CHEM 125b - Lecture 3 - Rate and Selectivity in Radical-Chain Reactions

Lecture 3 - Rate and Selectivity in Radical-Chain Reactions


The reactivity-selectivity principle explains why bromine atoms are more selective that chlorine atoms in abstracting hydrogen atoms from carbon. A free-radical mechanism for adding HBr to alkenes explains its anti-Markovnikov regiospecificity. Careful analysis is required to understand kinetic order for reactions involving catalysts. Termination of radical-chain reactions can make their rate half-order in the initiator. Selectivity due to protonation of radicals and their reaction partners illustrates the importance of ionic charge in determining reaction rates.


Professor McBride's website resource for CHEM 125b (Spring 2011)

This website may include third-party materials pertaining to relevant topics, provided for the user's convenience. Yale does not control or take responsibility for the content of any off-site pages or linked sites.

Course Media





Low Bandwidth Video

mov [100MB]

High Bandwidth Video

mov [500MB]