1. Organic Chemistry Revision

2. Crude Oil
What is it?
How is it formed?
Where is it found?

3. Fractional Distillation – making crude oil useful
Crude oil is heated to make it vaporise
Vapour goes into the fractioning column
The vapour is cooled
Different fractions of the oil condense and are collected at different temperatures
As the length of the hydrocarbon chain increases, the boiling point and viscosity also increase. Flammability and volatility decrease.

5. Alkanes Alkanes are a homologous series.
Members of a homologous series have similar properties and can be represented by a general formula
For alkanes, the formula is CnH2n+2

7. Properties of alkanes
The first four (methane – butane) are gases at RTP
As the number of carbon atoms increases, the melting points, boiling points and densities increase
5-17 C atoms = liquids
18+ C atoms = solids
C-C bonds and C-H bonds are very strong, so alkanes are not very reactive
But – will combust. Very exothermic!

8. Complete and incomplete combustion
Hydrocarbon + oxygen  carbon dioxide + water
Happens when there is plenty of air.
Incomplete:
Hydrocarbon + oxygen  carbon monoxide + carbon + water
Happens when air is restricted

9. Alkenes Alkanes are a homologous series.
For alkenes, the general formula is CnH2n

10. Properties of alkenes Have a carbon-carbon double bond
As the number of carbon atoms increases, the melting points, boiling points and densities increase
Combust like alkanes but burn with sootier flames due to their higher carbon : hydrogen ratio
More reactive than alkanes – why?
Unsaturated

11. Cracking Why? – Supply and demand Process = thermal decomposition
Products = alkane + alkene(s)
Conditions needed: heat ( degrees), catalyst (mixture of silicon dioxide and aluminium oxide)

12. Addition Polymerisation
What is a polymer?
Addition reaction = 2 or more molecules join together to give a single product
Example ethene  poly(ethene) or polythene
Conditions:
200 degrees C
2000atm

13. Condensation Polymerisation
Example = nylon
Similar to addition, but the formation of a condensation polymer is accompanied by the release of an additional small molecule (such as?)
Nylon monomers are di-amines and di-carboxylic acids:

14. Manufacture of ethanol
By the reaction of steam and ethene:
Conditions:
High temp (300 degrees C)
Catalyst = phosphoric acid
60 atm

15. Advantages and disadvantages
Fast and efficient
Continuous
Product is relatively pure
Some countries may have local oil supply
But – crude oil is non-renewable

16. Manufacture of ethanol
By the fermentation of sugars:
Glucose  ethanol + carbon dioxide
Conditions:
ENZYME
Slightly above room temperature
The carbon dioxide is allowed to escape and air prevented from getting in, to stop the oxidisation of the alcohol.

17. Advantages and disadvantages
Cheap
Renewable resource (sugar cane)
Cheap labour in the countries where sugar cane is grown
But –
Reaction is slow
Inefficient batch process
Poor quality product
Alcohol must be distilled from the fermentation mixture (costly)

18. Dehydration of ethanol to ethene
Done by passing alcohol vapour over an aluminium oxide catalyst
Ethanol  ethene + water
Catalyst = aluminium oxide