Pentane is a straight-chain hydrocarbon with the molecular formula C5H12. How many additional structural isomers can be constructed using this molecular formula?

3

Explanation:

Firstly, we need to define the phenomenon know as isomerism. It is a phenomena in which 2 or more organic compounds have the same molecular formula but different structural arrangements.

In this special case of pentane, we are looking at other compounds whose molecular formulas are also C5H12 but have a different structure from that of pentane. It must be noted that two isomers might belong to the same homologous series or belong to a different homologous series entirely.

The first isomer is 2-methylbutane also known trivially as isopentane. It has the same molecular formula as said earlier with a methyl group substituted for a hydrogen atom on the second carbon of the principal chain of the molecule.

The second one is n-pentane itself. This is the normal straight chain pentane in its linear form.

The third one is 2-ethylpropane or dimethylpropane trivially knows as neopentane.