Q. 8-8-66E-b - Organic Chemistry (Mcmurry)

Question

How would you distinguish between the following pairs of compounds using simple chemical tests? Tell what you would do and what you would see. 

(b) 2-Hexene and benzene

Step-by-Step Solution

Answer

2-Hexene shows reaction with  ${\mathrm{Br}}_2/{\mathrm{CCl}}_4$and also shows decolorization, but benzene does not show a reaction  ${\mathrm{Br}}_2/{\mathrm{CCl}}_4$

Reaction of 2-Hexene with Br 2 / CCl 4

2-Hexene is an unsaturated compound due to the presence of a double bond hence on reaction with ${\mathbf{Br}}_{\mathbf{2}}\mathbf{/}{\mathbf{CCl}}_{\mathbf{4}}$ show bromination.  It forms 1,2 diol and shows decolorization.

Reaction of benzene with Br 2 / CCl 4

Benzene is the aromatic compound that only show bromination in the presence of ${\mathrm{FeCl}}_3/{\mathrm{AlCl}}_3$ which provide the Br electrophile to the benzene for bromination. Hence, no reaction occurs.