Predict the productsand propose mechanisms for the following reactions.

The organic ester that forms when there is condensation reaction occurs between ethanol and benzoic acid is ethyl benzoate. This compound bears one ethyl group and one benzene ring.

The ethyl benzoate is subjected to acid treatment with an excess of water. The final product of this reaction will be benzoic acid. The reaction is given below.

There are several steps that take place in the mechanism. The steps are listed below.

A. Proton on leading to resonance stabilization.

B. Attack of the nucleophile.

C. Proton off.

D. Proton on.

E. Leaving group exit leading to resonance stabilization.

F. Proton off.

The sketch of the mechanism is given below

(b) The ethyl benzoate is subjected to base treatment with an excess of water. The final product of this reaction will be benzoate ions and ethanol. The reaction is given below.

The hydroxide ion attacks the carbonyl carbon of ethyl benzoate leading to the formation of an ion in which the carbonyl oxygen bears a negative charge and carbonyl carbon gets attached to the OH group.

By resonance stabilization, there is the formation of alcohol. Ethoxide ion attacks the alcoholic group which leads to the formation of ethanol and benzoate ion. The mechanism is shown below.

(c) The 4-hydroxybutanoic acid is subjected to acid treatment. Then, the water is removed. This will result in the formation of a lactone whose name is dihydrofuran-2(3H)-one. The chemical reaction is shown below.

The hydrogen ion of the acid attacks the carbonyl carbon of 4-hydroxybutanoic acid leading to the formation of an ion in which the carbonyl oxygen bears a positive charge. By resonance stabilization, there is the formation of alcohol.

The removal of water leads to some resonance structure and by some rearrangements, there is a formation of a cyclic structure called lactone. The cyclic structure is a five-membered ring. The mechanism is shown below.

(d) The 4-hydroxybutanoic acid is subjected to base treatment. Then, water is removed. This will result in the formation of an ion whose name is 4-hydroxybutanoate along with water. The chemical reaction is shown below.

The lone pairs of the hydroxide ion attack the hydrogen of the COOH group. The oxygen atom gets a negative charge that is an ion called 4-hydroxybutanoate. The by-product formed is water. The mechanism is shown below.