Which of the following is true for the given reaction?

Tertiary amines do not contain any replaceable 'H' on amino group

The correct answer is option 1. Tertiary amines do not contain any replaceable 'H' on amino group.

Let us delve into why tertiary amines do not react with benzene sulphonyl chloride and why the other options are not correct:

Reaction with Benzene Sulphonyl Chloride

Benzene sulphonyl chloride (\( \text{C}_6\text{H}_5\text{SO}_2\text{Cl} \)) is a reagent that reacts with amines to form sulphonamides. This reaction generally proceeds via the following mechanism:

Nucleophilic Attack: The amine (which has a lone pair of electrons on nitrogen) attacks the electrophilic sulfur in benzene sulphonyl chloride.

Formation of Sulphonamide: The result is the formation of a sulphonamide and the release of hydrochloric acid (HCl).

Why Tertiary Amines Do Not React

Tertiary Amines Lack Replaceable Hydrogen Atoms:

Primary and Secondary Amines: In primary amines (\( \text{RNH}_2 \)) and secondary amines (\( \text{R}_2\text{NH} \)), the nitrogen atom has one or two hydrogen atoms that can be replaced. These hydrogen atoms are involved in the reaction with benzene sulphonyl chloride, where the amino group of the amine reacts with the sulphonyl chloride to form a sulphonamide.

Tertiary Amines: In tertiary amines (\( \text{R}_3\text{N} \)), the nitrogen is bonded to three alkyl or aryl groups and has no hydrogen atoms. Since the reaction mechanism requires the replacement of a hydrogen atom, tertiary amines are incapable of undergoing this reaction because there are no hydrogen atoms to be replaced.

Analysis of the Given Options

1. Tertiary Amines Do Not Contain Any Replaceable 'H' on Amino Group:

The statement is true. Tertiary amines lack hydrogen atoms on the nitrogen, so they cannot react with benzene sulphonyl chloride. This is the main reason why the reaction does not occur.

2. It Is Very Bulky Due to Many \(-CH_3\) Groups:
The statement is not entirely true. While tertiary amines are indeed bulky due to the presence of multiple alkyl groups, steric hindrance is not the main reason why the reaction does not occur. The primary reason is the lack of replaceable hydrogen atoms.

3. Lone Pair of Electrons on Nitrogen Does Not Allow This Reaction:

The statement is false. The lone pair of electrons on the nitrogen in tertiary amines is available for potential reactions, but it does not participate in this particular reaction with sulphonyl chloride because the reaction mechanism requires a replaceable hydrogen atom.

4. \(SO_2\) Is Eliminated and Stops the Reaction:

The statement is false. In the reaction mechanism with benzene sulphonyl chloride, sulfur dioxide (\(SO_2\)) is not a product that is released. Instead, the reaction typically produces a sulphonamide and hydrochloric acid. The lack of a replaceable hydrogen atom is why tertiary amines do not react, not because of the elimination of \(SO_2\).

Tertiary amines do not react with benzene sulphonyl chloride because they lack the replaceable hydrogen atoms that are necessary for the formation of sulphonamides. This makes option 1 the correct explanation.