Key Organic Reactions
Combustion
All organic compounds burn in O₂.
Complete: → CO₂ + H₂O
Incomplete: → CO
or C + H₂O
Addition
Across a C=C double bond. Only one product.
e.g. Ethene + Br₂ →
1,2-dibromoethane
Test: decolourises bromine water
Substitution
One atom/group replaces another. Typical for alkanes.
e.g. CH₄ + Cl₂ → CH₃Cl + HCl (UV light)
Condensation
Two molecules join with loss of water.
e.g. Alcohol + carboxylic acid → ester +
H₂O
(esterification)
Oxidation of Alcohols
Using acidified K₂Cr₂O₇ (orange → green when reduction occurs):
- Primary alcohol → aldehyde (distil) → carboxylic acid (reflux)
- Secondary alcohol → ketone
- Tertiary alcohol → No oxidation (resistant)
Think About It
How can you distinguish between an alkane and an alkene using a simple test?
Add bromine water (orange/brown). Alkenes decolourise it (addition reaction across C=C). Alkanes do NOT react with bromine water at room temperature — no colour change.