Question

Write a mechanism for the polymerization of methyl vinyl ether initiated by 2-chloro-2-phenylpropane and \(\mathrm{SnCl}_{4}\). Label the initiation, propagation, and termination steps.

Short answer

Question: Describe the polymerization mechanism of methyl vinyl ether initiated by 2-chloro-2-phenylpropane and \(\mathrm{SnCl}_{4}\) in three main steps: initiation, propagation, and termination.

Step-by-step solution

1. Initiation step

In the initiation step, the 2-chloro-2-phenylpropane reacts with \(\mathrm{SnCl}_{4}\) to form a carbocation intermediate. This reaction can be represented as: \(2\mathrm{-chloro-2-phenylpropane}\) + \(\mathrm{SnCl}_{4}\) \(\rightarrow\) carbocation \(\mathrm{C^{+}}\) + \(\mathrm{SnCl_{3}^{-}}\) + \(\mathrm{2HCl}\) Now, the carbocation intermediate reacts with the methyl vinyl ether monomer to start the polymerization process. carbocation \(\mathrm{C^{+}}\) + methyl vinyl ether \(\rightarrow\) propagating carbocation intermediate

2. Propagation step

In the propagation step, the propagating carbocation reacts with another methyl vinyl ether monomer to add onto the growing polymer chain. This step continues to occur until the termination step takes place. Propagating carbocation intermediate + methyl vinyl ether \(\rightarrow\) extended propagating carbocation intermediate

3. Termination step

Termination can occur in more than one way. In this example, the termination step occurs when two reacting propagating carbocations from the growing polymer chains react with each other to form a bond and close the polymerization process. This is called the "coupling termination" and can be written as: Propagating carbocation intermediate + Propagating carbocation intermediate \(\rightarrow\) Coupled polymer chain Now the entire mechanism for the polymerization of methyl vinyl ether initiated by 2-chloro-2-phenylpropane and \(\mathrm{SnCl}_{4}\) has been described in three steps: initiation, propagation, and termination.