Steric substituent effect on the resin catalyzed hydrolysis of alkyl acetate esters

The second-order rate constants k2 (dm3 mol-1 s-1) for the alkaline hydrolysis of substituted alkyl benzoates C6H5CO2R have been measured spectrophotometrically in aqueous 0.5 M Bu4NBr at 50 and 25 °C (R = CH3, CH2Cl, CH2CN, CH2C≡CH, CH2C6H5, CH2CH2Cl, CH2CH2OCH3, CH2CH3) and in aqueous 5.3 M NaClO4 at 25 °C (R = CH3, CH2Cl, CH2CN, CH2C≡CH). The dependence of the alkyl substituent effects on different solvent parameters was studied using the following equations: ∆ log k = c0 + c1σI + c2EsB + c3∆E + c4∆Y + c5∆P + c6∆EσI + c7∆YσI + c8∆PσI ∆ log k = c0 + c1σ* + c2EsB + c3∆E + c4∆Y + c5∆P + c6∆Eσ* + c7∆Yσ* + c8∆Pσ* . ∆ log k = log kR - log kCH3. σI and σ* are the Taft inductive and polar substituent constants. E, Y and P are the solvent electrophilicity, polarity and polarizability parameters, respectively. In the data treatment ∆E = ES - EH2O , ∆Y = YS - YH2O , ∆P = PS - PH2O were used. The solvent electrophilicity, E, was found to be the main factor responsible for changes in alkyl substituent effects with medium. When σI constants were used, variation of the polar term of alkyl substituents with the solvent electrophilicity E was found to be similar to that observed earlier for meta and para substituents, but twice less when σ* constants were used. The steric term for alkyl substituents was approximately independent of the solvent parameters.

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Kinetic Study of Hydrolysis of Benzoates. Part XXV. Ortho Substituent Effect in Alkaline Hydrolysis of Phenyl Esters of Substituted Benzoic Acids in Water

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc20060107 ◽

2006 ◽

Vol 71 (1) ◽

pp. 107-128 ◽

Cited By ~ 16

Author(s):

Vilve Nummert ◽

Mare Piirsalu ◽

Vahur Mäemets ◽

Ilmar Koppel

Keyword(s):

Acid Hydrolysis ◽

Alkaline Hydrolysis ◽

Substituent Effect ◽

Ethyl Esters ◽

Benzoic Acids ◽

Neat Water ◽

Substituted Benzoic Acids ◽

Hydrolysis Of Esters ◽

Hydrolysis Of

The second-order rate constants k2 for alkaline hydrolysis of phenyl esters of meta-, para- and ortho-substituted benzoic acids, X-C6H4CO2C6H5 (X = H, 3-Cl, 3-NO2, 3-CH3, 4-NO2, 4-Cl, 4-F, 4-CH3, 4-OCH3, 4-NH2, 2-NO2, 2-CN, 2-F, 2-Cl, 2-Br, 2-I, 2-CH3, 2-OCH3, 2-CF3, 2-NH2), and of substituted phenyl esters of benzoic acid, C6H5CO2C6H4-X (X = 2-I, 2-CF3, 2-C(CH3)3, 4-Cl, 4-CH3, 4-OCH3, 4-NH2), have been measured spectrophotometrically in water at 25 °C. The substituent effect in alkaline hydrolysis of phenyl esters of para-substituted benzoic acids, similar to that for ethyl esters of para-substituted benzoic acids, was found to be precisely described by the Hammett relationship (ρ = 1.7 in water). The log k value for alkaline hydrolysis of phenyl and ethyl esters of meta-, para- and ortho-substituted benzoic acids, X-C6H4CO2R, was nicely correlated with log km,p,ortho = log ko + (ρ)m,pσ + (ρI)orthoσI + (ρ°R)orthoσ°R + δorthoEsB where σ, σI, σ°R are the Hammett polar, Taft inductive and Taft resonance (σ°R = σ° - σI) substituent constants, respectively. EsB is the steric scale for ortho substituents calculated on the basis of the log k values for the acid hydrolysis of ortho- substituted phenyl benzoates in water owing to the ortho substituent in the phenyl of phenyl benzoates. In water, the main factors responsible for changes in the ortho substituent effect in alkaline hydrolysis of phenyl and ethyl esters of ortho-substituted benzoic acids, X-C6H4CO2R, were found to be the inductive and steric factors while the role of the resonance term was negligible ((ρ°R)ortho ca. 0.3). In alkaline hydrolysis of substituted benzoates in neat water, the ortho inductive effect appeared to be 1.5 times and steric influence 2.7 times higher than the corresponding influences from the ortho position in the phenyl of phenyl benzoates. The contributions of the steric effects in alkaline hydrolysis of esters of ortho-substituted benzoic acids was found to be approximately the same as in acid hydrolysis of esters of ortho-substituted benzoic and acid esterification of ortho-substituted benzoic acids.

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Study of the substituent effect on α-chymotrypsin-catalyzed hydrolysis of phenyl acetates by using a stopped-flow titration method

Archives of Biochemistry and Biophysics ◽

10.1016/0003-9861(82)90476-3 ◽

1982 ◽

Vol 217 (1) ◽

pp. 37-46 ◽

Cited By ~ 9

Author(s):

Kazuhiko Ikeda ◽

Shigeru Kunugi ◽

Norio Ise

Keyword(s):

Substituent Effect ◽

Stopped Flow ◽

Titration Method ◽

Flow Titration ◽

Hydrolysis Of

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Substituent effect on the hydrolysis of chlorosilanes: quantum chemical and QSPR study

Structural Chemistry ◽

10.1007/s11224-016-0881-z ◽

2016 ◽

Vol 28 (2) ◽

pp. 333-343 ◽

Cited By ~ 3

Author(s):

Gergő Szabó ◽

László Nyulászi

Keyword(s):

Quantum Chemical ◽

Substituent Effect ◽

Qspr Study ◽

Hydrolysis Of

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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.

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