**Correct Option: B. Free radical polymerization** ### Detailed Explanation: **What are Addition Polymers?** Addition polymers are large molecules formed by the repeated addition of monomer units that contain a double bond (typically carbon-carbon double bonds, C=C). The process of forming these polymers involves breaking the double bonds in the monomers, allowing them to link together into long chains. **Why is Free Radical Polymerization the Correct Answer?** Free radical polymerization is a common method for synthesizing addition polymers. Here’s how it works: 1. **Initiation**: The process begins with the generation of free radicals, which are highly reactive species with unpaired electrons. This can be achieved using initiators such as peroxides or azo compounds that decompose upon heating or exposure to light, producing free radicals. 2. **Propagation**: The free radicals react with the double bonds of the monomers, creating a new radical at the end of the growing polymer chain. This new radical can then react with another monomer, continuing the chain growth. This step can repeat many times, leading to the formation of long polymer chains. 3. **Termination**: The polymerization process can terminate in several ways, such as when two free radicals combine to form a stable bond, or when a radical reacts with an inhibitor that stops the chain growth. **Example**: A common example of free radical polymerization is the polymerization of ethylene (C2H4) to form polyethylene, a widely used plastic. ### Why the Other Options are Incorrect: **A. Condensation Polymerization**: - Condensation polymerization involves the reaction of monomers with functional groups (like -OH, -COOH, -NH2) that leads to the elimination of small molecules (like water or methanol) as byproducts. This method is not used for addition polymers, which do not involve the loss of small molecules. Instead, condensation polymers are typically formed from monomers that contain two or more different functional groups. **C. Hydrolysis**: - Hydrolysis is a chemical reaction involving the breaking of bonds in a molecule by the addition of water. It is not a method for synthesizing addition polymers. Instead, hydrolysis is often involved in the breakdown of polymers or in the formation of monomers from larger molecules. **D. Electrophilic Substitution**: - Electrophilic substitution is a reaction mechanism typically associated with aromatic compounds, where an electrophile replaces a hydrogen atom on the aromatic ring. This process does not lead to the formation of addition polymers and is not relevant to the synthesis of polymers from alkenes. ### Summary of Key Points: - **Addition polymers** are formed from monomers with double bonds through a process that does not involve the loss of small molecules. - **Free radical polymerization** is the primary method for synthesizing addition polymers, involving initiation, propagation, and termination steps. - **Condensation polymerization**, **hydrolysis**, and **electrophilic substitution** are not suitable methods for synthesizing addition polymers. ### Revision Summary: - Addition polymers are formed from monomers with double bonds. - Free radical polymerization is the main method for synthesizing these polymers. - Other methods like condensation polymerization, hydrolysis, and electrophilic substitution do not apply to addition polymers. - Understanding the mechanisms of polymerization is crucial for grasping polymer chemistry.