# Organic Chemistry (IB)
IB Organic Chemistry covers nomenclature, functional groups, types of reactions, and at HL, reaction mechanisms (SN1, SN2, electrophilic addition) and stereoisomerism.
1. Homologous Series and Functional Groups
| Series | Functional Group | General Formula | Suffix |
|---|---|---|---|
| Alkanes | C−C single bonds | -ane | |
| Alkenes | C=C double bond | -ene | |
| Alcohols | −OH | -ol | |
| Aldehydes | −CHO | — | -al |
| Ketones | −CO− | — | -one |
| Carboxylic acids | −COOH | — | -oic acid |
| Esters | −COO− | — | -oate |
| Amines | −NH₂ | — | -amine |
| Halogenoalkanes | −X (Cl, Br, I) | — | prefix: chloro-, bromo- |
2. Types of Reactions
| Type | Description | Example |
|---|---|---|
| Combustion | Burning in O₂ | CH₄ + 2O₂ → CO₂ + 2H₂O |
| Substitution | One atom/group replaces another | CH₃Br + NaOH → CH₃OH + NaBr |
| Addition | Atoms add across C=C | C₂H₄ + HBr → C₂H₅Br |
| Elimination | Small molecule lost, C=C formed | C₂H₅OH → C₂H₄ + H₂O |
| Condensation | Two molecules join, losing H₂O | Acid + alcohol → ester + H₂O |
| Oxidation | Gain O or lose H | Primary alcohol → aldehyde |
| Reduction | Lose O or gain H | Aldehyde → primary alcohol |
3. Key Reactions
Alkenes: electrophilic addition (HBr, Br₂, H₂O), polymerisation Alcohols: oxidation (1° → aldehyde → acid; 2° → ketone), dehydration, esterification Halogenoalkanes: nucleophilic substitution (NaOH, KCN, NH₃), elimination
4. Mechanisms (HL)
SN1 (Tertiary)
- C−X breaks heterolytically → carbocation + X⁻
- Nucleophile attacks carbocation Rate = k[RX]
SN2 (Primary)
- Nucleophile attacks C simultaneously as X leaves Rate = k[RX][Nu⁻]
Electrophilic Addition (Alkenes)
- Electrophile attracted to C=C π bond
- Carbocation intermediate forms
- Nucleophile attacks carbocation
5. Stereoisomerism
E/Z (geometric) isomerism: restricted rotation around C=C; different groups on each C
Optical isomerism: chiral centre (4 different groups on C); enantiomers are non-superimposable mirror images; rotate plane-polarised light in opposite directions
6. Practice Questions
- Name and draw the structural formula of 2-methylpropan-1-ol.
- Write equations for the oxidation of butan-1-ol to (a) butanal and (b) butanoic acid.
- Draw the mechanism for electrophilic addition of HBr to propene.
- Identify the chiral centre in 2-bromobutane.
- What type of reaction occurs between ethanoic acid and methanol? Write the equation.
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Summary
- Functional groups determine chemical properties
- Key reactions: addition, substitution, elimination, condensation, oxidation
- HL mechanisms: SN1, SN2, electrophilic addition
- Stereoisomerism: E/Z (geometric) and optical (chiral centre)