Which of the following is the correct IUPAC name for the compound with the structure ${\mathrm{CH}}_2$=${\mathrm{CH}}_2$–${\mathrm{CH}}_2$–${\mathrm{CH}}_3$?

• A. $2$-Butene
• B. Ethene
• C. $1$-Butene
• D. But-1-ene

Answer: (C)

Verified step by step guidance

1. Identify the longest carbon chain that contains the double bond. In this molecule, the chain has 4 carbon atoms, so the base name is 'butene'.
2. Number the carbon chain starting from the end nearest to the double bond to give the double bond the lowest possible number. This means numbering from the end where the double bond starts at carbon 1.
3. Determine the position of the double bond based on the numbering. If the double bond starts at the first carbon, the correct locant is 1, making it 'but-1-ene' or '1-butene'.
4. Understand that '2-butene' indicates the double bond starts at the second carbon, which is not the case here, and 'ethene' refers to a two-carbon alkene, which does not match the four-carbon chain.
5. Conclude that the correct IUPAC name is 'but-1-ene' (or '1-butene'), reflecting a four-carbon chain with a double bond starting at carbon 1.