Catalytic cracking:
- Converts one large alkane into a smaller alkane and a smaller alkene
- 500oC in the presence of a zeolite catalyst
- Produces higher proportions of branched and cyclic alkenes.
- E.g. C10H22 C3H6 + C7H16
Non-catalytic cracking:
- Higher temperatures in the presence of steam
- Produces a higher proportion of alkenes.
- E.g. C10H22 C3H6 + C7H16
Reforming:
- Increases octane number of a fuel by increasing volatility
- Converts straight-chain alkanes into branched alkanes or cyclic alkanes or
arenes
- Converts cyclic alkanes into arenes
- Hydrogen can be a byproductPlatinum catalyst at 500oC under high pressure
- E.g. heptane methylbenzene + 4 H2
Complete combustion:
- Excess of O2
- Alkanes, alcohols or alkenes react with oxygen
- Produces carbon dioxide and water.
- E.g. CH4 + 2 O2 CO2 + 2 H2O
Incomplete combustion:
- Lack of O2
- Alkanes, alcohols or alkenes react with oxygen
- Produces carbon monoxide or carbon, and water.
- E.g. 2 CH4 (g) + O2 (g) CO (g) + 2 H2O (l)
Fermentation of glucose:
- Starch/sugar in crops is used. They are fermented, converting the starch to
glucose, and then glucose to ethanol and CO2.
- Catalysed by zymase enzyme in yeast.
- C6H12O6 (aq) 2 CO2 (g) + 2 C2H5OH (aq)
Alkanes with halogens
- Free radical substitution
- Produces a range of products due to chain reactions in propagation
- Requires UV light
- Produces halogenoalkanes