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Date May 2017 Marks available 2 Reference code 17M.2.hl.TZ1.7
Level HL Paper 2 Time zone TZ1
Command term State Question number 7 Adapted from N/A

Question

Benzene is an aromatic hydrocarbon.

Discuss the physical evidence for the structure of benzene.

[2]
a.

State the typical reactions that benzene and cyclohexene undergo with bromine.

M17/4/CHEMI/HP2/ENG/TZ1/07.b

[1]
b.

State the reagents used to convert benzene to nitrobenzene and the formula of the electrophile formed.

[2]
c.

Explain the mechanism for the nitration of benzene, using curly arrows to show the movement of electron pairs.

[4]
d.

State the reagents used in the two-stage conversion of nitrobenzene to aniline.

[2]
e.

Markscheme

Any two of:
planar «X-ray»

C to C bond lengths all equal
OR
C to C bonds intermediate in length between C–C and C=C

all C–C–C bond angles equal

[2 marks]

a.

benzene: «electrophilic» substitution/SE
AND
cyclohexene: «electrophilic» addition/AE

 

Accept correct equations.

[1 mark]

b.

«concentrated» nitric AND sulfuric acids

+NO2

 

Accept NO2+.

[2 marks]

c.

curly arrow going from benzene ring to N of +NO2/NO2+

carbocation with correct formula and positive charge on ring

curly arrow going from C–H bond to benzene ring of cation

formation of organic product AND H+

 

Accept mechanism with corresponding Kekulé structures.

Do not accept a circle in M2 or M3.

Accept first arrow starting either inside the circle or on the circle.

M2 may be awarded from correct diagram for M3.

M4: Accept C6H5NO2 + H2SO4 if HSO4 used in M3.

d.

Fe/Zn/Sn AND HCl/H2SO4/CH3COOH

NaOH/KOH

 

Accept other suitable metals and acids.

Accept other suitable bases.

Award [1 max] for single-step reducing agents (such as H2/Pt, Na2S etc.).

Accept formulas or names.

[2 marks]

e.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.
[N/A]
d.
[N/A]
e.

Syllabus sections

Additional higher level (AHL) » Topic 20: Organic chemistry » 20.1 Types of organic reactions
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Core » Topic 10: Organic chemistry » 10.1 Fundamentals of organic chemistry
Additional higher level (AHL) » Topic 20: Organic chemistry
Core » Topic 10: Organic chemistry
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