Answer
a) The structural isomers of $C_{8}H_{18}$ having root name 'heptane' are:
2-methylheptane, 3-methylheptane & 4-methylheptane
b) The structural isomer of $C_{8}H_{18}$ having root name 'butane' is:
2,2,3,3-tetramethylbutane.
All structural formulas are written below:
Work Step by Step
a) Draw 7 C in a straight chain. Now, add substituent methyl group at C2 position and the remaining valency of C atoms is filled with H to get 2-methylheptane. Similarly, if we add methyl group at C3 or C4 position we get 3-methylheptane and 4-methylheptane respectively.
b) Draw 4 C in straight chain. Now, add two methyl groups at C2 and two methyl groups at C3 position to get 2,2,3,3-tetramethylbutane.
