Question

What happen when bromine attack on the nitrobenzene?

Answer 1

H2C = CH - CH2 - C -= CH + 2Br2

If Br2 is added, the result is a two-step reaction.

1. BrH2C - CBrH - CH2 - BrC = CBrH

( + 2Br2)

2. BrH2C - CBrH - CH2 - Br2C - CBr2H

Reactions of the alkynes with halogens exactly follows the pattern seen for the alkenes i.e. this is an Electrophilic Addition Reaction so it is more likely the π electrons act as a nucleophile, attacking the bromine.

The product depends on the state of the bromine used. Using pure bromine in liquid stage, the reaction takes straight path to No. 2, while an aqueous solution of bromine first produces step 1 in slow reaction then ultimately step 2.