Compound which posses same molecular formula but differ in each other in the structure of carbon chain is ?

Two or more compounds are called structural isomers if they possess the same molecular formula but different structural formulas.  

Explanation:

Two compounds are considered structural isomers if their molecular formulas are the same while they differ in their structural formulas.

For example, the molecular formula represents both butane and methylpropane. However, the two compounds differ in their structural formula. (See the structural formulas in the diagram attached.)

Due to the difference in the structures of structural isomers, there's a good chance that they will show different chemical and physical properties. For example, the melting point of butane is higher than that of methylpropane. The straight-chain shape of butane allows its molecules to be stacked close to each other. That allows for greater intermolecular forces and, therefore, a higher melting point.