Q.Phenyl benzoate, C6H5-O-CO-C6H5 (the benzoate ester of phenol), is treated with NaOH solution. Identify the product(s). (Two or more options may be correct.)

Ester Hydrolysis – From Intuition to Precision

Think of an ester as a molecule that was built by stitching together a carboxylic acid and an alcohol, with a water molecule squeezed out as a byproduct. That stitching is called esterification. Hydrolysis is simply the reverse: you bring water back in to break the ester apart, reclaiming the original acid and alcohol.

The name itself tells you the story: hydro (water) + lysis (to break). Water does the breaking.

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The Core Reaction

An ester has the general structure R–COO–R' , where the two R groups are carbon chains. When water attacks, the bond between the carbonyl carbon and the –OR' group snaps. One fragment gets an –OH (becoming the carboxylic acid), and the other gets an –H (becoming the alcohol).

In plain chemical terms:

Ester + Water → Carboxylic Acid + Alcohol

But here's the catch: water alone is a very slow, lazy attacker. You need a catalyst to speed things up. The catalyst can be either an acid or a base — and the choice changes what you actually get.

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Acid-Catalysed Hydrolysis

Under acidic conditions, the reaction is exactly the balanced reverse of esterification. You add dilute acid (like $\ce{H2SO4}$ or $\ce{HCl}$) and heat the mixture.

The acid protonates the carbonyl oxygen, making the carbon more electrophilic and vulnerable to water's attack. The reaction is reversible — you never get 100% conversion unless you drive it by using excess water or removing one product.

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Base-Catalysed Hydrolysis (Saponification)

Under basic conditions, something different happens. The base (typically $\ce{NaOH}$ or $\ce{KOH}$) doesn't just catalyse — it consumes the carboxylic acid as soon as it forms, turning it into a carboxylate salt.

Because the acid is removed from the equilibrium, the reaction goes to completion. This is irreversible. The products are a carboxylate salt (not the free acid) and an alcohol.

This is exactly the chemistry behind soap-making — hence the name saponification (from Latin sapo, soap). Animal fats (which are esters called triglycerides) are boiled with lye ($\ce{NaOH}$) to produce soap (the salt of a long-chain fatty acid) and glycerol.

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The Key Difference at a Glance