Substituent effects. III. Dissociation constants of .beta.-arylpropionic acids, .beta.-arylisovaleric acids, N-arylglycines, aryloxyacetic acids, N-aryl-.beta.-alanines, and some related systems

1973 ◽  
Vol 95 (16) ◽  
pp. 5350-5356 ◽  
Author(s):  
A. J. Hoefnagel ◽  
J. C. Monshouwer ◽  
E. C. G. Snorn ◽  
B. M. Wepster
Keyword(s):  
Dissociation Constants ◽  
Substituent Effects

Effects of Medium and Substituents on Dissociationof 4,4'-Disubstituted Bis(benzenesulfon)imides

1996 ◽  
Vol 61 (8) ◽  
pp. 1205-1214 ◽  
Author(s):  
Miroslav Ludwig ◽  
Pavel Štverka
Keyword(s):  
Latent Variables ◽  
Dissociation Constants ◽  
Substituent Effects ◽  
Principal Component ◽  
H Nmr ◽  
Base Process ◽  
Elemental Analyses ◽  
Substituent Constants ◽  
Model Substances ◽  
Strong Acids

Ten 4,4'-disubstituted bis(arenesulfon)imides of the general formula XC6H4SO2NHSO2C6H4X have been synthesized and their structures confirmed by their 1H NMR spectra. Elemental analyses are presented for the compounds not yet described. The dissociation constants of these model substances have been measured potentiometrically in pyridine, dimethylformamide, methanol, ethanol, propylene carbonate, acetone, acetonitrile, 1,2-dichloroethane and tetramethylene sulfone. The pKHA values obtained have been correlated with three sets of the Hammett substituent constants and the results have been used to discuss the solvent and substituent effects on the dissociation of the compounds studied. Sulfonimides with electron-acceptor substituents behave as rather strong acids in some solvents (pyridine, dimethylformamide, methanol and ethanol), whereas normal substituent dependences are found in other solvents. The experimental data have also been interpreted with the help of the statistical methods based on latent variables. From the calculations it follows that only the first principal component, which correlates well with the substituent constant sets adopted, is statistically significant in describing the substituent effect on the acid-base process studied.

scholarly journals Substituent Effects on the Dissociation Constants of 1-Aryl-5-hydroxy-2-hydroxymethyl-4-pyridones

1983 ◽  
Vol 56 (6) ◽  
pp. 1879-1880
Author(s):  
Kimiaki Imafuku ◽  
Kumio Takahashi ◽  
Hisashi Matsumura
Keyword(s):  
Dissociation Constants ◽  
Substituent Effects

Substituent effects on polarographic reduction of some photographic color intermediates

1976 ◽  
Vol 54 (8) ◽  
pp. 1205-1210 ◽  
Author(s):  
Ahmad S. Shawali ◽  
Bahgat E. El-Anadouli
Keyword(s):  
Dissociation Constants ◽  
Substituent Effects ◽  
Protonated Form ◽  
Acid Dissociation ◽  
Polarographic Reduction ◽  
Substituent Constant ◽  
Acid Dissociation Constants ◽  
Controlled Potential Electrolysis ◽  
Half Wave ◽  
Controlled Potential

Polarographic reduction of two series of benzoylacetanilides has been investigated in 40% (by volume) ethanolic Britton–Robinson buffers. One series (A) contains substituents on the anilide moiety, and the second (B) has substituents on both the anilide and benzoyl moieties. Polarographic controlled-potential electrolysis data indicate that the electroactive species in both series is the protonated form (ArCOCH2CONHAr′)H+. The reduction half-wave potentials of anilides of series A were found to be independent of the nature of the substituent, whereas those of series B show a good linear relationship when plotted vs. the σ substituent constant of the substituent on the benzoyl moiety (ρ = 0.284, r = 0.995). Values of the acid dissociation constants of the keto (K1) and enol (K2) tautomers of the anilides of series A were calculated; unlike their E1/2 values, the pK1 data show a linear correlation with the Hammett substituent constant, σ. The pK2 values show, however, little variation with σ.

A Study of Transmission Effects of Sulfonyl and Carbonyl Groups

1995 ◽  
Vol 60 (5) ◽  
pp. 841-850 ◽  
Author(s):  
Miroslav Ludwig ◽  
Patrik Pařík ◽  
Jiří Kulhánek
Keyword(s):  
Latent Variables ◽  
Dissociation Constants ◽  
Substituent Effects ◽  
Principal Component ◽  
Carbonyl Groups ◽  
H Nmr ◽  
Deviation Analysis ◽  
Substituent Constants ◽  
The Difference ◽  
Latent Structures

Seventeen p-substituted N-phenylsulfonylbenzamides of general formulas XC6H4SO2NHCOC6H5 and C6H5SO2NHCOC6H4X have been synthesized and their structure has been confirmed by elemental analysis and 1H NMR spectra. The dissociation constants of all the compounds have been measured by potentiometric titration in methanol, acetonitrile, dimethylformamide, dimethyl sulfoxide, and pyridine. The obtained pKHA values have been correlated with three sets of Hammett substituent constants using simple or double linear regression. The solvent and substituent effects are discussed on the basis of experimental results, and the difference between the substituent effects from sulfonamide and benzamide sections is evaluated. It has been found that due to the extensive delocalization of negative charge in the conjugated base the transmission effects of carbonyl and sulfonyl groups on the transmission of substituent effect are roughly the same. The experimental data have been interpreted by the methods with latent variables: the principal component analysis (PCA), the conjugated deviation analysis (CDA), and the method of projection to latent structures (PLS). The results obtained by these procedures were similar.

Ortho Effect in Dissociation of Substituted N-Phenylbenzenesulfonamides

2001 ◽  
Vol 66 (9) ◽  
pp. 1380-1392 ◽  
Author(s):  
Jiří Nádvorník ◽  
Miroslav Ludwig
Keyword(s):  
Experimental Data ◽  
Latent Variables ◽  
Dissociation Constants ◽  
Substituent Effects ◽  
Principal Component ◽  
Steric Effects ◽  
Deviation Analysis ◽  
Acid Base Equilibrium ◽  
The Difference ◽  
Electronic And Steric Effects

Twenty-five 2,2'-disubstituted N-phenylbenzenesulfonamides (2-X-C6H4SO2NHC6H4-Y-2') were synthesised and their purity checked by elemental analysis. This set of model substrates involved all possible combinations of methoxy, methyl, hydrogen, chloro, and nitro substituents. The dissociation constants of the sulfonamides were determined by potentiometric titration in methanol, pyridine, dimethyl sulfoxide, N,N-dimethylformamide, acetone, and acetonitrile. The dissociation constants pKHA obtained were correlated with various sets of substituent constants describing electronic and steric effects of the substituents, and the statistically treated data were used to discuss the contribution of the substituent effects in the dissociation and the difference between the effects transmitted from the two rings. A linear regression model explaining 99% of the variability of experimental data in all the solvents has been found and discussed. Moreover, the experimental data were also interpreted by the methods using latent variables, the principal component analysis (PCA) and conjugated deviation analysis (CDA), and two latent variables were shown to be statistically significant in the description of dissociation. The first obviously describes common action of electronic and steric effects of substituents; the other probably concerns a combined effect of substituent and solvent on the position of acid-base equilibrium.

Acid-Base Properties of Substituted Naphthoic Acids in Nonaqueous Media

1997 ◽  
Vol 62 (11) ◽  
pp. 1737-1746 ◽  
Author(s):  
Patrik Pařík ◽  
Miroslav Ludwig
Keyword(s):  
Experimental Data ◽  
Linear Regression ◽  
Latent Variables ◽  
Latent Variable ◽  
Dissociation Constants ◽  
Substituent Effects ◽  
Acid Base ◽  
Nonaqueous Media ◽  
Substituent Constants ◽  
Substituted 1

Thirteen substituted 1-naphthoic acids have been prepared and their dissociation constants, along with those of twenty-five substituted 2-naphthoic acids, have been measured potentiometrically in methanol, N,N-dimethylformamide, pyridine, and acetonitrile. The pKHA values obtained have been treated by linear regression using four sets of substituent constants. The experimental data have also been interpreted by statistical methods using latent variables. The first latent variable calculated by these methods can be used as a new set of substituent constants for describing substituent effects in naphthalene skeleton.

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.

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