Question

The isomeric deuterated bromide with molecular formula $C _4 H _8 DBr$ having two chiral carbon atoms is

• A. 2 - Bromo - 1 - deuterobutane
• B. 2 - Bromo - 2 - deuterobutane
• C. 2 - Bromo - 3 - deuterobutane
• D. 2 - Bromo-1 - deutero - 2 - methylpropane

Answer 1

The Correct Option is C

To determine the correct isomeric deuterated bromide with molecular formula C _4 H _8 DBr that has two chiral carbon atoms, we need to analyze each option given:

1. 2 - Bromo - 1 - deuterobutane: This compound corresponds to C_4H_8DBr with a structure where the bromine is at the second carbon, and deuterium (D) is at the first carbon. However, this configuration results in only one chiral center at the second carbon, not two.
2. 2 - Bromo - 2 - deuterobutane: Here, both bromine and deuterium are attached to the second carbon. This makes the second carbon chiral; however, the presence of a symmetrical configuration with identical groups (bromine and deuterium on the same carbon) prevents the existence of a second chiral center.
3. 2 - Bromo - 3 - deuterobutane: The compound is structured with bromine on the second carbon and deuterium on the third carbon. This configuration results in each of the second and third carbons being bonded to four different groups, making both chiral. This fulfills the requirement of having two chiral centers.
4. 2 - Bromo-1 - deutero - 2 - methylpropane: In this structure, the bromine is at the second carbon, the deuterium is at the first carbon, and it's a branch with a methyl group. Only the second carbon would be chiral due to unique substituents, not both the first and second carbons.

By process of elimination and analysis of the structure, 2 - Bromo - 3 - deuterobutane is the correct answer as it is the only one with two chiral centers:

• The bond arrangement in 2 - Bromo - 3 - deuterobutane is as follows, ensuring chirality at both the second and third carbon positions due to different substituents around these carbons.

Thus, the correct option with two chiral carbons is indeed 2 - Bromo - 3 - deuterobutane.