#### 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.

Butane: $C_4H_{10}$

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.