Question

Draw structure of isoprene unit of natural rubber.

Hint:

Remember: Natural rubber is specifically the \textbf{cis}-isomer. The \textbf{trans}-isomer of polyisoprene is called Gutta-percha, which is non-elastic.

Answer 1

Step 1: Understanding the Concept:
Natural rubber is a linear polymer of isoprene (2-methyl-1,3-butadiene). The isoprene unit is the basic building block (monomer) of the polymer chain.
Step 3: Detailed Explanation:
The IUPAC name for isoprene is 2-methylbuta-1,3-diene.
It consists of a four-carbon chain with double bonds at the first and third positions and a methyl group branching from the second carbon.
Structure:
\[ \begin{array}{c} \text{CH}_3
|
\text{CH}_2 = \text{C} - \text{CH} = \text{CH}_2 \end{array} \]
In natural rubber, these units are linked in a cis-1,4 configuration, which gives rubber its elastic properties.
Step 4: Final Answer:
The structure of the isoprene unit is 2-methyl-1,3-butadiene.