Study Notes
Organic chemistry involves the study of carbon-containing compounds and their reactions. Key areas include types of organic reactions, synthetic routes, and stereoisomerism.
- Nucleophilic Substitution Reactions — involve the replacement of a halogen atom in a halogenoalkane by a nucleophile. Example: Hydroxide ions replacing bromine in bromoethane to form ethanol.
- SN1 Mechanism — a two-step nucleophilic substitution reaction where the rate depends on the concentration of the halogenoalkane. Example: Substitution of 2-bromo-2-methylpropane by hydroxide ions.
- SN2 Mechanism — a one-step nucleophilic substitution reaction where the rate depends on both the halogenoalkane and nucleophile. Example: Substitution of bromoethane by hydroxide ions.
- Electrophilic Addition — involves the addition of an electrophile to an alkene double bond. Example: Addition of hydrogen bromide to ethene.
- Stereoisomerism — involves isomers with the same molecular formula but different spatial arrangements. Example: Cis/trans isomers in alkenes.
- Optical Isomers — are non-superimposable mirror images due to chiral centers. Example: Enantiomers of carvone with different smells.
- Racemic Mixtures — contain equal amounts of enantiomers and are optically inactive. Example: Racemic mixture of ibuprofen.
Exam Tips
Key Definitions to Remember
- Nucleophilic substitution
- SN1 and SN2 mechanisms
- Electrophilic addition
- Stereoisomerism
- Optical isomers
Common Confusions
- Difference between SN1 and SN2 mechanisms
- Cis/trans vs E/Z isomerism
- Optical activity and racemic mixtures
Typical Exam Questions
- What is the difference between SN1 and SN2 mechanisms? SN1 is a two-step reaction dependent on halogenoalkane concentration, while SN2 is a one-step reaction dependent on both halogenoalkane and nucleophile.
- How does electrophilic addition occur in alkenes? Electrophiles attack the electron-rich C=C bond, forming a carbocation intermediate.
- What are optical isomers? Non-superimposable mirror images due to chiral centers.
What Examiners Usually Test
- Understanding of reaction mechanisms
- Ability to identify and explain types of isomerism
- Application of Markovnikov’s rule in electrophilic addition