Question

Which of the following statement is correct?

• A. Formaldehyde on heating with $I_2$ and alkali gives yellow ppt.
• B. Ethanol is the only primary alcohol which gives haloform reaction.
• C. All secondary alcohol gives haloform reaction.
• D. All ketones gives haloform reaction.

Answer 1

The correct option is B Ethanol is the only primary alcohol which gives haloform reaction.

Any compounds containing the $C{H}_{3}C=O$ group or the $C{H}_{3}CH\left(CO\right)$ group give a positive result with the iodoform test. When $I_2$ and $NaOH$ is added to a compound containing one of these groups, a pale yellow precipitate of iodoform(triiodomethane) is formed.
The correct statement is that ethanol is the only primary alcohol which gives haloform. $C{H}_{3}C{H}_{2}OH\underset{+NaOH}{\overset{+I_2}{\to }}C{I}_{3}CHO\stackrel{+NaOH}{\to }CH{I}_3\left(Iodoform\right)+HCOONa$