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 (cis-1,4-polyisoprene). Isoprene is the fundamental monomer unit.
Step 2: Detailed Explanation:
The isoprene molecule consists of a four-carbon chain with two double bonds (a conjugated diene) and a methyl group as a substituent.
IUPAC Name: 2-Methyl-1,3-butadiene.
Structure:
\[ \begin{array}{c} \text{CH}_2 = \text{C} - \text{CH} = \text{CH}_2
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\text{CH}_3 \end{array} \]
When it polymerizes, the double bonds shift to the center to form the polymer chain.
Step 3: Final Answer:
The chemical structure of the isoprene unit is \( CH_2=C(CH_3)-CH=CH_2 \).