The Hydrolysis of Cyclic Orthoesters. Stereoelectronic Control in the Cleavage of Hemiorthoester Tetrahedral Intermediates

1975 ◽  
Vol 53 (11) ◽  
pp. 1601-1615 ◽  
Author(s):  
Pierre Deslongchamps ◽  
Robert Chênevert ◽  
Roland J. Taillefer ◽  
Claude Moreau ◽  
John K. Saunders
Keyword(s):  
Experimental Evidence ◽  
Acid Hydrolysis ◽  
Alkoxy Group ◽  
Gauche Conformer ◽  
Group A ◽  
Stereoelectronic Control ◽  
Hydroxy Esters ◽  
Hydrolysis Of Esters ◽  
Hydrolysis Of ◽  
Tetrahedral Intermediates

The synthesis of several cyclic dialkoxy orthoesters is reported. Acid hydrolysis of these orthoesters under kinetically controlled conditions gives the corresponding hydroxy esters only. Conformationally rigid cyclic mixed orthoesters give a hydroxy ester by exclusive loss of the axial alkoxy group. A cyclic orthoester can have nine different gauche conformations. It is shown that they are hydrolyzed through only one gauche conformer. These results bring further experimental evidence that there is a stereoelectronic control in the cleavage of tetrahedral intermediates in the hydrolysis of esters.

The products of hydrolysis of cyclic orthoesters as a function of pH and the theory of stereoelectronic control

1985 ◽  
Vol 63 (9) ◽  
pp. 2485-2492 ◽  
Author(s):  
Pierre Deslongchamps ◽  
Jean Lessard ◽  
Yves Nadeau
Keyword(s):  
Acid Hydrolysis ◽  
Hydroxy Ester ◽  
The Other ◽  
Relative Percentage ◽  
Stereoelectronic Control ◽  
Hydrolysis Of ◽  
Tetrahedral Intermediates

The acid hydrolysis of cyclic orthoesters 1, 3–6 (R = Me), and 2 (R = Me and Et) as a function of pH was studied. The bicyclic orthoester 5 yields mainly the hydroxy-ester (less than 5% lactone), and this result is essentially independent of pH. For the other orthoesters, the relative percentage of products differs for each case and varies with pH. At pH ≤ 3, the percentage of lactone is always larger than at pH > 3. These results are explained on the basis of the stereoelectronic theory for the cleavage of tetrahedral intermediates.

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

2006 ◽  
Vol 71 (1) ◽  
pp. 107-128 ◽  
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.

Sign in / Sign up

Export Citation Format

Share Document