Which of the following pairs has compounds that are isomers?

Isomers are compounds that have the same molecular formula but different structural arrangements. To determine which pairs have compounds that are isomers, we need to compare the structures of the compounds in each pair. - Propanal and propanone are functional isomers. They have the same molecular formula, C3H6O, but different functional groups. Propanal has an aldehyde functional group while propanone has a ketone functional group. Therefore, they are isomers. - Ethanoic acid and ethylmethanoate are not isomers. They have different molecular formulas: C2H4O2 and C3H6O2, respectively. - Ethanoic acid and ethane-1,2-diol are not isomers. They have different molecular formulas: C2H4O2 and C2H6O2, respectively. - 2-methylbutane and 2,2-dimethylbutane are structural isomers. They have the same molecular formula, C6H14, but different structural arrangements. Therefore, they are isomers. Thus, the pairs that have compounds that are isomers are propanal and propanone, and 2-methylbutane and 2,2-dimethylbutane.