In a radical polymerisation the shift in having the radical at the end of the growing chain to somewhere else along the chain during the reaction is

🔬 What Happens in Radical Polymerization?

In radical polymerization, the growing polymer chain typically has a radical at its terminal end. However, under certain conditions, this radical can shift to a different position on the same chain — typically moving internally.

💡 What Is This Shift Called?

• Initiation: The beginning of polymerization — not related to radical migration.
• Termination: Ends the polymer chain growth — may involve combination or disproportionation, but not radical shifting.
• Disproportionation: A type of termination involving transfer of hydrogen — does not describe internal radical migration.
• Back biting: This is the correct term! It refers to the intramolecular transfer of the radical from the chain end to an internal carbon atom along the chain. This leads to the formation of cyclic structures or branched chains.

✔️ Final Answer:

Back biting