Since the structural isomers refers to the compounds that have same molecular formula but different arrangement of atoms or groups within the molecule. Based on this, following are the structural isomers for $C _{6} H _{14}$ :
$CH _{3}- CH _{2}- CH _{2}- CH _{2}- CH _{2}- CH _{3}$
$n$ -hexane
$H_3C - \underset{\overset{|}{C}H_3}{CH} - CH_2 - CH_2 - CH_3$
$2$ - Methyl pentane
$H_3C - CH_2 - \underset{\overset{|}{C}H_3}{CH} - CH_2 - CH_3$
$3$ - Methyl pentane
$2,3$ -Dimethyl butane
