Question

Write a mechanism for the polymerization of methyl vinyl ether initiated by 2-chloro2-phenylpropane and \(\mathrm{SnCl}_{4}\). Label the initiation, propagation, and termination steps.

Short answer

Question: Outline the step-by-step mechanism for the polymerization of methyl vinyl ether initiated by 2-chloro-2-phenylpropane and \(\mathrm{SnCl}_{4}\). Answer: The mechanism for the polymerization of methyl vinyl ether initiated by 2-chloro-2-phenylpropane and \(\mathrm{SnCl}_{4}\) consists of three main steps: initiation, propagation, and termination. In initiation, the carbocation is formed by reacting the initiator with the catalyst, which then reacts with the monomer to create a new carbocation. In propagation, this new carbocation reacts with another monomer to grow the polymer chain. Termination involves the end of the polymerization process, either through the reaction of the propagating carbocation with a counterion or between two carbocations to form a stable product.

Step-by-step solution

Initiation

The initiation step begins with the reaction between the initiator, 2-chloro-2-phenylpropane, and the catalyst, \(\mathrm{SnCl}_{4}\). This leads to the formation of a carbocation and a \(\mathrm{SnCl}_{3}^{-}\) ion. The carbocation will then react with the methyl vinyl ether monomer to form a new reactive species (another carbocation) that will be involved in the propagation. The initiation step can be outlined as follows: 1. 2-chloro-2-phenylpropane + \(\mathrm{SnCl}_{4}\) → carbocation + \(\mathrm{SnCl}_{3}^{-}\) 2. Carbocation + methyl vinyl ether → new carbocation

Propagation

The propagation step involves the reaction of the carbocation formed in the initiation step with another methyl vinyl ether monomer. This will create a longer chain with an unsaturated carbon and will generate a new carbocation that can continue reacting with more monomers. This step is repeated multiple times, leading to the growth of the polymer chain. The propagation step can be represented as: 1. New carbocation + methyl vinyl ether → longer chain carbocation 2. Repeat step with more monomers to grow the polymer chain

Termination

The termination step involves the end of the polymerization process. This can occur through various mechanisms, such as the reaction between the propagating carbocation and a counterion (e.g., \(\mathrm{SnCl}_{3}^{-}\)) or between two carbocations to form a stable product. The termination step can be illustrated as follows: 1. Longer chain carbocation + counterion (e.g., \(\mathrm{SnCl}_{3}^{-}\)) → end of polymerization process (stable polymer product) 2. Longer chain carbocation A + longer chain carbocation B → end of polymerization process (stable polymer product) By illustrating the initiation, propagation, and termination steps, we have described the mechanism of the polymerization of methyl vinyl ether initiated by 2-chloro2-phenylpropane and \(\mathrm{SnCl}_{4}\).