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)
Solution: Structural isomers: two or more organic compounds having the same molecular formulas but different structures.
Structure (i) is n-butane. It is a structural isomer of butane.
Structure (iii) is iso-butane. It is a structural isomer of butane.
Other structures, i.e., (ii) and (iv) have different molecular formula, hence incorrect
Therefore, option (c) is correct.