Hydrolysis of .alpha.-methoxystyrenes. Molecular orbital-perturbation analysis of substituent effects and the relation between hydration and solvolysis reactions

1974 ◽  
Vol 96 (14) ◽  
pp. 4508-4517 ◽  
Author(s):  
Gordon M. Loudon ◽  
Carl Berke
Keyword(s):  
Molecular Orbital ◽  
Perturbation Analysis ◽  
Substituent Effects ◽  
Orbital Perturbation ◽  
Hydrolysis Of

Kinetic study of hydrolysis of benzoates. part xxvii. ortho substituent effect in alkaline hydrolysis of phenyl esters of substituted benzoic acids in aqueous Bu4NBr

2009 ◽  
Vol 74 (1) ◽  
pp. 29-42 ◽  
Author(s):  
Vilve Nummert ◽  
Mare Piirsalu ◽  
Signe Vahur ◽  
Oksana Travnikova ◽  
Ilmar A. Koppel
Keyword(s):  
Alkaline Hydrolysis ◽  
Rate Constants ◽  
Pure Water ◽  
Substituent Effects ◽  
Benzoic Acids ◽  
Resonance Effects ◽  
The Media ◽  
Substituted Benzoic Acids ◽  
Hydrolysis Of ◽  
Ortho Substituent

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.

Kinetic Study of Hydrolysis of Benzoates. Part XXVI. Variation of the Substituent Effect with Solvent in Alkaline Hydrolysis of Substituted Alkyl Benzoates

2006 ◽  
Vol 71 (11-12) ◽  
pp. 1557-1570 ◽  
Author(s):  
Vilve Nummert ◽  
Mare Piirsalu ◽  
Ilmar A. Koppel
Keyword(s):  
Kinetic Study ◽  
Alkaline Hydrolysis ◽  
Rate Constants ◽  
Substituent Effect ◽  
Substituent Effects ◽  
Alkyl Substituent ◽  
Solvent Parameters ◽  
Substituent Constants ◽  
Hydrolysis Of ◽  
Main Factor

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.

Substituent Effects in the Carboxypeptidase A Catalyzed Hydrolysis of Substituted L,.beta.-Phenyllactate Esters

Biochemistry ◽  
1994 ◽  
Vol 33 (49) ◽  
pp. 14750-14757 ◽  
Author(s):  
Alan Osumi ◽  
Abdulkader Rahmo ◽  
Stephen W. King ◽  
Theodore J. Przystas ◽  
Thomas H. Fife
Keyword(s):  
Substituent Effects ◽  
Carboxypeptidase A ◽  
Hydrolysis Of

Photoelectron (HeI) Spectra of Aromatic Thiocarbonyls and Corresponding S-Oxides

1978 ◽  
Vol 33 (4) ◽  
pp. 468-471
Author(s):  
Fernando Bernardi ◽  
Francesco Paolo Colonna ◽  
Giuseppe Distefano ◽  
Gaetano Maccagnani ◽  
Giuseppe Spunta
Keyword(s):  
Molecular Orbital ◽  
Ionization Energy ◽  
Substituent Effects ◽  
Molecular Orbital Theory ◽  
Orbital Theory

The low ionization energy regions of the photoelectron (He I) spectra of several p-p′-substituted thiobenzophenones (X-C6H4)2CS and of the corresponding S-oxides (sulphines) (XC6H4)2CSO (where X = H , OCH3, CH3, I, Br, Cl and NO2) have been assigned on the basis of perturbational molecular orbital theory arguments coupled with CNDO/2 computations and substituent effects. For the thioketones, the ordering of the outermost MO's results to be n(S), π7, π6, π5/π4, π3, n(S) being the HOMO; while for the sulphines the two outermost MO’s have π character and correspond to π7 and π6 in the thioketones.In the light of the above results the different behaviour toward oxidation of these two classes of compounds can be rationalized.

Molecular orbital calculations for sulphur-nitrogen heterocycles. I. The 3-hydroxyisothiazole system

1968 ◽  
Vol 21 (5) ◽  
pp. 1113 ◽  
Author(s):  
JR Christie ◽  
B Selinger
Keyword(s):  
Molecular Orbital ◽  
Perturbation Analysis ◽  
Related Species ◽  
Nitrogen Heterocycles ◽  
Chemical Properties ◽  
Molecular Orbital Calculations ◽  
Semi Empirical ◽  
Scf Calculations

LCAO-SCF calculations of various types have been performed for 3-hydroxy-isothiazole and related species. A perturbation analysis has shown that the values assigned to some of the semi-empirical parameters affect the results to a greater extent than has been supposed. Some of the chemical properties can be rationalized on the basis of these calculations.

Sign in / Sign up

Export Citation Format

Share Document