Chemistry - STRUCTURAL ISOMERISM Question with Solution | TestHub

Metamers are the isomers having the same molecular formula but different alkyl groups on two sides of functional groups. Positional isomers are constitutional isomers with the same carbon skeleton and will have the same functional group.  Functional isomers are structural isomers that have the same molecular formula (that is, the same number of atoms of the same elements), but the atoms are connected in different ways so that the groupings are dissimilar. Tautomerism is a phenomenon where a single chemical compound tends to exist in two or more interconvertible structures that are different in terms of the relative position of one atomic nucleus which is generally the hydrogen.

A. Propanamine and N- Methylethanamine $({\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{CH}}_2{\mathrm{NH}}_2 \text{and} {\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{NHCH}}_3)$

B. Hexan-$2$-one Hexan-$3$-one 

C. Ethanamide Hydroxyethanimine

D. o-Nitrophenol p-nitrophenol

So, the correct option is D.