Which stereoisomer of 3-hexene forms a meso compound when it reacts with #Br_2# ?
trans-Hex-3-ene forms a meso compound when it reacts with bromine.
The bromination of an alkene involves the formation of an intermediate cyclic bromonium ion, followed by the anti-addition of a bromide ion to form the product.
The rigidity of the ring controls the stereochemistry of the reaction.
This means that the bromination of a trans alkene gives a meso dibromide.
For example, the bromination of trans-but-2-ene yields a meso compound.
Similarly, the bromination of hex-3-ene gives meso-2,3-dibromohexane as the product.
These two structures are superimposable on each other, so the product is a meso compound.