Solvent dependence of pyridine aza sigma values determined from alkaline ester hydrolysis

1972 ◽  
Vol 25 (11) ◽  
pp. 2363 ◽  
Author(s):  
LW Deady ◽  
RA Shanks
Keyword(s):  
Alkaline Hydrolysis ◽  
Ester Hydrolysis ◽  
Aqueous Methanol ◽  
Solvent Dependence ◽  
Hydrolysis Of

The alkaline hydrolysis of a series of substituted alkyl benzoates and pyridine-carboxylates in aqueous methanol, dioxan, acetone, and DMSO solvents has been studied. Hammett correlations in all solvents are excellent and sigma values for the 2-, 3-, and 4-aza groups have been derived. These are effectively solvent independent except for a significant decrease in the σ2N value in DMSO-containing solvents.

Studies on the BAL2 mechanism for ester hydrolysis

1993 ◽  
Vol 71 (11) ◽  
pp. 1841-1844 ◽  
Author(s):  
Judy E. Douglas ◽  
Grant Campbell ◽  
Donald C. Wigfield
Keyword(s):  
Spectral Analysis ◽  
Carboxylic Acid ◽  
Alkaline Hydrolysis ◽  
Ester Hydrolysis ◽  
Mass Spectral Analysis ◽  
Mass Spectral ◽  
Hydrolysis Of

The preparation and alkaline hydrolysis of 18O-methyl 2,2-dimethylpropanoate and 18O-methyl triphenylacetate are reported. From mass spectral analysis of the carboxylic acid products, it is concluded that the former substrate is hydrolyzed exclusively by the BAC2 mechanism, whereas the latter substrate proceeds 95% by the BAC2 mechanism and 5% by the BAL2 mechanism. The balance between these two mechanisms is discussed.

Substitutent Effects in Non-Aromatic Nitrogen Heterocycles: Alkaline Hydrolysis of Methyl N-Methyl (oxo)dihydropyridinecarboxylates and Diaza Analogues

1985 ◽  
Vol 38 (4) ◽  
pp. 637 ◽  
Author(s):  
LW Deady
Keyword(s):  
Alkaline Hydrolysis ◽  
Nitrogen Heterocycles ◽  
Reaction Rates ◽  
Ester Hydrolysis ◽  
Pyrimidine Derivatives ◽  
Polyfunctional Compounds ◽  
Hydrolysis Of ◽  
Derivatives Of

Ester hydrolysis studies on some isomeric methoxycarbonyl derivatives of N-methylpyridin-2- and 4-ones show that reaction rates are affected by the relative positions of CO2Me, =O and NMe functions in ways which could not be predicted. However, from limited result for analogous pyrimidine derivatives, it seems that reactivity in these polyfunctional compounds can be predicted from the pyridine data by assuming additivity of effects.

scholarly journals Modeling the Alkaline Hydrolysis of Diaryl Sulfate Diesters: A Mechanistic Study

2020 ◽  
Author(s):  
Klaudia Szeler ◽  
Nicholas Williams ◽  
Alvan C. Hengge ◽  
Shina Caroline Lynn Kamerlin
Keyword(s):  
Alkaline Hydrolysis ◽  
Computational Study ◽  
Transition States ◽  
Building Blocks ◽  
Ester Hydrolysis ◽  
Mechanistic Study ◽  
Phosphate Ester ◽  
Sulfate Ester ◽  
The Impact ◽  
Hydrolysis Of

<div> <div> <div> <p>Phosphate and sulfate esters have important roles as biological building blocks and in regulating cellular processes. However, while there has been substantial experimental and computational investigation of the mechanisms and the transition states involved in phosphate ester hydrolysis, there is far less (in particular computational) work on sulfate ester hydrolysis. Here, we report a detailed computational study of the alkaline hydrolysis of diaryl sulfate diesters, using different DFT functionals and both pure implicit solvation as well as mixed implicit/explicit solvation with varying numbers of explicit water molecules. We consider both the impact of how the system is modeled on computed linear free energy relationships (LFER) and the nature of the transition states. Although our calculations consistently underestimate the absolute activation free energies, we obtain good agreement with experimental LFER data when using pure implicit solvent, and excellent agreement with experimental kinetic isotope effects for all models used. Our calculations suggest that the hydrolysis of sulfate diesters proceeds through loose transition states, with minimal bond formation to the nucleophile and with bond cleavage to the leaving group already initiated. Comparison to prior work indicates that these transition states are similar in nature to those of analogous reactions such as the alkaline hydrolysis of neutral arylsulfonate monoesters or charged phosphate diesters and fluorophosphates. Obtaining more detailed insight into the transition states involved assists in understanding the selectivity of enzymes that hydrolyze these reactions; however, this work also highlights the methodological challenges involved in reliably modeling sulfate ester hydrolysis. </p> </div> </div> </div>

scholarly journals Modeling the Alkaline Hydrolysis of Diaryl Sulfate Diesters: A Mechanistic Study

2020 ◽  
Author(s):  
Klaudia Szeler ◽  
Nicholas Williams ◽  
Alvan C. Hengge ◽  
Shina Caroline Lynn Kamerlin
Keyword(s):  
Alkaline Hydrolysis ◽  
Computational Study ◽  
Transition States ◽  
Building Blocks ◽  
Ester Hydrolysis ◽  
Mechanistic Study ◽  
Phosphate Ester ◽  
Sulfate Ester ◽  
The Impact ◽  
Hydrolysis Of

<div> <div> <div> <p>Phosphate and sulfate esters have important roles as biological building blocks and in regulating cellular processes. However, while there has been substantial experimental and computational investigation of the mechanisms and the transition states involved in phosphate ester hydrolysis, there is far less (in particular computational) work on sulfate ester hydrolysis. Here, we report a detailed computational study of the alkaline hydrolysis of diaryl sulfate diesters, using different DFT functionals and both pure implicit solvation as well as mixed implicit/explicit solvation with varying numbers of explicit water molecules. We consider both the impact of how the system is modeled on computed linear free energy relationships (LFER) and the nature of the transition states. Although our calculations consistently underestimate the absolute activation free energies, we obtain good agreement with experimental LFER data when using pure implicit solvent, and excellent agreement with experimental kinetic isotope effects for all models used. Our calculations suggest that the hydrolysis of sulfate diesters proceeds through loose transition states, with minimal bond formation to the nucleophile and with bond cleavage to the leaving group already initiated. Comparison to prior work indicates that these transition states are similar in nature to those of analogous reactions such as the alkaline hydrolysis of neutral arylsulfonate monoesters or charged phosphate diesters and fluorophosphates. Obtaining more detailed insight into the transition states involved assists in understanding the selectivity of enzymes that hydrolyze these reactions; however, this work also highlights the methodological challenges involved in reliably modeling sulfate ester hydrolysis. </p> </div> </div> </div>

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