How many structural isomers can you draw for pentane?

Structural isomers are compounds that have the same molecular formula but different structures.

Now, the molecular formula of pentane is ${\mathrm{C}}_5{\mathrm{H}}_{12}$. Pentane has three structural isomers.  Thus, its structural isomers are -

• n-pentane: In this, all carbons are attached in a straight chain. 
• 2-Methylbutane- It has one carbon as a methyl group on carbon-2 with four carbon straight chains. It is also called isopentane.
• 2,2-Dimethylpropane- It has 2 methyl groups at carbon 2a  with a three-carbon straight chain. It is also called neo-pentane.

Therefore, pentane ahs 3-structural isomers: n-pentane, 2-methylbutane(isopentane) and dimethylpropane(neopentane).

Hence, the correct option is (B).