Which of the following is the IUPAC name for C2H5OH?

The compound C2H5OH is recognized as ethanol in IUPAC nomenclature. To understand why this is the correct name, we can break down the structure and the naming conventions applied.

Ethanol consists of two carbon atoms (as indicated by "C2"), which signifies that its longest carbon chain has two carbons, identifying it as an ethyl group (C2H5). The "OH" group shows that it is an alcohol, and in organic chemistry, the suffix for alcohols is typically "-ol."

When naming alcohols following IUPAC rules, you start with the longest carbon chain that includes the hydroxyl group. Since there are two carbons, you employ the prefix "eth-" for the carbon chain, combined with the alcohol suffix "-ol," resulting in "ethanol."

The other names provided refer to different compounds. Methanol corresponds to a single carbon alcohol (C1H3OH), propanol is for three carbon alcohol (C3H7OH), and butanol represents four carbon alcohols (C4H9OH). Thus, they do not match the structure of C2H5OH, affirming that ethanol is the appropriate nomenclature.