In the following reaction, the absolute configurations of the chiral centres in X and Y are A. 2S, 3R and 2R, 3R B. 2R, 3R and 2R, 3S C. 2S, 3S and 2R, 3R D. 2S, 3R and 2S, 3R

[amp_mcq option1=”2S, 3R and 2R, 3R” option2=”2R, 3R and 2R, 3S” option3=”2S, 3S and 2R, 3R” option4=”2S, 3R and 2S, 3R” correct=”option1″]

The correct answer is A. 2S, 3R and 2R, 3R.

The absolute configuration of a chiral center is the spatial arrangement of the four groups attached to the chiral center. The absolute configuration is designated by the R or S system, which is based on the Cahn-Ingold-Prelog priority rules.

In the reaction shown, the chiral center in X is the carbon atom with the hydroxyl group attached. The priority of the groups attached to this carbon atom is as follows:

1. Hydroxyl group (-OH)
2. Methyl group (-CH3)
3. Ethyl group (-CH2CH3)
4. Hydrogen atom (-H)

The absolute configuration of the chiral center in X is R, because the hydroxyl group is in the R configuration.

The chiral center in Y is the carbon atom with the bromide group attached. The priority of the groups attached to this carbon atom is as follows:

1. Bromide group (-Br)
2. Methyl group (-CH3)
3. Ethyl group (-CH2CH3)
4. Hydrogen atom (-H)

The absolute configuration of the chiral center in Y is R, because the bromide group is in the R configuration.

Therefore, the absolute configurations of the chiral centers in X and Y are 2S, 3R and 2R, 3R, respectively.