Homogolous Series - same general formula, similar chemical reactions e.g. alkane/ alkene
Saturated - all single bonds
Unsaturated - contain a carbon-carbon double bond
Isomerism - same molecular formula, different displayed formula
- Dissolve sugar or starch in water and add yeast
- Leave the mixture to ferment at 25-40C for several days in the absence of air
- Filter off excess yeast for a dilute soluion of ethanol
When the ethanol content rises above 15%, the yeast is killed. The enzymes in the yeast produce glucose. The glucose is then converted into ethanol.
C6H12O6(aq) --> 2C2H5OH(aq) + 2CO2(g)
2. Direct hydration of ethene
- Ethene+steam is passed over a phosphoric acid catalyst at 300C and 60-70 atm
C2H4(g) + H2O(g) --> C2H5OH(g)
The ethanol is then condensed as a liquid. The ethene used is obtained from crude oil.
Renewable sources (sugar cane) Non-renewable sources (crude oil)
Batch process Continuous
Dilute ethanol Pure ethanol
Low temps High temp & pressure
REACTIONS OF ETHANOL
Combustion: C2H5OH(l) + 3O2(g) --> 2CO2(g) + 3H20(l)
Dehydration: passing ethanol vapour over hot aluminium oxide.