11.4 Arenes, Set A To print: Ctrl + P, paper A4, margins Default.
Learners' AlleyDesigned by Khow Willard
11.4
Arenes
Set AFoundations
Name
Time 1 hour
Total 36 marks
A Data Booklet may be used.
A
From the lesson
13 marks
1
CommonGive the reagents and conditions to make each compound from benzene.
(a)
bromobenzene
[1]
(b)
ethylbenzene
[1]
Source: Learners' Alley, Arenes slides
2
ChallengeWrite the equation that forms the electrophile in question 1(a).
[1]
Source: Learners' Alley, Arenes slides
3
CommonMethylbenzene reacts with Br2. Give the conditions and organic product for
(a)
substitution on the ring
[2]
(b)
substitution on the side chain
[2]
Source: Learners' Alley, Arenes slides
4
Why does benzene undergo substitution, not addition?
[1]
Source: Learners' Alley, Arenes slides
5
What is the electrophile in nitration, and how is it formed?
[2]
Source: Learners' Alley, Arenes slides
6
Why is methylbenzene nitrated faster than benzene?
[2]
Source: Learners' Alley, Arenes slides
7
Why doesn't tert-butylbenzene react with hot acidified KMnO4?
[1]
Source: Learners' Alley, Arenes slides
B
Practice
23 marks
8
CommonIn the reaction represented by the equation C6H6 + Cl2 → C6H5Cl + HCl, what type of reaction has benzene undergone?
Aelectrophilic addition
Belectrophilic substitution
Cfree radical substitution
Dnucleophilic addition
Enucleophilic substitution
Answer [1]
Source: A Level 1993 P4 Q21, via EJC Arenes Topical Quiz, Q5
9
The molecule of benzene, C6H6, is a regular hexagon in which the π electrons are described as delocalised. Which of the following statements support this structure?
1Benzene is a good conductor of electricity.2Addition reactions of benzene take place more easily than substitution.3All C–C bond lengths in benzene are intermediate between the C–C bond in an alkane and the C=C bond in an alkene.4The enthalpy change of hydrogenation of benzene is less exothermic than that predicted for cyclohexatriene.
A1 and 3
B3 and 4
C1, 2 and 3 only
D1, 2 and 4 only
Answer [1]
Source: SRJC 2017 Prelim P1 Q22, via EJC Arenes Topical Revision, Q4
10
A comparison is made of the nitration reactions of some aromatic compounds. How will the reaction temperatures required compare?
lowest
highest
A
benzoic acid
benzene
phenylamine
B
phenylamine
benzene
ethylbenzene
C
phenylamine
ethylbenzene
benzaldehyde
D
benzoic acid
benzaldehyde
ethylbenzene
A
B
C
D
Answer [1]
Source: DHS 2017 Prelim P1 Q18, via EJC Arenes Topical Revision, Q9
11
(a)
CommonState the reagents and conditions needed to convert benzene into (i) chlorobenzene, (ii) bromobenzene, (iii) nitrobenzene.
[3]
(b)
The nitration of benzene is a two-step reaction: C6H6 + A+ → B → C6H5NO2 + H+. Identify the cation A+.
[1]
(c)
The position of substitution during the electrophilic substitution of arenes is determined by the nature of the group already attached to the ring. Suggest a likely structure for the organic product of each reaction: (i) bromination of (ii) chlorination of
[2]
Source: A Level 2004 P4 Q5, via EJC Arenes Topical Quiz, Q2
12
Describe a simple chemical test to distinguish the following pairs of compounds. State your observations and give balanced equations for the reactions involved.
(a)
benzene and methylbenzene
[2]
(b)
benzene and cyclohexane
[2]
Source: EJC 2022 JC1 Arenes Tutorial, Section B Q5(a) and (b)
13
CommonBrCl reacts with benzene in the presence of AlCl3 in an electrophilic substitution reaction to produce bromobenzene.
(a)
Explain why bromobenzene is made in preference to chlorobenzene during the reaction.
[1]
(b)
Hence, draw the electrophilic substitution mechanism of the reaction.
[2]
Source: 2025 NYJC J2 Prelim P3 QA1(c)(i) and (ii)
14
ChallengeMethylbenzene, C6H5CH3, is required on a large scale as an industrially important organic compound, and is also added to high grade unleaded petrol.
(a)
Write an equation for the combustion of methylbenzene.
[1]
(b)
Methylbenzene is manufactured by passing heptane, C7H16, vapour over a catalyst. In the process, there is one gaseous by-product. Construct an equation for this process, showing the structural formulae of the organic molecules.
[1]
(c)
The reaction is endothermic. Explain what conditions of temperature would favour a high equilibrium yield.
[2]
(d)
Use the equation in (b) to explain what conditions of pressure would favour a high equilibrium yield.
[2]
(e)
1,4-dimethylbenzene can be oxidised to benzene-1,4-dicarboxylic acid. Using the [O] notation for the oxidation of organic compounds, write a balanced equation for this oxidation.
[1]
Source: A Level 1997 P2 Q5 (a) to (d) and (f), via EJC Arenes Topical Quiz, Q4