Number of molecules from below which cannot give iodoform reaction is : Ethanol, Isopropyl alcohol, Bromoacetone, 2-Butanol, 2-Butanone, Butanal, 2-Pentanone, 3-Pentanone, Pentanal and 3-Pentanol.
- 4
- 3
- 5
- 2
Answer
(1) 4
Solution
Iodoform test is given by compounds having CH3CO- group or CH3CH(OH)- group (oxidised to CH3CO- by NaOI), including ethanol.
Give the test: ethanol (CH3CH2OH), isopropyl alcohol (CH3CH(OH)CH3), bromoacetone (CH3COCH2Br), 2-butanol (CH3CH(OH)CH2CH3), 2-butanone (CH3COCH2CH3), 2-pentanone (CH3COCH2CH2CH3).
Do not give the test: butanal (CH3CH2CH2CHO), 3-pentanone (CH3CH2COCH2CH3), pentanal (CH3(CH2)3CHO), 3-pentanol (CH3CH2CH(OH)CH2CH3) — none has a CH3CO- or CH3CH(OH)- unit.
∴ Number of molecules that cannot give the iodoform reaction = 4
Answer: (1)