lodoform test can be used to distinguish between:
Correct answer: D. all of the above
- A. ethanol and methanol
- B. acetaldehyde and methanal
- C. acetone and diethyl ketone
- D. all of the above
Explanation
The iodoform test relies on the reaction of a compound with excess iodine and sodium hydroxide to form iodoform (CHI₃), a yellow crystalline solid with a distinctive smell. This reaction occurs with compounds containing a methyl ketone group (RCOCH₃) or a secondary alcohol group (RCH(OH)CH₃) adjacent to a α-hydrogen atom (hydrogen atom attached to the carbon next to the carbonyl or hydroxyl group).Therefore, the iodoform test can be used to distinguish between:(a) Ethanol and methanol: Ethanol (CH₃CH₂OH) gives a positive test due to the presence of a secondary alcohol group (CH₂CH(OH)), while methanol (CH₃OH) lacks the required α-hydrogen and gives a negative test.(b) Acetaldehyde (CH₃CHO) and methanal (CH₂O): Acetaldehyde gives a positive test due to the methyl ketone group (CH₃CO), while methanal lacks both the methyl ketone and α-hydrogen, leading to a negative test.(c) Acetone (CH₃COCH₃) and diethyl ketone (CH₃CH₂COCH₂CH₃): Acetone shows a positive test due to the presence of two methyl ketone groups.
Last updated
About Aldehydes and Ketones
Aldehydes and ketones contain the polar carbonyl group, but aldehydes are generally more readily oxidised and more reactive than ketones. Coverage includes preparation by oxidation or reduction routes, nucleophilic addition of reagents such as hydrogen cyanide and bisulfite, and tests that distinguish aldehydes from ketones.
Practise Aldehydes and Ketones
679 free Aldehydes and Ketones MCQs from Chemistry, each with the correct answer and an explanation. Unlimited attempts, no account needed.
Exams that ask Chemistry questions like this
Chemistry is on 12 papers prepared for on TestUstad, and all of them draw the same bank, so this question is worth knowing for every one of them.