Substituent Effects on the Acidity of Weak Acids. 2. Calculated Gas-Phase Acidities of Substituted Benzoic Acids

The second-order rate constants k (in dm3 mol–1 s–1) for alkaline hydrolysis of phenyl esters of meta-, para- and ortho-substituted benzoic acids, X-C6H4CO2C6H5, have been measured spectrophotometrically in aqueous 0.5 and 2.25 M Bu4NBr at 25 °C. The substituent effects for para and meta derivatives were described using the Hammett relationship. For the ortho derivatives the Charton equation was used. For ortho-substituted esters two steric scales were involved: the EsB and the Charton steric (υ) constants. When going from pure water to aqueous 0.5 and 2.25 M Bu4NBr, the meta and para polar effects, the ortho inductive and resonance effects in alkaline hydrolysis of phenyl esters of substituted benzoic acids, became stronger nearly to the same extent as found for alkaline hydrolysis of C6H5CO2C6H4-X. The steric term of ortho-substituted esters was almost independent of the media considered. The rate constants of alkaline hydrolysis of ortho-, meta- and para-substituted phenyl benzoates (X-C6H4CO2C6H5, C6H5CO2C6H4-X) and alkyl benzoates, C6H5CO2R, in water, 0.5 and 2.25 M Bu4NBr were correlated with the corresponding IR stretching frequencies of carbonyl group, (ΔνCO)X.

Download Full-text

Influence of Aprotic Solvents on the Transmission of Anomalous Substituent Effects on 13C NMR Chemical Shifts at the Carboxyl Carbon (δco) in Meta-Substituted Benzoic Acids: A Strong Evidence for π-Polarization Mechanism

Applied Magnetic Resonance ◽

10.1007/s00723-011-0276-7 ◽

2011 ◽

Vol 42 (3) ◽

pp. 321-332 ◽

Cited By ~ 1

Author(s):

Susanta K. Sen Gupta ◽

Ruchi Shrivastava

Keyword(s):

13C Nmr ◽

Strong Evidence ◽

Chemical Shifts ◽

Substituent Effects ◽

Aprotic Solvents ◽

Benzoic Acids ◽

13C Nmr Chemical Shifts ◽

Polarization Mechanism ◽

Substituted Benzoic Acids ◽

Carboxyl Carbon

Download Full-text

Analysis of the Gas Phase Acidity of Substituted Benzoic Acids Using Density Functional Concepts

Molecules ◽

10.3390/molecules25071631 ◽

2020 ◽

Vol 25 (7) ◽

pp. 1631

Author(s):

Jorge A. Amador-Balderas ◽

Michael-Adán Martínez-Sánchez ◽

Ramsés E. Ramírez ◽

Francisco Méndez ◽

Francisco J. Meléndez

Keyword(s):

Gas Phase ◽

Density Functional ◽

Chemical Potential ◽

Fukui Function ◽

Ortho Position ◽

Benzoic Acids ◽

Functional Theory ◽

Resonance Effects ◽

Gas Phase Acidity ◽

Substituted Benzoic Acids

A theoretical study of the effect of the substituent Z on the gas phase acidity of substituted benzoic acids ZC6H4COOH in terms of density functional theory descriptors (chemical potential, softness and Fukui function) is presented. The calculated gas phase ΔacidG° values obtained were close to the experimental ones reported in the literature. The good relationship between the ΔacidG° values and the electronegativity of ZC6H4COOH and its fragments, suggested a better importance of the inductive than polarizability contributions. The balance of inductive and resonance contributions of the substituent in the acidity of substituted benzoic acids showed that the highest inductive and resonance effects were for the -SO2CF3 and -NH2 substituents in the para- and ortho-position, respectively. The Fukui function confirmed that the electron-releasing substituent attached to the phenyl ring of benzoic acid decreased the acidity in the trend ortho > meta > para, and the electron-withdrawing substituent increased the acidity in the trend ortho < meta < para.

Download Full-text

Contribution to the study of the esterification mechanism in the gas phase of substituted benzoic acids on AlPO4

Reaction Kinetics and Catalysis Letters ◽

10.1007/bf02064397 ◽

1984 ◽

Vol 25 (3-4) ◽

pp. 181-186

Author(s):

A. Llobera ◽

J. V. Sinisterra

Keyword(s):

Gas Phase ◽

Benzoic Acids ◽

Substituted Benzoic Acids

Download Full-text

ChemInform Abstract: SUBSTITUENT EFFECTS ON THE INTRINSIC ACIDITIES OF BENZOIC ACIDS DETERMINED BY GAS PHASE PROTON TRANSFER EQUILIBRIA MEASUREMENTS

Chemischer Informationsdienst ◽

10.1002/chin.197434111 ◽

1974 ◽

Vol 5 (34) ◽

Author(s):

R. YAMDAGNI ◽

T. B. MCMAHON ◽

P. KEBARLE

Keyword(s):

Proton Transfer ◽

Gas Phase ◽

Substituent Effects ◽

Benzoic Acids

Download Full-text

Prediction of ortho substituent effect in alkaline hydrolysis of phenyl esters of substituted benzoic acids in aqueous acetonitrile

Open Chemistry ◽

10.2478/s11532-013-0321-5 ◽

2013 ◽

Vol 11 (12) ◽

pp. 1964-1975 ◽

Cited By ~ 1

Author(s):

Vilve Nummert ◽

Mare Piirsalu ◽

Ilmar Koppel

Keyword(s):

Alkaline Hydrolysis ◽

Rate Constants ◽

Substituent Effect ◽

Substituent Effects ◽

Benzoic Acids ◽

Aqueous Acetonitrile ◽

Substituent Constants ◽

Substituted Benzoic Acids ◽

Hydrolysis Of ◽

Ortho Substituent

AbstractThe second-order rate constants k for the alkaline hydrolysis of phenyl esters of meta-, para- and ortho-substituted benzoic acids, X-C6H4CO2C6H5, in aqueous 50.9% acetonitrile have been measured spectrophotometrically at 25°C. The log k values for meta and para derivatives correlated well with the Hammett σm,p substituent constants. The log k values for ortho-substituted phenyl benzoates showed good correlations with the Charton equation, containing the inductive, σI, resonance, σ○ R, and steric, E s B, and Charton υ substituent constants. For ortho derivatives the predicted (log k X)calc values were calculated with equation (log k ortho)calc = (log k H AN)exp + 0.059 + 2.19σI + 0.304σ○ R + 2.79E s B − 0.0164ΔEσI — 0.0854ΔEσ○ R, where DE is the solvent electrophilicity, ΔE = E AN — E H20 = −5.84 for aqueous 50.9% acetonitrile. The predicted (log k X)calc values for phenyl ortho-, meta- and para-substituted benzoates in aqueous 50.9% acetonitrile at 25°C precisely coincided with the experimental log k values determined in the present work.The substituent effects from the benzoyl moiety and aryl moiety were compared by correlating the log k values for the alkaline hydrolysis of phenyl esters of substituted benzoic acids, X-C6H4CO2C6H5, in various media with the corresponding log k values for substituted phenyl benzoates, C6H5CO2C6H4-X.

Download Full-text