Which compounds are isomers?
A. Ethane and ethanol.
B. Methanol and methanal.
C. 1-propanol and 2-propanol.
D. Methanoic acid and ethanoic acid.
By definition isomers have the same molecular formula but different structural formulas. Choice 3 compounds have the same molecular formula but the -OH group is located on the first or second carbon atoms. The other choices do not have the same molecular formulas.