Question

Which of the following compounds will give a yellow precipitate with iodine and alkali? (1) 2-hydroxy propane (2) Acetophenone (3) Methyl acetate (4) Acetamide

• A. 1, 2 and 3 are correct.
• B. 1 and 2 are correct.
• C. 2 and 4 are correct.
• D. 1 and 3 are correct.

Answer 1

Answer: (B)

A compound which contains either $C{H}_3\underset{\begin{array}{c}|\\ OH\end{array}}{\mathrm{CH}}$ or $C{H}_3\stackrel{\begin{array}{c}O\\ ||\end{array}}{C}$ group, gives yellow precipitate of iodoform with $I_2$ and alkali. $\underset{2-hydroxypropane}{C{H}_3-\stackrel{\begin{array}{c}OH\\ |\end{array}}{\mathrm{CH}}-C{H}_3}\underset{-NaCl,-H_{2}O}{\overset{NaOH/I_2}{\to }}$ $\underset{iodoform}{CH{I}_3}+C{H}_{3}COONa$
$Methylacetate\stackrel{NaOH/I_2}{\to }Noreaction$ $Acetamide\stackrel{NaOH/I_2}{\to }Noppt$
$\therefore$ Only 2-hydroxy propane and acetophenone give positive iodoform test.