Question

What happens in this reaction and why? hept-3-yne + Br2 -->

Answer 1

Here we have to explain and predict the product of the reaction between hept-3-yne and bromine (Br₂)

The reaction between hept-3-yne and bromine produces trans-3,4-dibromo-3-heptene.

The reaction between the unsaturated hydrocarbon with halogen remove the unsaturation in the molecule and produces di halo compound. The reaction proceed through the formation of bromonium ion.

In this reaction as the unsaturation present in the middle of the alkyl chain i.e. hept-3-yne. The reaction will stop after the formation of di-halo compound with one double bond as shown in the figure.

The product will be exclusively trans product as the bromine is a bulky group and the formation of bromonium ion (intermediate) will be one side of the unsaturated compound.