Aromatic Chemistry (Benzene) AQA A2 Unit 4

Question & answer flashcards on all the main points you need to know about aromatic chemistry (arenes/benzene) for AQA Unit 4.

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What is the formula of benzene?
C6H6
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What evidence is there to support the delocalised model of benzene?
All C-C bonds are the same length (as there are no alternating C-C and C=C bonds). The enthalpy change data - benzene is far less exothermic than predicted from the Kekule structure (-208 kJ mol-1 instead of -360 kJ mol-1).
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Name this compound: C6H5Cl
Chlorobenzene
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Name this compound: C6H5(OH)
Phenol
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Name this compound: C6H5(NO2)
Nitrobenzene
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Name this compound: C6H5(NH2)
Phenylamine
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Name this compound: C6H5(CH2Cl)
Chloromethylbenzene
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What reaction mechanism does benzene undergo and why?
Electrophilic substitution. The benzene ring is a region of high electron density. The benzene ring is so stable it undergoes substitution reactions to preserve the delocalised ring of electrons.
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Complete the equation and name the reaction: HNO3 + C6H6 --> ?
Nitration. C6H5(NO2) + H2O
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What are the reaction conditions for the nitration of benzene?
WARM benzene with CONCENTRATED HNO3 in the presence of a CONCENTRATED H2SO4 catalyst.
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Write an equation that shows the formation of the nitronium ion that is formed by the catalyst during the nitration of benzene.
HNO3 + H2SO4 --> (NO2)+ + (HSO4)- + H2O
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State some uses of nitration reactions.
Can be reduced to form aromatic amines (which are used in dyes and pharmaceuticals). Used as explosives (e.g. TNT) as nitro compounds decompose violently when heated.
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What are the reaction conditions of Friedel-Crafts acylation (adding an R-C(=O)- group to benzene)?
Heated under reflux, non-aqueous environment with an AlCl3 catalyst present.
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Write an equation for Friedel-Crafts acylation (using RCOCl)
RCOCl + C6H6 --(AlCl3 catalyst, reflux)--> C6H5(COR) + HCl
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Write an equation to show how AlCl3 reacts with RCOCl during acylation of benzene.
RCOCl + AlCl3 --> R-C+=O + AlCl4-
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Write an equation to show how HCl is formed from the product of AlCl3 catalyst reaction and the product of the acylation of benzene.
AlCl4- + H+ --> AlCl3 + HCl
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Other cards in this set

Card 2

Front

What evidence is there to support the delocalised model of benzene?

Back

All C-C bonds are the same length (as there are no alternating C-C and C=C bonds). The enthalpy change data - benzene is far less exothermic than predicted from the Kekule structure (-208 kJ mol-1 instead of -360 kJ mol-1).

Card 3

Front

Name this compound: C6H5Cl

Back

Preview of the front of card 3

Card 4

Front

Name this compound: C6H5(OH)

Back

Preview of the front of card 4

Card 5

Front

Name this compound: C6H5(NO2)

Back

Preview of the front of card 5
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