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Isomerism in Alkanes and Alkenes
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What are Isomers?
Different compounds
Same molecular formula
Different structural formula
Different boiling points
The phenomenon is known as
isomerism
What happens to the number of isomers as the number of carbon atoms increase?
The number of isomers
increase
as the number of carbon atoms in a molecule increase
Importance of Isomers
Isomerism is important in petrol fuel for motorcars.
The
petrol fraction
from the fractional distillation of petroleum
contains a lot of straight-chain alkane molecules,
such as octane
.
Car engines don't run smoothly when burning straight-chain molecules
The engines run much better when burning branched-chain isomers
Branched-chain isomers are more expensive.
A cheaper alternatice was to add lead compounds
But lead from car exhausts pollute the air as lead is a poisonous metal
Due to pollution controls, lead is no longer used and so petrol is now more relatively expensive as they contain branched-chain alkanes.
Manufacture of Margarine
Some foods are described as being polyunsaturated
This means their organic molecues contain C=C bonds
Vegetable oils are polyunsaturated
These polyunsaturated oils are considered to be healthier to eat than saturated oils
Margarine is made by reacting vegetable oil with Hydrogen in the presence of a nickel catalyst
Not all C=C bonds in the vegetable oil react with hydrogen.
The margarine is said to be partially hydrogenated.
The more hydrogenated the margarine, the fewer C=C bonds it has and the harder it is.
The Ripening of Fruits
Unripe fruits produces small amounts of ethene, which hep it to ripen
Author
zyanhs
ID
167644
Card Set
Isomerism in Alkanes and Alkenes
Description
Description of Isomers
Updated
2012-08-27T11:55:18Z
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