Edited by JohnABarry at 2024-4-24 22:31
S.L. Johnson,
General Base and Nucleophilic Catalysis of Ester Hydrolysis and Related Reactions,
Editor(s): V. Gold,
Advances in Physical Organic Chemistry,
Academic Press,
Volume 5,
1967,
Pages 237-330,
ISSN 0065-3160,
ISBN 9780120335053,
https://doi.org/10.1016/S0065-3160(08)60312-3.
Abstract: Publisher Summary
This chapter illustrates the general base and nucleophilic catalysis of ester hydrolysis and related reactions. Displacement reactions at the carbonyl carbon are more facile than at saturated carbon because: (1) the carbonyl carbon has a sizeable, partial positive charge due to the polarization of the electrons in the carbonyl group towards the oxygen, making nucleophilic attack at this center easier, (2) in carboxylic acid derivatives containing leaving groups of low basicity, the main energy barrier in a displacement reaction is the addition of the nudeophile to the carbonyl bond, which involves the breaking of the relatively weak carbonyl ¦Ð-bond. In contrast, displacement reactions at saturated carbon involve the more highly energetic process of making and breaking of carbon ¦Ò-bonds, (3) the reaction center at the trigonal carbonyl carbon is less sterically hindered than at the sp3 hybridized saturated carbon. The entering group attacks the carbonyl carbon in the direction perpendicular to the trigonal plane that is at the carbon p-orbital, such that maximal overlap of the bonding orbital of the nucleophile with the carbon p orbital is possible.
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