In the reaction : `CH_(2) = CH - CH = CH_(2) + Br_(2) overset(-40^(@)C)rarr` the predominant product is :

Options

A. 3, 4-Dibromo but-1-ene
B. 1, 4-Dibromo but-2-ene
C. 1, 2, 3, 4-Tetrabromobutane
D. 2, 4-Dibromo but-2-ene

Answer

B

Explanation

The addition to conjugate diene at `-40^(@)C` gives 1, 4-addition product.
`CH_(2) = CH - CH = CH_(2) + Br_(2) overset(-40^(@)C)rarr underset(Br)underset(|)(CH_(2))-CH = CH - CH_(2)Br`
At low temperatures `(-80^(@)C)` it gives 1, 2-addition product.