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Pearson Edexcel International Advanced Level

Friday 17 January 2025
Afternoon (Time: 1 hour 45 minutes) Paper
reference WCH15/01
Chemistry  

International Advanced Level

UNIT 5: Transition Metals and Organic
Nitrogen Chemistry

You must have: Total Marks

Scientific calculator, Data Booklet, ruler

Instructions
•• Use black ink or ball‑point pen.
If pencil is used for diagrams/sketches/graphs it must be dark (HB or B).
• Fill in the boxes at the top of this page with your name,
centre number and candidate number.
•• Answer all questions.
Answer the questions in the spaces provided
– there may be more space than you need.

Information
•• The total mark for this paper is 90.
The marks for each question are shown in brackets
– use this as a guide as to how much time to spend on each question.
• structure
In the question marked with an asterisk (*), marks will be awarded for your ability to
your answer logically, showing how the points that you make are related or
follow on from each other where appropriate.
• A Periodic Table is printed on the back cover of this paper.
Advice
•• Read each question carefully before you start to answer it.
Show all your working in calculations and include units where appropriate.
•• Try to answer every question.
Check your answers if you have time at the end.
Turn over

P78459A
©2025 Pearson Education Ltd.
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 SECTION A

Answer ALL the questions in this section.

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You should aim to spend no more than 20 minutes on this section.

For each question, select one answer from A to D and put a cross in the box . If you change
your mind, put a line through the box and then mark your new answer with a cross .

1 Which species cannot act as a ligand in the formation of a complex ion?

A C2H6

B CO

C OH–

D C4H9NH2
(Total for Question 1 = 1 mark)

2 An aqueous solution of a transition metal ion absorbs frequencies of light

corresponding to green, yellow and red.
Which ion is likely to be in the solution?

A Mn2+

B Co2+

C Ni2+
D Cu2+
(Total for Question 2 = 1 mark)

3 The first five ionisation energies of four elements are shown.

Which are the ionisation energies of a transition metal?

A 419 3051 4412   5877   7975

B 578 1817 2745 11 578 14 831

C 738 1451 7733 10 541 13 629

D 758 1646 3232   4950   7671

(Total for Question 3 = 1 mark)
Use this space for any rough working. Anything you write in this space will gain no credit.

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 4 What is the colour of the VO2+ ion in aqueous solution?

A blue
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B green

C violet

D yellow
(Total for Question 4 = 1 mark)

5 Which statement about a catalytic converter used to reduce toxic emissions from
internal combustion engines is not true?

A the catalyst contains platinum

B CO and NO are absorbed by the catalyst

C after the reaction, desorption of CO2 and N2 takes place

D it is a heterogeneous catalytic reaction

(Total for Question 5 = 1 mark)

6 Which of these pairs of elements are both transition metals?

A gold and scandium

B gold and titanium

C scandium and zinc

D titanium and zinc
(Total for Question 6 = 1 mark)

7 What are the shapes of the complexes [CuCl4]2– and Pt(NH3)2Cl2?

[CuCl4]2– Pt(NH3)2Cl2
A square planar square planar
B square planar tetrahedral
C tetrahedral square planar
D tetrahedral tetrahedral

(Total for Question 7 = 1 mark)

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8 Which is correct about standard electrode potentials?

A E cell
d
is proportional to ln K and ln ΔS total

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B E cell
d
is proportional to ln K and ΔS total

C ln E cell
d
is proportional to K and ΔS total

D E cell
d
is proportional to ln K and ΔS surroundings
(Total for Question 8 = 1 mark)

9 (a) Which reagents are mixed with hydrochloric acid to produce the
benzenediazonium ion?

+
N N

benzenediazonium ion
(1)
A C6H5NH2 and NaNO2
B C6H5NO2 and NaNO2

C C6H5NO2 and NaNO3

D C6H5NH2 and NaNO3

(b) Which reagents and conditions are used to prepare the yellow dye
4‑phenyldiazenylphenol from the benzenediazonium ion?

N N
+
N N

OH
benzenediazonium ion 4‑phenyldiazenylphenol
(1)
A phenol dissolved in an acid solution at 25 °C

B phenol dissolved in an alkaline solution at 25 °C

C phenol dissolved in an acid solution at 5 °C

D phenol dissolved in an alkaline solution at 5 °C

(Total for Question 9 = 2 marks)

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 10 Which sequence describes recrystallisation?

A d
 issolve in the minimum volume of cold solvent, filter to remove the
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insoluble impurities, then add hot solvent and filter to remove the
soluble impurities

B d
 issolve in the minimum volume of hot solvent, filter to remove the soluble
impurities, wash with cold solvent to remove the insoluble impurities

C d
 issolve in the minimum volume of hot solvent, filter to remove the
insoluble impurities, then cool and filter to remove the soluble impurities

D d
 issolve in the minimum volume of hot solvent, filter to remove the soluble
impurities, then cool and filter to remove the insoluble impurities
(Total for Question 10 = 1 mark)

11 A synthesis of aspirin from phenol is shown.

OH OH OCOCH3

CO2H CO2H
Step 1 Step 2
yield 80% yield 75%

phenol, Mr = 94 aspirin, Mr = 180

What mass of aspirin is formed from 23.5 g of phenol?

A 14.1 g

B 27.0 g

C 33.8 g

D 36.0 g
(Total for Question 11 = 1 mark)

12 An 8.4 g sample of a hydrocarbon formed 26.4 g of carbon dioxide on complete

combustion. What is the molecular formula of this compound?

A CH2

B C6H6

C C2H6

D C6H12
(Total for Question 12 = 1 mark)

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13 What are the volumes of oxygen required and carbon dioxide produced, at room
temperature and pressure (r.t.p.), on complete combustion of 5.8 g of butane, C4H10?

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[Molar volume of a gas at r.t.p. = 24.0 dm3 mol–1 Mr C4H10 = 58.0]

volume of oxygen volume of carbon dioxide

/ dm3 / dm3
A 15.6 9.6
B 12.0 9.6
C 21.6 2.4
D 15.6 12.0

(Total for Question 13 = 1 mark)

Use this space for any rough working. Anything you write in this space will gain no credit.

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 14 What is the repeat unit of the water‑soluble polymer poly(ethenol)?

( (
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OH H

A C C

H OH

( (
H H

B C C

H OH

( (
H OH

C C C

H OH

( (
OH OH

D C C

OH OH

(Total for Question 14 = 1 mark)

15 A repeat unit for a polyamide is shown.

H H
N N (CH2)4
(CH2)6 C C

O O

Which pair of monomers makes this polymer?

A H2N(CH2)6NH2 and HOOC(CH2)4COOH

B NC(CH2)6CN and HOOC(CH2)4COOH

C H2N(CH2)4NH2 and HOOC(CH2)6COOH

D H2N(CH2)6NH2 and HO(CH2)6OH

(Total for Question 15 = 1 mark)

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16 Four compounds (W, X, Y and Z) are shown.

CH3

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W C H
HOOC CH3

CH3

X C NH2
HOOC CH3

CH3

Y C NH2
HOOC H

COOH

Z C NH2
HOOC CH3

(a) Which compound is an optically active amino acid?

(1)
A compound W

B compound X
C compound Y

D compound Z

(b) Which compound does not have the same number of peaks in the low‑resolution
proton NMR spectrum and in the 13C NMR spectrum?
(1)
A compound W

B compound X

C compound Y

D compound Z
(Total for Question 16 = 2 marks)

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9
*P78459A0932*
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17 Asparagine is an amino acid.

O NH2

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C

CH2
H2N C COOH
H

asparagine

(a) What will be the structure of asparagine in an aqueous solution at pH 2?

(1)

O NH2
C

A CH2
H2N C COOH
H

O NH2
C

B CH2
+
H3N C COO–
H

H+
O NH2
C
C CH2
+
H3N C COOH
H

O NH2
C

D CH2
+
H3N C COOH
H

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 (b) In a high‑resolution proton NMR spectrum of asparagine, what would be the
splitting pattern for the protons indicated by the arrow?
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O NH2
C

CH2
H2N C COOH
H
(1)
A singlet

B doublet

C triplet

D quartet
(Total for Question 17 = 2 marks)

TOTAL FOR SECTION A = 20 MARKS

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 SECTION B

Answer ALL the questions. Write your answers in the spaces provided.

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18 The standard emf, E cell
d
, of the cell shown was measured.

A
zinc electrode B

solution containing Zn2+(aq)

C

Electrode system Standard electrode potential E d /V

Zn2+(aq) + 2e–  Zn(s) –0.76

Fe3+(aq) + e–  Fe2+(aq) +0.77

(a) (i) Identify, by name or formula, the substances needed in the salt bridge and the
right‑hand half‑cell. Include concentrations where appropriate.
(4)
A Salt bridge containing a solution of the compound

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B Electrode made of

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C Solution containing the compounds

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 (ii) State why a salt bridge is used rather than a wire.
(1)
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(b) Write an equation for the reaction that would take place if current was allowed to
flow through the circuit. State symbols are not required.
(2)

d
(c) Under standard conditions, the E cell for this reaction is +1.53 V.
State what would happen to this value, if anything, when the Zn2+ solution in the
half‑cell is diluted. Justify your answer.
(2)

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(Total for Question 18 = 9 marks)

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19 Grignard reagents are used to increase the length of the carbon chain in
organic molecules.

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An outline synthesis of propanoic acid from ethanoic acid is shown.

H O H H
Step 1 Step 2
H C C H C C O H Compound X
H O H H H
Step 3
Step 4
propanoic acid Grignard reagent

Complete the table.

Step 1 reagent(s) and conditions

Step 2 reagent(s)

Name or formula of compound X

Step 3 reagent(s) and conditions

Formula of the Grignard reagent

Step 4 reagent(s)

(Total for Question 19 = 6 marks)

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*P78459A01532*
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20 This question is about some chromium compounds.

(a) Some reactions of chromium compounds are shown.

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CrO42–(aq)
yellow

Reaction 4 OH–(aq) H+(aq)

Reaction 1
Reaction 3
2–
H2O2(aq)
Cr2O (aq) 7 Cr3+(aq)
orange Y
green/grey excess
Reaction 2 purple
metal, M, aqueous aqueous
and acid ammonia solution

(i) Write the equation for Reaction 1. Use the half‑equations from page 10 of
your Data Booklet. State symbols are not required.
(2)

(ii) In Reaction 2, Cr2O72– reacts with a metal, M, in acid conditions forming

Cr3+ and M2+.
d
Identify a possible metal, M, calculating E cell for its reaction with Cr2O72–.
Use information from page 10 of your Data Booklet.
(2)

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(iii) Give the formula of the species responsible for the purple colour formed in
Reaction 3, naming the type of reaction that occurs.
(2)

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*P78459A01632* 
 (iv) State whether or not the reaction in Reaction 4 is a redox reaction.
Justify your answer using oxidation numbers.
(2)
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(b) A double salt of chromium contains Cr3+, K+ and SO42– ions.

(i) Deduce the simplest formula of this double salt.
(1)

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(ii) The double salt also exists as hydrated crystals.

When a sample of the hydrated double salt is heated until all the water of
crystallisation is removed, 56.74 % of the original mass of solid remains.
Calculate the number of moles of water of crystallisation in one mole of the
hydrated double salt.
(4)

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 (c) We require small amounts of chromium(III) ions, Cr3+, in our diet as they are
important in the breakdown of fats, and many other body processes.
However, too high a concentration of Cr3+ is toxic.

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Blood should not contain more than 4 parts per billion by mass of Cr3+.
The concentration of Cr3+ in a blood sample was 1.345 × 10–7 mol dm–3.
(i) Show, by calculation, that the Cr3+ level in this blood sample exceeds the
safe limit.
[1 billion = 1 × 109 Assume the density of blood is 1.0 g cm–3 ]
(2)

(ii) EDTA4– has been considered as a potential treatment for Cr3+ poisoning.

O
–
O O
–
O
N
:

N
:

O–
–
O O

O
EDTA4–

Suggest how EDTA4– would act to treat Cr3+ poisoning, giving a reason why
EDTA4– would be preferred to other reagents such as 1,2‑diaminoethane,
NH2CH2CH2NH2 .
(2)

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................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(Total for Question 20 = 17 marks)

18
*P78459A01832* 
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21 This question is about iron(II) sulfate, FeSO4.
(a) (i) The electronic configuration for Fe is shown.

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(1)

Fe [Ar]

3d 4s

Complete the electronic configuration for the Fe2+ ion in iron(II) sulfate.

Fe2+ [Ar]

3d 4s

(ii) An aqueous solution of iron(II) sulfate is pale green in colour.

When left exposed to the air the solution turns brown.
Explain why this colour change occurs. In your response refer to your answer
from (a)(i).
(3)

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................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

20
*P78459A02032* 
 (b) Many moss killers contain iron(II) sulfate, FeSO4, as the active compound.
Potassium manganate(VII) can be used to determine the amount of
iron(II) sulfate present.
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In an experiment, 6.42 g of moss killer was transferred to a volumetric flask and

made up to 250 cm3 with distilled water. A 25.0 cm3 portion of this solution was
acidified and titrated with 0.00740 mol dm–3 potassium manganate(VII) solution.
The equation for the titration is shown.

5Fe2+(aq) + MnO4–(aq) + 8H+(aq) → Mn2+(aq) + 5Fe3+(aq) + 4H2O(l)

The mean titre was 17.70 cm3.

Calculate the percentage, by mass, of iron(II) sulfate in the moss killer.
Give your answer to an appropriate number of significant figures.
[Molar mass FeSO4 = 151.9 g mol–1]
(6)

21
 *P78459A02132* Turn over
 (c) Suggest why iron(II) sulfate is acidic when dissolved in water.
(2)

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................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(Total for Question 21 = 12 marks)

22
*P78459A02232* 
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*22 Compare and contrast the bromination of benzene and the bromination of phenol.
Include equations in your answer.

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Detailed mechanisms are not required.
(6)

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................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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24
*P78459A02432* 
 ................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(Total for Question 22 = 6 marks)

TOTAL FOR SECTION B = 50 MARKS

25
 *P78459A02532* Turn over
 SECTION C

Answer ALL the questions. Write your answers in the spaces provided.

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23 Local anaesthetics in dentistry
Procaine is a local anaesthetic that was commonly used until the end of the last
century in dental procedures to numb the area around a tooth.

N
O

H2N

procaine

(a) Deduce the molecular formula of procaine.

(1)

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26
*P78459A02632* 
 (b) A possible reaction sequence to make procaine is shown.

O Cl
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CH3 CH3 COOH

C

Step 1 Step 2 Step 3 Step 4

NO2 NO2 NO2

Step 5

O O
Step 6
N N
O O

H2N O 2N

(i) Identify, by name or formula, the two reagents needed for Step 1.
(2)

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................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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 (ii) For Step 2, draw the mechanism for this reaction, including the formation of a
suitable electrophile and the regeneration of the catalyst.
Include curly arrows.

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(5)

(iii) For Step 5, name the type of reaction taking place and draw the
skeletal formula of the reagent needed to carry out this reaction.
(2)
Type of reaction

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Skeletal formula of the reagent

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 (iv) Identify, by name or formula, the reagents required for Step 6.
(1)
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(c) Procaine contains two nitrogen atoms, one of which is a stronger base than
the other.

N
O

H2N

procaine

(i) Explain why the basicity of the nitrogen atoms in procaine is different.
(3)

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................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(ii) Procaine hydrochloride is made by reacting procaine with hydrogen chloride

in a 1 : 1 ratio.
Draw the structure of procaine hydrochloride, showing how the hydrogen ion
attaches to the molecule.
(1)

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 (iii) Explain why procaine hydrochloride is more soluble in aqueous solutions such
as blood plasma than procaine.
(2)

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................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(d) Nowadays, procaine has been replaced by lidocaine, a related compound, as a

local anaesthetic in dentistry.
Lidocaine is supplied in 2.2 cm3 cartridges that contain 44 mg of lidocaine.
A typical adult dose is 1.5 cm3.
Calculate the number of molecules of lidocaine present in a 1.5 cm3 dose.
[Molar mass lidocaine = 234 g mol–1 ]
(3)

(Total for Question 23 = 20 marks)

TOTAL FOR SECTION C = 20 MARKS

TOTAL FOR PAPER = 90 MARKS
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