Question

Which one of the following is obtained when acetone is treated with bleaching powder?

• A. $C{H}_{3}Cl$
• B. $C{H}_{2}C{l}_2$
• C. $CHC{l}_3$
• D. $CC{l}_4$

Answer 1

Answer: (C)

When acetone is treated with bleaching powder, then chloroform is formed.
Bleaching powder $\left(CaOC{l}_2\right)$ supplies the necessary chlorine and slaked lime (calcium hydroxide) for the reaction.
$\underset{\text{bleaching powder}}{CaOC{l}_2}+H_{2}O⟶\underset{\text{slaked lime}}{Ca(OH{)}_2+C{l}_2}$
Chlorine so obtained acts as a chlorinating agent. It reacts with acetone and gives trichloroacetone which formed chloroform on hydrolysis.
$\underset{\text{acetone}}{C{H}_{3}COC{H}_3}+3C{l}_2⟶\underset{\text{trichloroacetone}}{C\cdot C{l}_3\cdot COC{H}_3}+3HCl$
$Ca(OH{)}_2+2CC{l}_{3}COC{H}_3⟶\underset{\text{ chloroform }}{2CHC{l}_3}+\underset{\text{calcium acetate}}{{\left(C{H}_{3}COO\right)}_{2}Ca}$
This is the laboratory method of chloroform preparation.
Ethyl alcohol also gives chloroform with bleaching powder. In this reaction bleaching powder functions as oxidising, chlorinating and hydrolysing agent.