Chemistry - STRUCTURAL ISOMERISM Question with Solution | TestHub

Structural isomers of butane must have the molecular formula C₄H₁₀.

(A) represents n-butane (CH₃–CH₂–CH₂–CH₃), so it is a valid isomer.

(B) represents isobutane (2-methylpropane), the second structural isomer of C₄H₁₀.

(C) has incorrect carbon valency/connectivity and does not represent a valid C₄H₁₀ structure.

(D) is a four-membered ring (cyclobutane, C₄H₈), so it is not an isomer of butane.