Which group gives a yellow precipitate of triiodomethane when warmed with alkaline aqueous iodine?
Correct answer: D. Methyl ketone group, CH3COR
- A. An amide group, CH3CONH2
- B. Ethyl ketone group, C2H5COR
- C. A primary alcohol group as in propanol, CH3CH2CH2OH
- D. Methyl ketone group, CH3COR
Explanation
In the case of ethanal, methyl ketone or a secondary alcohol with a methyl group in the alpha position, a pale yellow precipitate of iodoform or triiodomethane is formed.
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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.
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