question_answer

Which of the following compounds will give a yellow precipitate with iodine and alkali? [AIPMT (M) 2012]

A) Acetophenone

B) Methyl acetate

C) Acetamide

D) 2-hydroxypropane

Correct Answer: D

Solution :

[d] Out of the given compounds, only\[C{{H}_{3}}-\underset{OH}{\mathop{\underset{|}{\mathop{CH}}\,}}\,-C{{H}_{3}}\](2-hydroxyprepane)gives yellow precipitate with iodine and alkali (iodoform test).But

\[C{{H}_{3}}-COO-C{{H}_{3}}\](methyl acetate),

\[C{{H}_{3}}-CO-N{{H}_{2}}\](accetamide),

do not perform this test because \[\alpha -H\]is not active due to +M effect of nearby group.

\[C{{H}_{3}}-\underset{OH}{\mathop{\underset{|}{\mathop{CH}}\,}}\,-C{{H}_{3}}+4{{I}_{2}}+6NaOH\]\[\xrightarrow{{}}\underset{\begin{smallmatrix}  Iodoform \\  (yellow\,ppt) \end{smallmatrix}}{\mathop{CH{{I}_{3}}}}\,\downarrow +C{{H}_{3}}COONa+5NaI+5{{H}_{2}}O\]