What is the IUPAC name for an alkene with six carbon atoms and a double bond starting at the first carbon?

The IUPAC name for an alkene with six carbon atoms and a double bond starting at the first carbon is hex-1-ene. In the nomenclature of alkenes, the general rule is to indicate the position of the double bond in the name. The "hex" prefix denotes that there are six carbon atoms in the longest continuous carbon chain.

The "-1-ene" suffix specifies that the double bond begins at the first carbon of the chain. Since the double bond is at the first carbon, it is customary to label it as "1" to clearly indicate its location and since the position "1" is understood when saying hex-1-ene, this designation provides clarity in structural identification.

In the provided options, hex-2-ene would incorrectly suggest that the double bond starts at the second carbon, which does not match the given condition. Simply stating hexene does not provide the specific location of the double bond, which is insufficient for proper nomenclature. Pent-1-ene is also incorrect as it indicates a five-carbon chain, which does not correspond to the six carbon atoms of the specified molecule. Thus, the most precise and correct representation of the compound is hex-1-ene.