Commercial reactions of alkenes

Crude oil is a mixture of hydrocarbons of varying chain lengths.
- Short hydrocarbons are more useful and in higher demand than longer chains.
- Long chains can be broken down into shorter ones via cracking.

Cracking is a common process in the petrochemical industry.
- Two main types of cracking: Catalytic Cracking and Thermal Cracking.

Carried out at:
- High temperature: around 500 degrees Celsius.
- Slight pressure: usually at atmospheric pressure.
Uses a zeolite catalyst, which is a large solid lattice made of:
- Aluminum, silicon, and oxygen.
Yields hydrocarbons with:
- 5 to 10 carbons.
- Predominantly branched isomers.
Advantages:
- Lower boiling points make branched isomers preferable as fuels.
- Very common for producing petrol.

Carried out at:
- Higher temperature: around 700 degrees Celsius.
- Higher pressure than catalytic cracking.
Yields:
- A larger number of alkenes and shorter hydrocarbon chains (usually less than 5 carbons).
Applications:
- Excellent for polymerization due to presence of alkenes.

Alkanes serve as effective fuels, especially the shorter chains.
Complete Combustion:
- Occurs in the presence of plentiful oxygen.
- Produces carbon dioxide (CO₂) and water (H₂O).
- Example: Complete combustion of octane (C₈H₁₈):
  - Balanced equation:
    C₈H₁₈ + 12.5 O₂ → 8 CO₂ + 9 H₂O
Incomplete Combustion:
- Occurs when oxygen supply is limited.
- Produces carbon monoxide (CO) and water.
- Example: Incomplete combustion of hexane (C₆H₁₄):
  - Balanced equation:
    C₆H₁₄ + 6.5 O₂ → 6 CO + 7 H₂O
Concerns:
- Incomplete combustion is dangerous as it produces toxic carbon monoxide.
- Carbon monoxide is a poisonous gas and reduces overall energy output during combustion.