A. List the following esters in order of decreasing...

a. List the following esters in order of decreasing reactivity toward hydrolysis:
b. How would the rate of hydrolysis of the para-methylphenyl ester compare with the rate
of hydrolysis of these three esters?

Key Concepts

Ester Hydrolysis Mechanism

This concept involves understanding how esters react with water (often under acidic or basic conditions) to generate a carboxylic acid (or its salt) and an alcohol. The mechanism generally follows an addition–elimination pathway where the carbonyl carbon is attacked by a nucleophile, leading to a tetrahedral intermediate that then collapses, expelling a leaving group. Studying this mechanism helps in predicting the relative rates of hydrolysis based on structural features that affect nucleophilic attack and intermediate stability.

Leaving Group Ability

Leaving group ability is a major factor influencing the rate of ester hydrolysis. Better leaving groups stabilize the negative charge more effectively after departure, thereby lowering the activation energy for the reaction. In comparing different esters, those with a leaving group that is more stable once it has departed will generally hydrolyze more rapidly.

Electronic Effects on Reactivity

Electronic effects, such as inductive withdrawal and resonance donation, play a key role in determining the reactivity of esters toward hydrolysis. Electron-withdrawing groups increase the electrophilicity of the carbonyl carbon, making it more susceptible to nucleophilic attack, whereas electron-donating groups decrease electrophilicity. Additionally, resonance stabilization in aromatic esters (such as para-methylphenyl esters) can delocalize charge and affect the overall reactivity, altering the rate of hydrolysis relative to aliphatic counterparts.

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