3.10 Aromatic Chemistry

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Total cards: 24•Content version: v4•Public deck•Updated: 8/1/2026

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Front (Question)

Arenes

Back (Answer)

Compounds containing a benzene ring

Front (Question)

Evidence against the Kekule structure

Back (Answer)

• Benzene doesn’t decolourise bromine water • C-C bond lengths are all equal in benzene • Thermochemical data for the hydrogenation of benzene show it is more stable that the Kekule structure

Front (Question)

Does benzene decolourise bromine water?

Back (Answer)

Not at room temperature. (The reaction will occur at much higher temperatures than for alkenes)

Front (Question)

Which has the larger bond length: C-C OR C=C

Back (Answer)

C-C

Front (Question)

Bond lengths in benzene

Back (Answer)

• All equal • Between C-C and C=C

Front (Question)

ΔH of hydrogenation of cyclohexene

Back (Answer)

-120kJ/mol

Front (Question)

ΔH of hydrogenation of Kekule structure of benzene

Back (Answer)

-360kJ/mol

Front (Question)

ΔH of hydrogenation of benzene

Back (Answer)

-208kJ/mol

Front (Question)

Name for the energy difference between hydrogenation of benzene and the kekule structure of benzene

Back (Answer)

Delocalisation energy

#10

Front (Question)

How are pi bonds formed in benzene?

Back (Answer)

• Each C has an unbonded electron in a p-orbital • Adjacent p-orbitals overlap • Forms a pi bond above and below the ring

#11

Front (Question)

Electrons in the pi bond in benzene are ……

Back (Answer)

delocalised

#12

Front (Question)

Why is benzene more stable than the kekule structure?

Back (Answer)

Pi bonds are harder to break that C=C bonds

#13

Front (Question)

Why are some cyclic dienes more stable than others?

Back (Answer)

The dienes where the pi bonds adjacent are more stable as the electrons in these bonds become delocalised

#14

Front (Question)

Phenol

Back (Answer)

A benzene ring with an OH group attached (This is not an alcohol but has many similar reactions)

#15

Front (Question)

Why are benzene rings susceptible to attack from electrophiles?

Back (Answer)

The pi bond is an area of high electron density

#16

Front (Question)

Why does benzene have substitution reactions rather than addition reactions?

Back (Answer)

This preserves the stability of the benzene ring

#17

Front (Question)

Mechanism for nitration of benzene

Back (Answer)

Electrophilic substitution

#18

Front (Question)

Reagents for nitration of benzene

Back (Answer)

• Conc. nitric acid • Conc. sulfuric acid (catalyst)

#19

Front (Question)

Conditions for the nitration of benzene

Back (Answer)

60°C

#20

Front (Question)

Requirements for further substitution (nitration of benzene)

Back (Answer)

• Excess of nitric acid • Higher temperatures (above 60°C)

#21

Front (Question)

Electrophile for the nitration of benzene

Back (Answer)

⁺NO₂ (nitronium ion)

#22

Front (Question)

Equation for generation of a nitronium ion

Back (Answer)

HNO₃ + H₂SO₄ –> ⁺NO₂ + HSO₄⁻ + H₂O

#23

Front (Question)

Reagents for the acylation of benzene

Back (Answer)

Acyl chloride and anhydrous aluminum chloride (catalyst)

#24

Front (Question)

Anhydrous aluminum chloride

Back (Answer)

AlCl₃