In the natural rubber ' Caoutchouc'. The isoprene units are joined by

Options

A. Head-to -head
B. Tail-to-tail
C. Head-to-tail
D. All of these

Explanation

To determine how the isoprene units are joined in natural rubber (Caoutchouc), we can analyze the structure of isoprene and how these units polymerize.

### Step-by-Step Solution:

1. **Understanding Isoprene Structure**:
- Isoprene is a diene with the formula C5H8, which can be represented as CH2=C(CH3)-CH=CH2. It contains two double bonds.

2. **Polymerization of Isoprene**:
- In natural rubber, isoprene units undergo polymerization to form long chains. The polymerization process involves the breaking of double bonds to form single bonds between the isoprene units.

3. **Identifying the Joining Method**:
- The isoprene units can connect in different ways: head-to-head, tail-to-tail, or head-to-tail.
- In the head-to-tail arrangement, the head (the end with the double bond) of one isoprene unit connects to the tail (the end with the single bond) of another isoprene unit.

4. **Analyzing the Connections**:
- When we visualize the connections, we see that one isoprene unit's head (CH2) connects to the tail (CH) of another isoprene unit, forming a continuous chain.
- This arrangement allows for a flexible and elastic structure, characteristic of natural rubber.

5. **Conclusion**:
- Based on the analysis, the isoprene units in natural rubber (Caoutchouc) are primarily joined in a head-to-tail manner.

### Final Answer:
The isoprene units in natural rubber (Caoutchouc) are joined by **head to tail**.

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