Question

Which of the following reactions gives a meso compound as the main product?

• A.
• B.
• C.
• D.

Answer 1

The correct option is A

Halogens like Br, Cl and I add up to alkenes to form vicinal dihalides. Addition of halogens to alkenes​ is an example of electrophilic​ addition reaction. Addition of two substituents to​ multiple bonded C atoms from the ​opposite sides of the multiple bond is known as anti addition. When anti addition takes place to an symmetrical trans alkene, then meso compound is formed.
Here in option (a) and (b), trans alkenes are present but only in option (a) $B{r}_2$ addition is there. Hence, option (a) will produce meso compound.