Question

Which of the following are correct structural isomers of butane?

(A) (i) and (iii)            (B) (ii) and (iv)
(C) (i) and (ii)             (D) (iii) and (iv)

Answer 1

(C) (i) and (ii)

Structural isomers are compounds having the same molecular formula but different structures. The molecular formula of butane is C₄H₁₀. Structure (i) and (ii) have same molecular formula - C₄H₁₀, only the structures are different. Hence, they are structural isomers of butane. Structure (iii) and (iv) have molecular formula - C₄H₈ and hence, they are not structural isomers of butane.