Electrostatic effects on ionization equilibria. Carboxylic acids and amines derived from 1-indanone

1978 ◽  
Vol 43 (12) ◽  
pp. 3227-3240 ◽  
Author(s):  
Otto Exner ◽  
Zdeněk Friedl
Keyword(s):  
Carboxylic Acids ◽  
Electrostatic Effects ◽  
Ionization Equilibria

Electrostatic effects on ionization equilibria: Solvent dependence

1984 ◽  
Vol 49 (1) ◽  
pp. 179-189 ◽  
Author(s):  
Karel Kalfus ◽  
Zdeněk Friedl ◽  
Otto Exner
Keyword(s):  
Gas Phase ◽  
Carboxylic Acids ◽  
Dissociation Constants ◽  
Aprotic Solvents ◽  
Benzoic Acids ◽  
Cavity Model ◽  
Electrostatic Effects ◽  
Solvent Dependence ◽  
Ionization Equilibria ◽  
Substituted Benzoic Acids

Apparent dissociation constants of 3-substituted bicyclo[2,2,2]-octane-1-carboxylic acids I-III and of several substituted benzoic acids were measured in four pure solvents. The results - together with numerous literature data concerning dissociation in other solvents and in the gas phase - were compared with the prediction of the electrostatic theory. The theory fails to reproduce the essential features of the solvent dependence as it predicts generally too small effects and does not differentiate between protic and aprotic solvents. The mentioned goal cannot be achieved by any more sophisticated cavity model or by any other theory as far as it characterizes the solvent only through its bulk permittivity.

Electrostatic effects on ionization equilibria. 3-Substituted bicyclo[2,2,2]octane-1-carboxylic acids

1979 ◽  
Vol 44 (10) ◽  
pp. 2928-2945 ◽  
Author(s):  
Zdeněk Friedl ◽  
Jaroslav Hapala ◽  
Otto Exner
Keyword(s):  
Carboxylic Acids ◽  
Substituent Effects ◽  
Molecular Size ◽  
Geometrical Parameters ◽  
Electrostatic Effects ◽  
Ellipsoidal Cavity ◽  
Theoretical Predictions ◽  
Ionization Equilibria ◽  
The One

Nine 3-substituted (I-IX) and one 2-substituted (XI) bicyclo[2,2,2]octane-1-carboxylic acids were prepared as model compounds for verification of the electrostatic theory of substituent effects. On the one hand they are regular-shaped and suitable for calculations, on the other hand they allow to evaluate the role of the angle θ of the substituent dipole. The apparent pK values in 50% ethanol and 80% methyl cellosolve were correlated with σI constants (ρI 1.18 and 1.42, respectively) and compared with theoretical predictions based on the spherical and ellipsoidal cavity models. The agreement is very good with the new Ehrenson model but still satisfactory with some others not matching exactly the actual molecule shape. The substituent effects are resonably correlated with the substituent dipoles and with the geometrical parameters but exceptions are notable. Comparison with the previous results implies that the theory reproduces fairly the substituent effects in carboxylic acids of a given molecular size and not too unsymmetrical shape; the cavity model is, however, sufficiently flexible to compensate partly even for some non-electrostatic effects neglected by the basic theory.

CORRELATION OF O–H STRETCHING FREQUENCIES WITH pK VALUES FOR SOME PHENOLS

1957 ◽  
Vol 35 (12) ◽  
pp. 1555-1560 ◽  
Author(s):  
P. M. G. Bavin ◽  
William J. Canady
Keyword(s):  
Carbon Tetrachloride ◽  
Carboxylic Acids ◽  
Carbon Disulphide ◽  
Substituted Phenols ◽  
Electrostatic Effects ◽  
Single Straight Line ◽  
Linear Relationships ◽  
Straight Line ◽  
Alcohol Water

The O–H stretching frequencies, in carbon disulphide, of a number of phenols have been determined. Linear relationships were observed on plotting the stretching frequency against pKA in water. Polar substituted phenols were found to fall along one line, while phenols substituted with aliphatic groups were found to fall along another line of different slope. A change of slope is observed when the stretching frequencies of phenols are plotted against pKA measured in alcohol–water mixtures.Using Goulden's O–H stretching frequencies of carboxylic acids measured in carbon tetrachloride, an attempt has been made to explain the observed deviations from a single straight line in terms of electrostatic effects in the ionizing solvent. The results indicate that for the substances examined, such effects are not responsible for the observed deviations.

Electrostatic Effects in Ionization Equilibria: An AM1 Study of Reversed Substituent Effect in 5-Fluorobicyclo[3.3.3]undecane-1-carboxylic Acid

1994 ◽  
Vol 59 (7) ◽  
pp. 1467-1471
Author(s):  
Zdeněk Friedl ◽  
Stanislav Böhm
Keyword(s):  
Carboxylic Acid ◽  
Proton Transfer ◽  
Substituent Effect ◽  
Am1 Method ◽  
Electrostatic Effects ◽  
Ionization Equilibria ◽  
Electrostatic Theory

Relative proton transfer enthalpies δ ∆H0 of sp and ap conformers of 5-fluorobicyclo[3.3.3]undecane-1-carboxylic acid have been calculated by the AM1 method and the results were compared with the prediction of the electrostatic theory. It is shown that the great reversed substituent effect in the sp conformer (δ ∆H0 = 32.1 kJ mol-1) is substantially overestimated largely due to sterical Baeyer strain and non-bonded interactions.

Electrostatic effects on ionization equilibria: MNDO study of proton and hydrogen transfer reactions of 5-fluoropentanoic acid

1985 ◽  
Vol 63 (5) ◽  
pp. 1068-1072 ◽  
Author(s):  
Zdenek Friedl
Keyword(s):  
Proton Transfer ◽  
Gas Phase ◽  
Carboxylic Acids ◽  
Hydrogen Transfer ◽  
Opposite Sign ◽  
Substituent Effects ◽  
Transfer Reactions ◽  
Small Contribution ◽  
Bond Strengths ◽  
Ionization Equilibria

Relative proton transfer enthalpies δΔH0 and homolytic bond strengths δΔH0 (A—H) of sp and ap conformers of 5-fluoropentanoic acid, as well as some related aliphatic and 4-X-bicyclo[2.2.2]octane-1-carboxylic halogenoacids, have been calculated by the MNDO method. The results, together with literature data concerning the gas phase acidities, were compared with the prediction of the electrostatic theory. It is shown that the substituent effects on acidities of carboxylic acids are largely due to substituent interactions in the anions and only to a smaller extent to interactions in the neutral acids. A small contribution (about one-eighth to one-fourth as large in magnitude but of opposite sign) is possibly also made by substituent effects on homolytic bond strengths DH0 (A—H).

Long-range electrostatic effects in biomolecular simulations

1997 ◽  
Vol 94 ◽  
pp. 1346-1364 ◽  
Author(s):  
TA Darden ◽  
A Toukmaji ◽  
LG Pedersen
Keyword(s):  
Long Range ◽  
Electrostatic Effects ◽  
Biomolecular Simulations

A convenient preparative method for 1,4-diketones from carboxylic acids

1977 ◽  
Vol 27 (1) ◽  
pp. 117-120
Author(s):  
Shoji Watanabe ◽  
Tsutomu Fujita ◽  
Kyoichi Suga ◽  
Haruhiko Abe
Keyword(s):  
Carboxylic Acids ◽  
Preparative Method
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