Question

$C{H}_3\stackrel{\stackrel{O}{\parallel }}{C}C{H}_3$ can be converted into $C{H}_3\stackrel{\stackrel{O}{\parallel }}{C}OH$ by following methods
I. $C{H}_3\stackrel{\stackrel{O}{\parallel }}{C}C{H}_3\underset{△,H^{+}}{\stackrel{I_2/NaOH}{\to }}$
II. $C{H}_3\stackrel{\stackrel{O}{\parallel }}{C}C{H}_3\stackrel{C{r}_2{O}_7^{2-}/H^{+}}{\to }$
III. $C{H}_3\stackrel{\stackrel{O}{\parallel }}{C}C{H}_3\stackrel{Ag(N{H}_3{)}_2^{+}}{\to }$

Which method is/are most effective?

• A. I, III
• B. II, III
• C. I, II
• D. I, II, III

Answer 1

Answer: (C)

I, II

(I) Methyl ketones $\left(C{H}_3\stackrel{\stackrel{O}{\parallel }}{C}R\right)$ react rapidly with halogens, $(C{l}_2,B{r}_2,I_2)$ in presence of alkali to form haloform.
$C{H}_3\stackrel{\stackrel{O}{\parallel }}{C}C{H}_3+3I_2+4NaOH\to C{H}_3\stackrel{\stackrel{O}{\parallel }}{C}-ONa+CH{I}_3+3Nal+3H_{2}O$
$C{H}_3\stackrel{\stackrel{O}{\parallel }}{C}-ONa+H^{+}\underset{-N{a}^{+}}{\stackrel{\Delta }{}}C{H}_3\stackrel{\stackrel{O}{\parallel }}{C}OH$

(II) Stronger oxidising agents oxidise ketones to carboxylic acids.
$C{H}_3\stackrel{\stackrel{O}{\parallel }}{C}C{H}_3\stackrel{K_{2}C{r}_2{O}_7+H_{2}S{O}_4}{\to }C{H}_3\stackrel{\stackrel{O}{\parallel }}{C}H+H\stackrel{\stackrel{O}{\parallel }}{C}OH$

(III) Tollen's reagent (ammonical silver nitrate solution), being weak oxidising agent cannot reduce acetone into acetic acid.
$C{H}_3\stackrel{\stackrel{O}{\parallel }}{C}C{H}_3+\left[Ag\right(N{H}_3{)}_2^{+}]\to Noreaction$