How many structural isomers does #C_6H_14# have?
There are five structural isomers of
A 6-carbon chain
A 5-carbon chain with a methyl group
This gives two isomers: 2-methylpentane and 3-methylpentane.
A 4-carbon chain with two methyl groups
This gives two isomers: 2,2-dimethylbutane and 2,3-dimethylbutane.
That's all the possibilities.
So, there are five structural isomers of