Question

Write the IUPAC name of isoprene.

Answer 1

Structure and IUPAC Name of Isoprene

The molecular structure of isoprene is given as:

\[ \text{CH}_2 = \text{C}(\text{CH}_3) - \text{CH} = \text{CH}_2 \]

Step 1: Identify the Longest Chain

The longest continuous carbon chain that includes both double bonds contains 4 carbon atoms. Hence, the parent hydrocarbon is buta-1,3-diene.

\[ \text{C}_1 = \text{CH}_2,\quad \text{C}_2 = \text{C},\quad \text{C}_3 = \text{CH},\quad \text{C}_4 = \text{CH}_2 \]

Step 2: Numbering the Chain

Numbering starts from the end that gives the double bonds the lowest locants. Therefore, the double bonds are at carbons 1 and 3.

\[ \text{Buta-1,3-diene} \]

Step 3: Identify Substituents

A methyl group (\(\text{-CH}_3\)) is attached to the second carbon atom of the chain.

\[ \text{Substituent: } -\text{CH}_3 \text{ on C}_2 \]

Step 4: Combine the Name

Putting it all together:

\[ \textbf{2-methylbuta-1,3-diene} \]

Final Answer:

The IUPAC name of isoprene is \[ \boxed{\text{2-methylbuta-1,3-diene}} \]