Isomerism and aromaticity

This resource should hopefully cover the basic knowledge needed for this topic in the WJEC Chemistry exam. Good luck :)

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What is an enantiomer?
An isomer that is a non-superimposable mirror image.
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Define a racemic mixture?
This is an equimolar mixture of both types of optical isomer.
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What is E - Z isomerism?
This is when you have a double bond which has different functional groups on either side of the carbon atom. Hence you have a diffferent isomer depending on whether like functional groups are on the same side or not.
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What is E isomerism?
Generally the like functional groups will be diagonally opposite each other.
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What is Z isomerism?
Generally the like functional groups will both be on the same side of the double bond.
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What is stereoisomerism?
This is when atoms and groups are arranged differently in space.
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What is an optical isomer?
An optical isomer has to have a chiral centre [when there are four different groups that join onto the carbon atom], they are mirror images of each other and will rotate polarized light either to the right or left.
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Why does a racemic mixture not affect plane polarised light?
This is accuse there is an equimolar mixture, so half will rotate polarized light to the left and half will rotate it to the right, as a result, there will appear to have no effect on the light.
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What is elctrophilic substitution?
The replacement of (ring hydrogen atoms) by an electron deficient group such as NO2+ and CH3+
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Describe the process of nitration of benzene
Benzene is reacted with a mixture of concentrated nitric and sulfuric acids at 50 degrees or below. If the temperature rises above this then 1,3-dinitrobenzene can be formed, which is a pale yellow solid.
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Describe the process of halogenation of benzene
The halogen and benzene is reacted in the presence of a suitable catalyst [such as Iron (III) bromide for bromine substitution]. The catalyst is often described as a halogen a carrier. The reaction is done out of direct sunlight. [electrophilic sub.]
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The alkylation of benzene (friedel-crafts)
A catalyst of aluminium chloride is often used, and the alky group is given using a suitable chemical, for example chloromethane. Once again this is an electrophilic substitution.
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What is the "bond energy"?
`This is the energy needed to break a covalent bond. The higher the value the stronger the bond.
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Can phenol be made from chlorobenzene?
Yes but the conditions needed are extreme as it is already very stable due to the integration of electrons into the stable pi ring system. NaOH at 300 degrees under extreme pressure is required.
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Other cards in this set

Card 2

Front

Define a racemic mixture?

Back

This is an equimolar mixture of both types of optical isomer.

Card 3

Front

What is E - Z isomerism?

Back

Preview of the front of card 3

Card 4

Front

What is E isomerism?

Back

Preview of the front of card 4

Card 5

Front

What is Z isomerism?

Back

Preview of the front of card 5
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