Given the following structures, select the correct IUPAC name for the compound: ${\mathrm{CH}}_3$${\mathrm{CH}}_2$C=CH${\mathrm{CH}}_3$.

• A. $1$-Butene
• B. $2$-Butene
• C. Isobutene
• D. Cyclobutene

Answer: (B)

Verified step by step guidance

1. Identify the longest carbon chain that contains the double bond. In this case, the chain has 4 carbons, so the base name is 'butene'.
2. Number the carbon chain from the end nearest the double bond to give the double bond the lowest possible number. This means numbering from the end that places the double bond at carbon 1 or carbon 2.
3. Determine the position of the double bond based on the numbering. If the double bond starts at carbon 1, the name is '1-butene'; if it starts at carbon 2, the name is '2-butene'.
4. Check for any branching or substituents that might change the name. Since the structure is a straight chain with no branches, no additional prefixes are needed.
5. Compare the options given with the correct IUPAC naming rules: '1-butene' and '2-butene' are positional isomers, 'isobutene' refers to a branched isomer (2-methylpropene), and 'cyclobutene' is a cyclic compound. Select the name that correctly corresponds to the position of the double bond in the given structure.