1. 29. Organic Chemistry Revision 3 (Reaction Mechanism)1. Recap on Free Radical Substitution Note: Half arrows showing homolytic fission for initiation step, propagation step to create chain reaction and termination step where a bigger alkane can be formed. 2. Use of Probability and Stability of Radical Approaches to predict ratio and explain major products. 3. Recap on Electrophilic Addition Note: Full arrow from nucleophilic alkene to electrophile to generate carbocation (most stable). 4. Different products may be formed from second step of EA depending on the nucleophiles present in the second step. Major product is formed from the nucleophile with the highest concentration. 5. Recap on Electrophilic Substitution Note: A catalyst is used to generate a stronger electrophile. Full arrow from the nucleophilic benzene ring to the electrophile to generate the arenium ion based on the directing effect of the existing group (if any).