludwig ◽  
Václav Baron ◽  
Karel Kalfus ◽  
Oldřich Pytela ◽  
Miroslav Večeřa
Keyword(s):  
Potentiometric Titration ◽  
Organic Solvents ◽  
Solvent Effects ◽  
Dissociation Constants ◽  
Point Of View ◽  
Benzoic Acids ◽  
Hammett Equation ◽  
Substituent Constant ◽  
Reaction Constant ◽  
Substituted Benzoic Acids

Potentiometric titration has been used to measure dissociation constants of 38 monosubstituted benzoic acids in water and in 6 organic solvents (methanol, ethanol, dimethylformamide, acetonitrile, sulfolane, acetone). The results have been analyzed and interpreted from the point of view of substituent and solvent effects on the dissociation of the title substrates. It has been proved that solvents affect not only the reaction constant but also the substituent constant of the Hammett equation.

Solvent Effect on the Hammett Reaction Constant of Substituted Benzoic Acids

1993 ◽  
Vol 46 (1) ◽  
pp. 31 ◽  
Author(s):  
H Bartnicka ◽  
I Bojanowska ◽  
MK Kalinowski
Keyword(s):  
Solvent Effect ◽  
Dimethyl Sulfoxide ◽  
Dissociation Constants ◽  
Benzoic Acids ◽  
Hammett Equation ◽  
P Values ◽  
Reaction Constant ◽  
Substituted Benzoic Acids ◽  
Reaction Constants ◽  
Solvent Acidity

Potentiometric titration has been used to measure dissociation constants of 13 monosubstituted benzoic acids in nitromethane, benzonitrile , acetonitrile , propylene carbonate, acetone, N,N-dimethylformamide, dimethyl sulfoxide, methanol and formamide. The reaction constants of the Hammett equation were found to depend on the solvent acidity and basicity expressed by the α and β parameters of Kamlet and Taft. The p values determined earlier in water and ethanol also obey this rule.

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