Addition polymers are those in which monomers are converting into polymer by addltlon reaction. This addition reaction follow Radical mechanism in which firstly radical form than this propagate a chain than this chain terminate to form polymer
Which of the following is a propagation rejection?

Options

A. `dotR+CH_(2)=CH_(2)toR-CH_(2)-dotCH_(2)`
B. `RCH_(2)CH_(2)+CH_(2)=CH_(2)toR-CH_(2)-CH_(2)-CH_(2)-dotCH_(2)`
C. `(RCH_(2)CH_(2)CH_(2)dotCH_(2))_(n)toR(CH_(2)CH_(2))_(2n)R`
D. None of these

Answer

To solve the question regarding which of the given reactions is a propagation rejection in the context of addition polymers formed through radical mechanisms, we can follow these steps:

### Step-by-Step Solution

1. **Understand the Mechanism of Addition Polymers**:
- Addition polymers are formed through a radical mechanism involving three main steps: initiation, propagation, and termination.
- In the initiation step, free radicals are generated.
- The propagation step involves the reaction of these free radicals with monomers, leading to the growth of the polymer chain.
- The termination step occurs when the growing polymer chain stops growing, resulting in the final polymer product.

2. **Identify the Propagation Reaction**:
- A propagation reaction involves the addition of a free radical to a monomer, resulting in a new radical that can continue to react with more monomers.
- The key characteristic of a propagation reaction is the presence of a free radical that continues the chain reaction.

3. **Evaluate the Given Options**:
- We need to analyze each of the provided reactions to determine if they involve a free radical and if they represent a propagation step.
- Look for reactions that do not involve the formation of a new radical or where the radical does not continue to react with additional monomers.

4. **Determine the Correct Answer**:
- After evaluating the reactions, identify which reaction does not fit the criteria of a propagation reaction. This will be the propagation rejection.
- In the provided options, the second reaction is identified as the one that does not involve a free radical in the propagation step, making it the correct answer.

5. **Conclude**:
- The correct option for the propagation rejection is the second reaction, as it does not involve the continuation of a radical chain.

### Final Answer
The propagation rejection reaction is the second option.