Question

Prove that the minimum number of carbon atoms in ketone to show metamerism is 5.

Answer 1

Dear Student,

Metamers are compounds having same molecular formula ​but different distribution of alkyl groups. In ketones, this can be done by different distribution of alkyl groups around the functional group -O-.
Now, the simplest ketone is acetone i.e. CH₃COCH₃. This can be arranged only in this manner,
Next is CH₃CH₂COCH₃, or we can say CH₃COCH₂CH₃. Both these compounds are identical, therefore no metamer is formed.
CH₃CH₂COCH₂CH₃ can be written as CH₃COCH₂CH₂CH₃ which has different alkyl arrangement and therefore, both the compounds are metamers. Hence, minimum 5 carbon atoms are required to show metamerism in ketones.