OCR A Level Chemistry A Synthesis and analytical techniques June 2025 question paper H432/02

Which compound is alicyclic and unsaturated?

The skeletal structure of a medicinal drug is shown below.

How many hydrogen atoms are in its molecular formula?

0.200 mol of HOOCCH₂CH₂COOH is reacted with 0.300 mol NaOH.

How many water molecules are formed?

A 1.204 × 10²³

B 1.806 × 10²³

C 2.408 × 10²³

D 3.612 × 10²³

What are the organic products of the acid hydrolysis of CH₃CH₂CONHCH₃?

A CH₃CH₂COO^– + CH₃NH₃⁺

B CH₃CH₂COOH + CH₃NH₃⁺

C CH₃CH₂COOH + CH₃NH₂

D CH₃CH₂COO^– + CH₃NH₂

Ethene can be reacted with hydrogen bromide.

Which statement about this reaction is correct?

A H – acts as a nucleophile.

B Br + acts as an electrophile.

C H⁺— Br^– acts as an electrophile.

D H⁺— Br^– acts as a nucleophile.

Which reagents could a student use to prepare the ester shown?

How many stereoisomers does the compound CH₃CH(Br)CH=CHCH(Cl)CH₃ have?

A 2

B 4

C 6

D 8

Which molecule does not produce a mass spectrum containing a peak at m / z = 29?

Which process does not involve infrared radiation?

A Catalytic ozone depletion

B Monitoring toxic gases in the air

C Measuring ethanol in breathalyser tests

D Global warming

Which molecule(s) would form a ketone group when oxidised?

A 1, 2 and 3

B Only 1 and 2

C Only 2 and 3

D Only 1

The structure of vitamin C is shown.

Which reagent(s) will react with vitamin C?

1 Aqueous bromine water

2 Acidified potassium dichromate(VI)

3 Aqueous silver nitrate in ethanol

A 1, 2 and 3

B Only 1 and 2

C Only 2 and 3

D Only 1

Which compound(s) has/have three peaks in their¹³C NMR spectrum?

A 1, 2 and 3

B Only 1 and 2

C Only 2 and 3

D Only 1

This question is about hydrocarbons with six carbon atoms.

Compound A is a hydrocarbon:

Compound A

What is the systematic name of compound A ?

The table below shows incomplete information about two hydrocarbons.

Complete the table.

Compound B, CH₃CH=C(CH₃)CH₂CH₃, exists as E and Z stereoisomers.

Draw the structures of the E and Z stereoisomers of compound B.

Explain why compound B can form E and Z stereoisomers.

Hexane, C₆H₁₄, is used as a fuel.

1.0 mol of hexane is mixed with 6.0 mol of oxygen and combusted.

Construct an equation for the incomplete combustion of 1.0 mol of hexane with 6.0 mol of oxygen.

1-Chlorobut-2-ene and 3-hydroxybutanoic acid can both form polymers.

Draw two repeat units of each of the polymers formed.

State the type of polymerisation reaction that takes place for each compound.

The disposal of polymers containing chlorine is a major challenge.

Suggest why a polymer made from monomers containing chlorine, such as 1-chlorobut-2-ene, is difficult to dispose of by incineration.

The polymer formed from 3-hydroxybutanoic acid can be hydrolysed. This makes the polymer biodegradable.

Suggest what feature in the structure of this polymer allows this hydrolysis.

This question is about reactions of haloalkanes.

Haloalkanes can react with potassium cyanide to form new carbon–carbon bonds.

Outline the mechanism for the reaction of 2-bromopropane with cyanide ions.

Show curly arrows, relevant dipoles and products.

Name this type of mechanism.

The table below shows the boiling points of propan-1-ol and 1-bromopropane.

Propan-1-ol can be reacted to form 1-bromopropane.

Suggest suitable reagents for this reaction.

The reaction to form 1-bromopropane from propan-1-ol is carried out in a flask.

After the reaction, the flask contains a mixture of an organic layer (density = 1.35 g cm^–3) and an aqueous layer (1.04 g cm^–3).

Describe how to obtain pure 1-bromopropane from the mixture.

This question is about aromatic compounds.

The diagrams show the Kekulé and delocalised models of benzene.

Kekulé Delocalised

One piece of evidence for the delocalised model is that benzene does not decolourise aqueous bromine.

Suggest two other pieces of evidence which support the delocalised model of benzene.

A student investigates the reactions of benzene and phenol with excess bromine.

The student’s observations are given in Table 20.1.

Table 20.1

Explain the difference in the relative reactivities of benzene and phenol with bromine.

The white precipitate has a relative molecular mass of 330.7.

Construct an equation for the reaction of phenol with excess bromine shown in Table 20.1.

Show the structure of the organic species.

Compound G is an organic compound used in the production of pesticides.

Compound G can be synthesised from benzene in the two-stage process shown.

Synthesis 1

Benzene
Methylbenzene
Compound G

Suggest a reagent and halogen carrier that could be used in Stage 1 of Synthesis 1.

Stage 2 of Synthesis 1 is the conversion of methylbenzene to compound G.

Outline the mechanism for the reaction in Stage 2.

Show the role of H₂SO₄ as a catalyst.

A student suggested an alternative two-stage synthesis of compound G from benzene.

Synthesis 2

Benzene
Nitrobenzene
Compound G

When Synthesis 2 is attempted, the synthesis is not successful and a different organic compound from compound G is produced.

• Suggest why Synthesis 1 is successful but Synthesis 2 is not successful.

• Suggest the structure of the different organic compound that is formed in Synthesis 2.

In the production of a pesticide, compound G is reduced to amine H.

Suggest suitable reagents and complete the equation for this reduction.

Reagents........

Equation:

Compound G
Amine H

This question is about carbonyl compounds.

The three compounds below each contain a ketone and one other functional group.

Pyruvic acid
Methylglyoxal
Acetol

What is a functional group ?

A chemical test is carried out which gives a positive result for all three compounds.

Suggest the reagent and observation of this chemical test.

Reagent........

Observation........

A student is provided with three unlabelled sample tubes, containing either pyruvic acid, methylglyoxal or acetol.

The student carries out three chemical tests on each sample.

Complete the table with the expected observations, including ‘no change’ where appropriate.

Complete the flowchart for the reactions of pyruvic acid.

This question is about organic acids.

-Amino acids have the general formula RCH(NH₂)COOH.

Compound S is made of two -amino acids bonded together.

Compound S is hydrolysed into its component -amino acids.

The resulting mixture is analysed using TLC to produce a chromatogram:

The R group and the R_f value is shown for some -amino acids.

Determine the R_f values of the two -amino acids in the chromatogram.

Compound S has two possible structures.

Draw both of these structures.

This part is about compounds called -keto acids.

The equation shows the decomposition of a -keto acid.

Draw the structures of the organic products you would expect from the decomposition of the two other -keto acids below.

-Amino acids have the NH₂ group bonded to the carbon atom adjacent to the carboxylic acid group.

Suggest the difference between an -keto acid and a -keto acid.

This question is about spectral analysis.

Compound K, C₄H₁₀O, is refluxed with H₂SO₄ to form a mixture of compound L and compound M.

The infrared spectrum of compound K is shown.

Compound L and compound M are analysed using¹³C NMR spectroscopy.

• The¹³C NMR spectrum of compound L has 4 peaks.

• The¹³C NMR spectrum of compound M has 2 peaks.

Suggest the functional group in compound K, showing your reasoning, and suggest possible structures for compound K, compound L and compound M.

Functional group........

* An unknown organic compound N is analysed and produces the following results.

Elemental analysis by mass

C, 62.07%; H, 10.34%; O, 27.59%

Mass spectrum

The numbers by the peaks are the relative peak areas.

Determine the structure of the compound N, showing all your reasoning.