How to Master Tricky Chemistry Organic Reaction Mechanisms for Advanced Level

Organic Chemistry represents a massive portion of the Advanced Level Chemistry Paper 2. Many students lose crucial marks because they do not draw reaction mechanism arrows correctly. Let us break down the core mechanisms you must know.

Core Mechanisms Required

1. Electrophilic Addition: The reaction of alkenes with halogens or hydrogen halides (e.g., ethene with HBr). Remember Markovnikov's Rule for asymmetrical alkenes!
2. Nucleophilic Substitution: SN1 and SN2 mechanisms. Know how steric hindrance affects tertiary halogenoalkanes versus primary ones.
3. Electrophilic Substitution: Nitration and halogenation of benzene. Be precise with the formation of the electrophile (NO2+ or Cl+).

Common Mistakes to Avoid

• Wrong Arrow Direction: Arrows must ALWAYS start from a lone pair of electrons or a chemical bond, and point directly to the electron-deficient atom.
• Missing Charges: Do not forget the positive charge on the carbocation intermediate or the negative charge on leaving groups!