Free Radical Halogenation Module: Part 2: Regioselectivity: Determining the Major Product

Posted on September 8th, 2013

This is the second part of a multi-part module on Free Radical Halogenation.

View the first part here: Part 1: The Mechanism


Radical bromination will always replace the C-H bond on the MOST subsituted carbon center because the stability of the radical intermediate is higher with increasing substituents on the carbon center.

Free Radical Halogenation Module Pic 5

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This selectivity is the same, but a weaker consideration, for radical chlorination which obeys Hammond’s Postulate in that stability of the radical center is outweighed by the extreme exothermicity of radical chlorination (compared to bromination), thus a mixture of chlorinated products is observed.


There are multiple examples of this reaction to review in the Study Mode. When ready, test your knowledge in the Quiz Mode.

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Check out Part 3: Stereoslectivity – Determining stereochemistry of carbon centers