Reactions of Arenes

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  • Created by: J.E.C.
  • Created on: 30-04-14 10:11
Describe the arrangement of the six electrons in the delocalied system of benzene?
Electrons do not belong to a particular carbon so are free to move around the ring. They spread out in a cloud which extends above and below the plane of the benzene ring.
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Benzene reacts with electrophiles because it tends to...?
Attract positive ions or atoms with partial positive charges within molecules.
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Although alkenes react with electrophiles in ___ reaction, benzene undergoes ___ with electrophiles? By reacting in this way the stable benzene ring is...?
Addition, substitution. Kept intact
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Describe the first step of bromination of benzene?
The benzene ring reacts with the electrophile Br+. (Electrophilic substitution)
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What are the reagents and conditions for bromination of benzene? What happens to the bromine and what else is given off?
FeBr3 catalyst. Bromine decolourises. Fumes of H-Br given off.
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The bromine molecule become ___ as it approaches the benzene ring, the ___ charged end acts as the elctrophile? Iron filings help speed up this reaction by...?
Polarised, Positively. Polarising the bromine molecule even more.
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It is thought the FeBr3 helps polarise the bromien by...? This means the FeBr3 becomes...?
Accepting a lone pair. FeBr4-
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The Br+ then...?
attaches to one of the Carbons on the benzene ring meaning a H+ is lost.
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The H+ reacts with the ___ to regenerate the...?
FeBr4-, the FeBr3 catalyst.
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What is the nitrating mixture for nitrating benzene? For this reaction the temperature must be...?
Mixture of concentrated nitric acid and concentrated sulfuric acid. Below 55 degrees celcius.
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The product of nitration of benzene are...?
Nitrobenzene and H2O.
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At higher temperature, nitration of bezene would result in...?
di- and tri- substituted compounds.
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What is the electrophile involved in nitration of benzene and how is it formed?
NO2+. HNO3 + 2H2SO4 --> NO2+ and 2HSO4- and H3O+
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How would you form benzenesulfonic acid?
Heat benzene and concentrated sulfuric acid under reflux for several hours.
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The elctrophile in sulfonation is ___, therefore the other product of the reaction must be...?
SO3, H2O
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The __ atom in SO3 is the elctrophile and it is this atom that attaches to the benzene ring?
Sulfur
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What bonding would surround the sulfur atom that is attached to the benzene?
2 double bonds to O atoms, 1 single bond to the C atom of the benzene ring, 1 single bond to OH
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Benzenesulfonic acid is a strong acid and forms salts in __ solutions? Most detergents contain this type of salt, which part attaches to fats and which part to water?
Alkaline. Hydrocarbon part > fats. Ionic part > water
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What are the reagents and conditions for Chloroination of benzene?
Reagents: benzene, Cl2, AlCl3 catalyst. Room temperature, anhydrous conditions.
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Describe the mechanism for chlorination of benzene?
Aluminium Chloride polarises Cl2 to produce Cl+ electrophile. The Cl+ attaches to one of the carbon's on the benzene and one of the Cl atoms from AlCl4- attaches to the H+ lost from the benzene. Therefore AlCl3 is reformed.
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What is a Friedel-Crafts reaction - give example?
Aluminium Chloride is used as a catalyst to help polarise halogen-containing organic molecules and cause them to substitute in a benzene ring.
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What conditions and reagents would be required when benzene is warmed with chloromethane?
Benzene, CH3-Cl, AlCl3 and reflux
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The positively charged C atom of the chloromethane reacts with the benzene ring to form ___ which is an ___ reaction?
Methylbenzene, alkylation
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How does an acylation reaction of benzene take place?
The chlorine is lost from the acyl chloride and the remainder of the reagent attaches to the benzene ring and H-Cl is given off.
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Friedel-crafts reactions provide a way of adding...?
Carbon atoms to the benzene ring or build up side chains.
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Friedel-crafts reactions have been used to create 'ionic liquids' which are promoted as new 'green' alternatives because...? (4)
1. Low volatility reduces emissions 2. Low flammability and toxicity increases safety 3.Require lower temperatures for their reactions to take place 4. Can be easily recycled
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How would you introduce an R group onto a benzene molecule?
React with RCl and AICl3, reflux, anhydrous
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How would you introduce SO2OH onto benzene?
React with H2SO4 under reflux.
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Other cards in this set

Card 2

Front

Benzene reacts with electrophiles because it tends to...?

Back

Attract positive ions or atoms with partial positive charges within molecules.

Card 3

Front

Although alkenes react with electrophiles in ___ reaction, benzene undergoes ___ with electrophiles? By reacting in this way the stable benzene ring is...?

Back

Preview of the front of card 3

Card 4

Front

Describe the first step of bromination of benzene?

Back

Preview of the front of card 4

Card 5

Front

What are the reagents and conditions for bromination of benzene? What happens to the bromine and what else is given off?

Back

Preview of the front of card 5
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