Which of the following compounds can give positive iodoform test when treated with aqueous KOH solution followed by potassium hypoiodite.
- CH3CH2- O \|C-CH2CH3
- [figure]
- CH3CH2- Cl | Cl |C-CH3
- CH3CH2CH2CHO
Answer
(3) CH3CH2- Cl | Cl |C-CH3
Solution
Iodoform test needs a CH3CO- (or CH3CH(OH)-) group in the compound formed after treatment with aq. KOH.
(3): a gem-dichloride is hydrolysed by aq. KOH to a ketone:
CH3CH2- Cl | Cl |C-CH3 aq. KOH CH3CH2- O \|C-CH3
KOI CH3CH2COOK + yellowCHI3
So (3) gives the test.
(1): pentan-3-one has no CH3CO- group, so (1) does not.
(2): the epoxide opens to CH3CH2CH(OH)CH2OH, which has no CH3CH(OH)- group, so (2) does not.
(4): butanal has no CH3CO- group, so (4) does not.
Answer: (3)