Free radical polymerisation requires a free radical initior.The most commonly used free radical initiator is:

Options

A. `Ph-CO-O-O-COPh` , benzoylperoxide
B. `(CH_(3))_(3)C-O-O-C(CH_(3))_(3)` , tert-butyl peroxide
C. `C_(6)H_(5)-underset(C_(6)H_(5)-N)underset(||)NrarrO` , azoxybenezene
D. `CH_(2)N_(2)` , diazomethane

Answer

**Step-by-Step Text Solution:**

1. **Understanding Free Radical Polymerization**: Free radical polymerization is a process that involves the use of free radicals to initiate the polymerization of monomers. These free radicals are highly reactive species that can start the chain reaction necessary for polymer formation.

2. **Role of Initiators**: In free radical polymerization, an initiator is required to generate free radicals. The choice of initiator is crucial for the success of the polymerization process.

3. **Factors Influencing the Choice of Initiator**: The selection of a suitable free radical initiator depends on two main factors:
- **Solubility**: The initiator must be soluble in the solvent used for the polymerization. If it is not soluble, it will not effectively initiate the polymerization reaction.
- **Decomposition Temperature**: The decomposition temperature of the initiator must be at or below the boiling point of the solvent. This ensures that the initiator decomposes to form free radicals at the right temperature during the polymerization process.

4. **Commonly Used Initiator**: Among various initiators, **benzoyl peroxide** is the most commonly used free radical initiator. It meets both the solubility and decomposition temperature requirements for many organic solvents.

5. **Structure of Benzoyl Peroxide**: The chemical structure of benzoyl peroxide can be represented as:
- \( \text{Ph-C(=O)-O-O-C(=O)-Ph} \)
- Upon heating, benzoyl peroxide decomposes to produce free radicals, specifically two benzoyloxy radicals, which can initiate the polymerization process.

6. **Conclusion**: Therefore, the most commonly used free radical initiator in free radical polymerization is **benzoyl peroxide**.

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