Question

The correct statement(s) for the following addition reactions is/are:

• A. O and P are identical molecules
• B. (M & O) and (N & P) are two pairs of diastereomers
• C. (M & O) and (N & P) are two pairs of enantiomers
• D. Bromination proceeds through trans-addition in both given reactions.

Answer 1

Answer: (B), (D)

The correct options are
B (M & O) and (N & P) are two pairs of diastereomers
D Bromination proceeds through trans-addition in both given reactions.

Let us start with trans-but-2-ene and subject it to bromine addition across the double bond:

There is just the one product - the optically inactive meso-2,3-dribromobutane.
Both M and N are identical (they are both the same product shown above).

For the cis-but-2-ene, bromine addition across the double bond yields:

Both reactions happen via trans addition via the bromonium intermediate.
Also order of the products could be reversed.
2S,3S could be P and 2R,3R could be O as well. It is a general assignment.

Clearly, O and P are a pair of enantiomers.
(M & O) and (N & P) are two pairs of diastereomers