Homologous series: A family of compounds that have similar properties and bonding, such as the alkenes or alcohols
Hydrocarbon: A compound containing hydrogen and carbon only
Saturated: Contains only single bonds
Unsaturated: Contains a double bond
General Formula: e.g. CnH2n A formula that fits all the members in a homologous series
Isomerism: Where molecules have the same molecular formula but a different structural or displayed formula.
Alkanes have the general formula of CnH2n+2
|Methane (CH4)||Ethane (C2H6)||Propane (C3H8)||Butane (C4H10)|
Different products come from combustion of hydrocarbons.
CH4 + Br2 → CH3Br + HBr Under UV light, bromine substitutes with hydrogen into methane to produce bromomethane.
Alkenes are another homologous series. They have a general formula of CnH2n.
|Methane (CH4)||Ethane (C2H6)|
A test for alkenes is an addition reaction with bromine water. The bromine water, which starts brown, goes colourless. C2H4 + Br2 → C2H4Br2
Ethanol can be manufactured by passing ethene and steam over phosphoric acid, which acts as a catalyst, at a temperature of around 300˚C and a pressure of around 60-70 atmospheres.
Ethanol can also be manufactured by the fermentation of sugar by yeast, which takes place at a temperature of around 30˚C. C6H12O6 → 2C2H5OH + 2CO2
|Fermentation||Hydration of Ethene|
|Raw Materials||Renewable resources||Non-renewable (crude oil)|
|Rate of reaction||Very slow||Fast|
|Quality||Dilute solution- needs processing||Pure ethanol|
|Conditions||Low temperature + pressure||Very high temperature and pressure – incurs costs|
Ethanol can be dehydrated, by passing it over hot AlO3. This acts as a catalyst to speed up the reaction.
C2H5OH → C2H4 + H2O