A: `CH_(3)CH=CH_(2)` can undergo cationic polymeisation with greater ease than `CH_(2)=CH_(2)`.
R: `CH_(3)-` groups has +I effect.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark 1.
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark 2.
C. If Assertion is true statement but Reason is false, then mark 3.
D. If both Assertion and Reason are false statements the mark 4.

Answer

To solve the question, we need to analyze the assertion (A) and reason (R) provided:

**Assertion (A):** `CH₃CH=CH₂` can undergo cationic polymerization with greater ease than `CH₂=CH₂`.

**Reason (R):** `CH₃-` groups have +I effect.

### Step-by-Step Solution:

1. **Understanding Cationic Polymerization:**
- Cationic polymerization involves the formation of a carbocation, which is a positively charged carbon species. The stability of this carbocation is crucial for the ease of polymerization.

2. **Analyzing the Structure of the Monomers:**
- The first monomer is propene (`CH₃CH=CH₂`), which has a methyl group (`CH₃`) attached to the carbon of the double bond.
- The second monomer is ethene (`CH₂=CH₂`), which does not have any alkyl groups attached to the double bond.

3. **Carbocation Stability:**
- The stability of a carbocation increases with the number of alkyl groups attached to the positively charged carbon. This is due to the +I (inductive) effect of alkyl groups, which donate electron density to the positively charged carbon, stabilizing it.
- In the case of propene, the carbocation formed after the initial step of cationic polymerization will be a secondary carbocation (due to the presence of one methyl group), which is more stable than the primary carbocation that would form from ethene.

4. **Comparing the Two Monomers:**
- For propene: The carbocation formed is CH₃C⁺H-CH₂, which is stabilized by the +I effect of the methyl group.
- For ethene: The carbocation formed is CH₂C⁺H-CH₂, which is less stable as it has no alkyl groups to stabilize it.

5. **Conclusion:**
- Since the carbocation formed from propene is more stable than that from ethene, propene can undergo cationic polymerization more easily than ethene.

6. **Evaluating the Assertion and Reason:**
- Both the assertion (A) and reason (R) are correct. The reason provided explains why the assertion is true, as the +I effect of the `CH₃` group in propene enhances the stability of the carbocation, facilitating the polymerization process.

### Final Answer:
- **Assertion (A) is true.**
- **Reason (R) is true and is the correct explanation of (A).**

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