Consider the following compounds:

Arrange these compounds in the increasing order of rate of hydrolysis:

(B) < (D) < (A) < (C)

The correct answer is Option (2) → (B) < (D) < (A) < (C).

The names of the given compounds are:

To arrange the given compounds in increasing order of their rate of hydrolysis, we need to consider the electronic effects of the substituents on the benzoyl chloride group. Hydrolysis of benzoyl chlorides involves the attack of water on the carbonyl carbon, and the rate of this reaction depends on how electron-deficient the carbonyl carbon is. Electron-withdrawing groups (EWGs) increase the electron deficiency on the carbonyl carbon, making it more reactive towards nucleophilic attack (in this case, water), thereby increasing the rate of hydrolysis.

Analysis of Each Compound:

A. 4-Formylbenzoyl chloride:

The formyl group (-CHO) at the para position is an electron-withdrawing group (EWG) due to its ability to withdraw electron density via both the inductive and resonance effects.

This increases the electron deficiency on the carbonyl carbon, making it more susceptible to nucleophilic attack and increasing the rate of hydrolysis.

High rate of hydrolysis.

B. 4-Hydroxybenzoyl chloride:

The hydroxy group (-OH) at the para position is an electron-donating group (EDG) through resonance, which reduces the electron deficiency on the carbonyl carbon, making it less reactive towards nucleophiles like water.

Low rate of hydrolysis due to this electron-donating effect.

C. 4-Nitrobenzoyl chloride:

The nitro group (-NO₂) is a strong electron-withdrawing group (EWG) through both inductive and resonance effects. This group significantly increases the electron deficiency on the carbonyl carbon, making it highly reactive towards nucleophiles like water.

Very high rate of hydrolysis due to the strong electron-withdrawing effect.

D. Benzoyl chloride:

Benzoyl chloride has no substituent, so the reactivity depends only on the carbonyl group itself.

Moderate rate of hydrolysis.

Increasing Order of Rate of Hydrolysis:

The rate of hydrolysis will increase with the increasing electron-withdrawing nature of the substituents. Electron-donating groups will decrease the rate of hydrolysis, while electron-withdrawing groups will increase it.

Based on the analysis:

4-Hydroxybenzoyl chloride (B) has the lowest rate of hydrolysis due to the electron-donating hydroxy group.

Benzoyl chloride (D) is more reactive than (B) due to the lack of any strong electron-donating or withdrawing groups.

4-Formylbenzoyl chloride (A) has a higher rate of hydrolysis than (D) because the formyl group is electron-withdrawing.

4-Nitrobenzoyl chloride (C) has the highest rate of hydrolysis due to the strong electron-withdrawing nitro group.

Correct Order of Increasing Rate of Hydrolysis: \((B) < (D) < (A) < (C)\)