Question

Analyze the compound $CH_2CH_2CH=CHCH_3$. What is the IUPAC name for this compound, and what functional group is present?

• A. 3-pentene; alkane
• B. 2-butene; alkene
• C. 2-pentene; alkene
• D. 3-butene; alkyne

Answer 1

Answer: (C)

2-pentene; alkene

Answer 2

The compound $CH_2CH_2CH=CHCH_3$ is interpreted as $CH_3CH_2CH=CHCH_3$. The longest carbon chain containing the double bond has 5 carbons, so the root is "pent". The presence of a carbon-carbon double bond indicates it's an alkene, so the suffix is "-ene". Numbering the chain from the end that gives the double bond the lowest possible number (from right to left) places the double bond at position 2. Thus, the IUPAC name is 2-pentene, and the functional group is an alkene.