All five hexane constitutional isomers have the same molecular formula, C6H14, and the same molecular weight, 86. However, each one of the hexanes has a unique boiling point.

Introduction:
Hexane is an organic compound with the molecular formula C6H14. It belongs to the class of alkanes, which are hydrocarbons with only single bonds between carbon atoms. Structural isomers are compounds with the same molecular formula but different structural arrangements.

Explanation:
There are several ways to draw structural isomers for hexane. Let's explore them in detail:

Straight-Chain Isomers:
The simplest form of hexane is a straight-chain isomer. Here, all six carbon atoms are arranged in a continuous straight line, with each carbon atom bonded to two hydrogen atoms. There is only one straight-chain isomer for hexane.

Branched-Chain Isomers:
Branched-chain isomers are formed when one or more carbon atoms deviate from a straight line, creating branches. Hexane can have multiple branched-chain isomers:

1. 2-Methylpentane: In this isomer, a methyl group (-CH3) is attached to the second carbon atom of the straight chain.
2. 3-Methylpentane: Here, the methyl group is attached to the third carbon atom of the straight chain.
3. 2,2-Dimethylbutane: This isomer has two methyl groups attached to the second carbon atom and the adjacent carbon atom (fourth carbon) of the straight chain.
4. 2,3-Dimethylbutane: In this case, one methyl group is attached to the second carbon atom, and the other is attached to the third carbon atom of the straight chain.

Cyclic Isomers:
Hexane can also form cyclic isomers by creating a ring structure. There are two cyclic isomers of hexane:

1. Cyclohexane: All six carbon atoms form a ring, and each carbon atom is bonded to two hydrogen atoms.
2. Methylcyclopentane: In this isomer, a methyl group is attached to one of the carbon atoms in the cyclopentane ring.

Total Number of Isomers:
To summarize, there are a total of nine structural isomers for hexane: one straight-chain isomer, four branched-chain isomers, and two cyclic isomers.

Conclusion:
Hexane exhibits a variety of structural isomers due to its molecular formula and the ability of carbon atoms to form different arrangements. These isomers have distinct physical and chemical properties, making them important in various applications such as solvents, fuels, and chemical intermediates. Understanding the different isomers of hexane is essential in organic chemistry as it provides insight into the diverse nature of organic compounds.