What is the general mechanism of free radical halogenation?

1 Answer
Jun 10, 2015

Free radical halogenation involves initiation, propagation, and termination steps.

Explanation:

Consider the free radical chlorination of methane.

Step 1. Initiation

The initiation step involves the homolytic cleavage of a #"Cl-Cl"# bond to form two #"Cl"# atoms.

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Step 2. Propagation

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  • A #"C"# atom removes an #"H"# from methane, producing #"HCl"# and a methyl radical.

  • The newly-formed methyl radical abstracts a #"Cl"# from a chlorine molecule, producing chloromethane and re-forming a #"Cl"# atom.

Step 3. Termination

In the termination steps, the radicals combine in all possible combinations.

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The termination products are chlorine, chloromethane, and ethane.