Q25 / 160 · TS EAMCET 2010 · Chemistry
Which one of the following gives yellow precipitate with iodine and $\mathrm{NaOH}$ solution?
- Correct answerA$\mathrm{CH}_3-\mathrm{CHO}$
- B$\mathrm{C}_6 \mathrm{H}_5 \mathrm{COC}_6 \mathrm{H}_5$
- C$\mathrm{HCHO}$
- D$\mathrm{CH}_3 \mathrm{OH}$
Solution
Alcohols containing $\mathrm{CH}_3 \mathrm{CH}(\mathrm{OH})-$ group and carbonyl compounds containing $\mathrm{CH}_3 \mathrm{CO}-$ group give yellow precipitate with iodine and $\mathrm{NaOH}$ solution. This reaction is called iodoform test.
Thus, $\mathrm{CH}_3 \mathrm{CHO}$ due to presence of $\mathrm{CH}_3 \mathrm{CO}$ group gives yellow ppt with $\mathrm{I}_2$ and $\mathrm{NaOH}$.
$\mathrm{CH}_3 \mathrm{CHO}+3 \mathrm{I}_2+4 \mathrm{NaOH} \longrightarrow \mathrm{CHI}_3 +\mathrm{HCOONa}+3 \mathrm{NaI}+2 \mathrm{H}_2 \mathrm{O}$
Hence, the correct answer is option: 'A'.