Chemistry · Edexcel 9CH0 · Paper 2: Advanced Organic and Physical Chemistry · June 2025
This question is about mass spectrometry.
Which molecule would not give a molecular ion peak with m/z = 74?
(1)
The fragmentation pattern in a mass spectrum can be used to distinguish between structural isomers.
Which m/z peak would be present in the mass spectrum of propanal, CH3CH2CHO, but not in the mass spectrum of propanone, CH3COCH3?
(1)
Intermolecular forces affect the physical properties of compounds.
Which of these isomers, with the formula C8H18, will have the lowest boiling temperature?
(1)
Pentan‑1‑ol and hexane have the same number of electrons but pentan‑1‑ol is much less volatile than hexane.
Explain this difference in volatility.
(2)
Iodine is a solid at room temperature but on gentle heating it vaporises.
What bonds or forces are being broken?
(1)
The boiling temperature of boron trichloride is 13
C while that of phosphorus trichloride is 76
C.
Explain, in terms of the shapes of the molecules, why phosphorus trichloride has a much higher boiling temperature, although both compounds have polar bonds.
Do not consider differences in London forces.
(4)
(1)
What is the IUPAC name for glycerol?
(1)
Covalent bonds can break by either heterolytic fission or homolytic fission.
The reaction of butane and chlorine involves homolytic bond fission of the chlorine molecule, using ultraviolet radiation.
(4)
In the reaction of chlorine with butane, the propagation stage produces two different butyl radicals.
Write the structural formulae of these two radicals.
(2)
The reaction of chlorine with butane produces 2‑chlorobutane (72 %) and 1‑chlorobutane (28 %).
Explain, by application of your knowledge of the stability of carbocations, why there is a higher yield of 2‑chlorobutane.
(2)
Water molecules can undergo either heterolytic fission to form a hydroxide ion or homolytic fission to form a hydroxyl radical.
Draw dot‑and‑cross diagrams of these two species.
Use crosses (×) for oxygen electrons and dots (
) for hydrogen electrons.
(2)
Which process does not involve heterolytic fission?
(1)
The kinetics of the reactions of hydrochloric acid with metal carbonates were investigated using the apparatus shown.
The equation for the reaction is shown.
One student used 0.355 g of calcium carbonate.
Calculate the minimum volume, in cm3, of 0.100 mol dm–3 hydrochloric acid that would completely react with this mass of calcium carbonate. Give your answer to an appropriate number of significant figures.
[Calcium carbonate molar mass = 100.1 g mol–1)
(4)
State why powdered metal carbonate reacts faster than large lumps.
(1)
A second student used 4.19
10–3mol of magnesium carbonate and suggested heating up the apparatus to speed up the rate of reaction.
If the use of heat means that the carbon dioxide gas is at a temperature of 74.0C, then the apparatus shown would not give a measurable result.
Justify this comment by calculating the volume of carbon dioxide gas at this temperature using the ideal gas equation.
Assume that the pressure remains at 100 kPa throughout the experiment.
(4)
The student suggested that the Maxwell–Boltzmann distribution of molecular energies for a reaction mixture at a particular temperature is shown in a graph.
Explain, by adding another line to the graph and by annotating the graph, how heating the reaction mixture results in a faster reaction rate.
(3)
A third student, in order to obtain the rate of reaction, measured the volume of gas produced at various times and used their data to plot the graph shown.
Determine the initial rate of this reaction. You must show your working on the graph. Include units in your answer.
(2)
This question is about benzaldehyde and some related compounds.
*(a) Benzaldehyde (C6H5CHO) can be distinguished from phenylethanone (C6H5COCH3) and benzoic acid (C6H5COOH) using chemical tests.
Describe a series of chemical tests which could be used to distinguish each of these compounds, giving the relevant tests and their positive results.
Do not use tests which give positive results for more than one of these compounds.
Detailed information of the laboratory equipment is not required.
(6)
What is this type of reaction?
(1)
Draw the structure of the organic product of the reaction of 2,4‑DNPH with benzaldehyde.
(1)
This question is about amines.
Aliphatic amines may be prepared from halogenoalkanes or from nitriles.
Assess these two methods for the preparation of butylamine. Consider the reagents, the conditions needed, atom economy and the type of reaction. Include equations.
(7)
Preparation of the aromatic amine, benzene‑1,3‑diamine, requires different conditions.
Write an equation for the preparation of benzene‑1,3‑diamine from the corresponding dinitro‑compound and include necessary conditions.
(3)
Explain the factors affecting the basicity of benzene‑1,3‑diamine and propane‑1,3‑diamine.
Include reference to information given in the table.
| Substance | pKb1 |
| benzene‑1,3‑diamine | 8.89 |
| propane‑1,3‑diamine | 3.83 |
Kb1 is the equilibrium constant for the first protonation reaction.
The equation is shown.
(4)
(3)
The flavour of aniseed and liquorice is mainly due to anethole, which has the structure shown.
Give the molecular formula of anethole.
(1)
Draw the stereoisomer of anethole.
(1)
A structural isomer of anethole is estragole, which has the structure shown.
Give a reason why anethole shows stereoisomerism but estragole does not.
(1)
What is the reagent required to convert anethole to the diol shown?
(1)
The structure of anethole can be drawn with a delocalised model of the benzene ring or with the Kekulé benzene ring structure as shown.
Describe how the orbitals of carbon atoms overlap to form the σ ‑bonds and the π ‑bonds in the delocalised model of the benzene ring. You may include a labelled diagram in your answer.
(3)
Explain why the delocalised model of the benzene ring is the preferred representation rather than the Kekulé cyclic triene. Refer to one physical and one thermodynamic measurement in your answer.
(4)
Anethole is also present in some alcoholic drinks such as the Greek liquor, ouzo.
The anethole is responsible for the so‑called ‘ouzo effect’. This effect is the transparent ouzo liquor turning milky when water is added. The addition of water causes the anethole to form oily droplets which result in a stable milky emulsion.
Deduce the solubility of anethole in ethanol and in water from the ‘ouzo effect’. Justify your answer with reference to the anethole structure shown, but detailed descriptions of intermolecular forces are not required.
(3)
A derivative of anethole is anisaldehyde, which has the structure shown.
What is the number of peaks in the13C NMR spectrum of anisaldehyde?
(1)
Halogenoalkanes are hydrolysed to form alcohols.
The rate constant for the reaction of 1‑bromopropane with aqueous sodium hydroxide was determined at five temperatures. Some of the results are given in the table.
| Temperature (T) / K | 1/Temperature (1/T) / K–1 | Rate constant (k) / dm3mol–1s–1 | lnk |
| 298 | 3.36 10–3 | 1.3610–4 | –8.9 |
| 3.2910–3 | –8.4 | ||
| 308 | 3.25 10–3 | 3.0410–4 | –8.1 |
| 318 | 3.1410–3 | 6.7610–4 | –7.3 |
| 328 | 3.0610–3 | 1.2310–3 | –6.7 |
Complete the table of data.
(2)
Plot a graph of ln k against 1/ T and use it to determine the activation energy, Ea, for this reaction in kJ mol–1.
You must show your working on the graph and include the value of the gradient of the line and its units.
The Arrhenius equation can be expressed as
Activation energy........
(5)
The rate constant for the reaction of 1‑bromopropane with aqueous potassium hydroxide has the units of dm3mol–1s–1.
Explain why it can be deduced that the reaction is second order overall. Assume that the units of the rate of reaction are mol dm–3s–1.
(2)
The rate of reaction for the hydrolysis of 2‑bromo‑2‑methylpropane by aqueous hydroxide ions is independent of the concentration of hydroxide ions.
Draw the SN1 reaction mechanism for this hydrolysis. Include curly arrows and any relevant dipoles and lone pairs of electrons.
(3)
State how your mechanism is consistent with the rate of reaction being independent of hydroxide ion concentration.
(1)
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