Question

The major obtained in the photo catalyzed bromination of 2-methyl butane is:
(A) 1-Bromo-2-methyl butane
(B) 1-Bromo-3-methyl butane
(C) 2-Bromo-3-methyl butane
(D) 2-Bromo-2-methyl butane

Answer 1

Hint: Photo - catalyzed bromination reaction involves a radical mechanism. Thus reaction proceeds via the formation of the most stable tertiary radical at the second carbon atom. So, from this, we can find the major obtained in this reaction.

Complete Solution :
We have been provided with the photo catalyzed bromination of 2-methyl butane,
We need to find the major that would be obtained.
So, for that:
- Catalysis of photochemical reaction which occurs at the solid surface is known as the photo catalysis reaction. This reaction usually takes place at the semiconductor surface.
Also, photo catalyzed bromination involves radical mechanism,
- A free-radical reaction is a chemical reaction involving free radicals. This reaction type is abundant in organic reactions,
- So, in the given reaction, the radical is formed at the second carbon due to the formation of the stable tertiary radical.
- A radical in which the unpaired electron is bonded to three carbon atoms is termed as the tertiary alkyl radical.
So, as a result, the Bromo radical attacks at this position and forms 2-Bromo-2-methyl butane as the major product.
So, we can say that the major obtained in the photo catalyzed bromination of 2-methyl butane is 2-Bromo-2-methyl butane. The reaction is as shown below:

The major product i.e. 2-bromo-2-methylbutane is obtained by replacing the tertiary hydrogen by the Bromo group. So, the correct answer is “Option D”.

Note: Radical would be formed at the less stable carbon as more stable carbon won’t allow the formation of the bond over it. So, that’s the reason that radical is formed at second carbon due to the stable tertiary carbon. Along with the major product we can obtain the minor product as the 2-bromo-3-methylbutane.But it is less stable and minor.