Question

Iodoform test is not given by

• A. $ 2 $ -pentanon
• B. ethanol
• C. ethanal
• D. $ 3 $ -pentanone

Answer 1

Answer: (D)

Iodoform test is given by compounds which have $(CH_3 — CO—)$ group or





group, Hence, 2 -pentanone, $CH _{3} CHO$ and $C _{2} H _{5} OH$


give this test. But 3-pentanone $\left( CH _{3} CH _{2} COCH _{2} CH _{3}\right)$ does not give iodoform test.


$\underset{\text{2 - pentanone}}{(CH_3COCH_2CH_2CH_3)} + 3I_2 + 4NaOH \rightarrow $

$\underset{\text{iodoform (yellow ppt)}}{CHI_3 \downarrow} + CH_3CH_2CH_2COONa + 3NaI + 3H_2O$

$\underset{\text{ethanal}}{CH_3 - CHO} + 3I_2 + 4NaOH \to$

$\underset{\text{iodoform (yellow ppt.)}}{CHI_3 \downarrow} + HCOONa + 3NaI + 3H_2O$

$\underset{\text{ethanal}}{C_2H_5OH} + 4I_2 + 6NaOH \to$

$\underset{\text{iodoform(yellow ppt.)}}{CHI_3\downarrow}+HCOONa + 5NaI + 5H_2O$

$\underset{\text{3 - pentanone}}{CH_3 - CH_2 - CO - CH_2 - CH_3+ I_2}$

$+ NaOH \to $ No reaction