Final answer:
The molecular formula C5H12 has three structural isomers: n-pentane with a straight chain, isopentane with a branched chain, and neopentane with a compact, highly branched structure.
Step-by-step explanation:
The compound with the molecular formula C5H12 has three isomers. These are the different ways the carbon atoms can be arranged to still have the same molecular formula, known as structural isomers.
The second isomer is isopentane (also known as methylbutane), which has a chain of four carbon atoms with a methyl group (-CH3) attached to the second carbon.
The third isomer is neopentane (also known as dimethylpropane), which has a central carbon atom with four methyl groups attached to it - a very compact structure.
These isomers differ not only in their names but also their physical properties, like boiling points and melting points, due to having different structures.