What is the IUPAC name for a three-carbon chain with a double bond between C1 and C2?

The correct IUPAC name for a three-carbon chain that has a double bond between the first and second carbon atoms is propene.

In organic nomenclature, the name reflects both the number of carbon atoms in the longest continuous chain and the presence of functional groups, such as double or triple bonds. In this case, the molecule has three carbon atoms, which corresponds to the prefix "prop-." Since there is a double bond in the chain, the suffix "-ene" is used, indicating the presence of the double bond.

Therefore, combining these parts, we establish the IUPAC name as propene. The chain's structure can be denoted as C1=C2-C3, confirming the name accurately describes its features.

Other terms listed do not fit this description: "butene" would indicate a four-carbon chain, "ethylene" refers specifically to a two-carbon alkene, and "alkane" is a general term for saturated hydrocarbons without double or triple bonds, which does not apply here.