C27.1 Introduction to arenes AQA A2 Chemistry C27 Aromatic Chemistry Kerboodle Answers : Page No. 176

1 CH

2 3

3 Atoms in the ring rather than being localised in three distinct double bonds.

4

27.2 Arenes — physical properties, naming, and reactivity AQA A2 Chemistry C27 Aromatic Chemistry Kerboodle Answers : Page No. 178

1 Van der Waals forces

2

a 1,3-dichlorobenzene

b 1-bromo-4-chlorobenzen

3 a 1,4-dimethglbenzene

b 1,2-dimethylbenzene

4

R⁺

27.3 Reactions of arenes AQA A2 Chemistry C27 Aromatic Chemistry Kerboodle Answers : Page No. 182

1

a A electrophilic substitution

b A electrophilic substitution

2 1,2-dinitrobenzene and 1,4-dinitrobenzene

3

Addition reactions would involve the loss of aromatic stability.

4

Practice questions: Page No. 183-185

conc HNO₃

conc H₂SO₄

HNO₃ + 2H₂SO₄ → NO₂⁺ + H₃O⁺ + 2HSO₄^–

2

CH₃COCl + AlCl₃ → CH₃⁺CO + AlCl₄^–

Electrophilic substitution

3

CH₃COCl + AlCl₃ → CH₃⁺CO + AlCl₄^–

Electrophilic substitution

4

(a) CH₃CO⁺

(b)

5

(a)

CH₃CH₂COCl OR CH₃CH₂CClO OR propanoyl chloride

OR (CH₃CH₂CO)₂O OR propanoic anhydride

Penalize contradiction in formula and name, e.g., propyl chloride

AlCl₃ or FeCl₃ or names

CH₃CH₂COCl + AlCl₃ → CH₃ CH₂CO⁺ + AlCl₄^–

Allow RCOCl in equation but penalise above

(b)

(c)

Tollens or ammoniacal silver nitrate

6 (a)

(

Benzene is more stable than cyclohexatriene

Because of delocalisation or electrons spread out or resonance

B

conc HNO₃

conc H₂SO₄

2 H₂SO₄ + HNO₃ → 2HSO₄^– + NO₂⁺ + H₃O⁺

7

CH₃CH₂COCl + AlCl₃ → [CH₃CH₂CO]⁺ + AlCl₄^_

8

(4 marks) AQA. 2004

Cyclohexane evolves 120 kJ mol^-1

Therefore expect triene to evolve

360 kJ mol^-1;

or 3 × 120 = 360 kJ mol^-1

360 – 208 = 152 kJ;

Benzene lower in energy / more stable; due to delocalisation;

9

(a)

Nitric acid and sulfuric acid

(b) Explosives / dyes / fibres / pharmaceuticals

(c) (i)

C₆H₆ + HNO₃ → C₆H₅NO₂ + H₂)

(ii) It accepts a pair of electrons

(iii)

Electrophilic substitution.

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