Silicon has a strong tendency to form polymers like silicones. The chain length of silicone polymer can be controlled by adding

Options

A. `MeSiCl_(3)`
B. `Me_(2)SiCl_(2)`
C. `Me_(3)SiCl`
D. `Me_(4)Si`

Explanation

To solve the question regarding how the chain length of silicone polymers can be controlled, we can break down the solution into the following steps:

### Step 1: Understanding Silicone Polymers
Silicone polymers are long chains made up of silicon atoms, often alternating with oxygen atoms. They can also have organic groups attached to them, such as methyl (CH3) groups. The structure of silicone can be represented as:
\[ \text{(R}_2\text{SiO)}_n \]
where R represents the organic groups.

**Hint:** Recall that silicone polymers consist of repeating units of silicon and oxygen, which can form long chains.

### Step 2: Chain Growth and Termination
The growth of silicone chains occurs through the reaction of silanol groups (Si-OH) that can further react with each other, leading to longer chains. However, to control the length of these chains, we need to terminate the polymerization process.

**Hint:** Think about what chemical groups can stop the chain from growing further.

### Step 3: Identifying the Termination Agent
To terminate the chain, we can add a compound that will react with the silanol groups but will not allow further polymerization. One effective compound for this purpose is trimethylsilyl chloride (Me3SiCl). When added, it reacts with the silanol groups to form trimethylsilyl (Me3Si) groups, which do not have the ability to further react and form chains.

**Hint:** Consider the structure of Me3SiCl and how it can interact with the silanol groups.

### Step 4: Reaction Mechanism
When Me3SiCl is added to the silicone polymer, it reacts with the Si-OH groups:
\[ \text{Si-OH} + \text{Me}_3\text{SiCl} \rightarrow \text{Si-O-SiMe}_3 + \text{HCl} \]
This reaction effectively terminates the chain by replacing the hydroxyl groups with trimethylsilyl groups, preventing further polymerization.

**Hint:** Visualize the reaction to see how the hydroxyl groups are replaced, leading to chain termination.

### Step 5: Conclusion
By adding trimethylsilyl chloride (Me3SiCl), we can effectively control the length of silicone polymers by terminating the polymerization process. Thus, the correct answer to the question is:
**Me3SiCl**.

**Final Answer:** The chain length of silicone polymer can be controlled by adding **Me3SiCl**.