Final answer:
A pair of compounds classified as enantiomers are non-superimposable mirror images but have the same molecular formula. Two substances can have the same name but be different compounds if they are stereoisomers. A carbon-carbon multiple bond is a functional group that affects a molecule's chemical properties. So option (2) is correct.
Step-by-step explanation:
To classify a pair of compounds as either being the same compound or enantiomers, one must examine their three-dimensional structure. Enantiomers are stereoisomers that are non-superimposable mirror images of each other. This means that while they have the same molecular formula and connectivity of atoms (same systematic name), their arrangement in space is such that one is the mirror image of the other and cannot be overlaid onto the original molecule, much like left and right hands.
Addressing the first conceptual problem, two substances can indeed have the same systematic name and be different compounds if they are stereoisomers, like enantiomers or diastereomers, which have the same connectivity but a different spatial arrangement of atoms.
For the second conceptual problem, a carbon-carbon multiple bond (double or triple bond) is indeed considered a functional group in organic chemistry. Functional groups are specific groupings of atoms within molecules that have their unique chemical properties. A carbon-carbon multiple bond affects the molecule's reactivity and is involved in reactions characteristic of such groups.