The pair of molecules that are metamers among the following is:

Solution & Explanation

\textbf{Answer:} (D) \ce{CH3OCH2CH2CH3} and \ce{CH3CH2OCH2CH3} \textbf{Solution:} Metamers are compounds with the same molecular formula and the same functional group, differing in the number of carbon atoms (alkyl groups) attached on either side of the functional group. This is characteristic of ethers, amines, ketones, etc. Methyl $n$-propyl ether \ce{CH3-O-CH2CH2CH3} and diethyl ether \ce{CH3CH2-O-CH2CH3} both have the molecular formula \ce{C4H10O} and the same ether functional group, but the alkyl groups on the two sides differ (methyl/propyl vs ethyl/ethyl). Hence they are metamers. Option (A) is a pair of positional/functional isomers (alcohols), (B) is a pair of chain isomers (alkanes), and (C) is a pair of chain/positional isomeric alcohols — none of these is metamerism.