Chemistry · Edexcel 9CH0 · Paper 2: Advanced Organic and Physical Chemistry · June 2023
This question is about some organic compounds.
Draw the skeletal formula of 1,3‑dimethylcyclohexane.
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A student is asked to devise a laboratory synthesis of 1,2‑dichloroethane. The student suggests reacting ethane with chlorine in the presence of ultraviolet radiation.
Give two reasons why this is not a good method to prepare 1,2‑dichloroethane.
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This question is about alcohols.
Ethanol is a fuel and can be made by either the fermentation of carbohydrates or the hydration of ethene.
How is the ethanol formed by the fermentation of carbohydrates classified?
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Write the equation for the complete combustion of methanol. State symbols are not required.
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Identify, by name or formula, the reagent(s) needed to convert propan‑1‑ol into 1‑iodopropane.
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A sample of pure propan‑2‑ol is analysed using infrared and 13C NMR spectroscopy.
Which of these sets of wavenumber ranges, in cm–1, will be seen in the infrared spectrum of propan‑2‑ol?
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State the number of peaks in the13C NMR spectrum of propan‑2‑ol.
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The equation for the oxidation of ethanol by acidified dichromate(VI) ions is shown.
Deduce the half‑equation for the oxidation of ethanol to ethanoic acid. State symbols are not required.
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This question is about the molar masses of three organic compounds, X, Y and Z.
The accurate relative atomic masses, Ar, of four of the elements that could be present in an organic compound are shown.
| Element | Ar |
| hydrogen, H | 1.0078 |
| carbon, C | 12.0000 |
| nitrogen, N | 14.0031 |
| oxygen, O | 15.9949 |
The mass spectrum of organic compound X gives a molecular ion peak at m / z = 60.0323
What is compound X ?
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9.90 g of a gaseous organic compound, Y, occupies a volume of 5.40 dm3 at room temperature and pressure (r.t.p.).
Calculate the molar mass of the compound Y.
[molar gas volume at r.t.p. = 24.0 dm3mol–1]
(2)
A quantity of a volatile organic liquid, Z, is placed in a 60.0 cm3 flask and heated to 95.0°C. When all the liquid has vaporised, the flask is sealed.
Mass of vapour = 0.170 g
Pressure = 100.6 kPa
Gas constant (R) = 8.31 J mol–1K–1
Calculate the molar mass of compound Z, giving your answer to an appropriate number of significant figures. Assume there was no air left in the flask once the liquid Z had vaporised.
(4)
This question is about some hydrocarbons.
A 2.50 g sample of a hydrocarbon gave 7.59 g of carbon dioxide on complete oxidation.
Calculate the empirical formula of the hydrocarbon.
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Benzene and ethene react with bromine under different conditions but both reactions involve an electrophile.
An electrophile is a substance that
(1)
Explain why benzene is resistant to bromination but ethene reacts readily with bromine at room temperature.
(4)
Nitrogen monoxide reacts with oxygen to form nitrogen dioxide.
The rate is proportional to the concentration of oxygen and to the square of the concentration of nitrogen monoxide.
The rate of this reaction can be determined by measuring the change in the total gas pressure.
Give a reason why this method can be used in this reaction.
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State two factors, other than initial amounts of reactants, that must be kept constant for this method to work.
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The graph shows four lines of a quantity Y plotted against a quantity X.
Which line shows the relationship between the concentration of nitrogen monoxide (Y) and time (X)?
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Which line shows the relationship between rate (Y) and concentration of oxygen (X)?
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The rate of this reaction is zmol dm–3s–1 under certain conditions.
The concentration of nitrogen monoxide is doubled and the concentration of oxygen is halved. All other conditions remain the same.
What will be the new rate of reaction in mol dm–3s–1?
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Nitrogen monoxide is formed in car engines. It is removed by the catalytic converter in the car exhaust.
The reaction is exothermic and the most active catalyst is platinum.
Complete the labelled reaction profile for the catalysed reaction.
(3)
Catalysts, such as platinum, are very expensive.
Explain an economic benefit of using a catalyst in an industrial process.
(2)
Iodine reacts with propanone in acidic conditions.
A student was asked to investigate the kinetics of this reaction. The student predicted that the rate equation for the reaction would be
because the balanced equation shows that one molecule of iodine reacts with one molecule of propanone and the acid is a catalyst.
The student first determined the order of reaction with respect to iodine by keeping the concentrations of propanone and acid constant. The student used the outline procedure shown.
• mix 25 cm3 of aqueous propanone with 25 cm3 of dilute sulfuric acid in a conical flask
• add 25 cm3 of aqueous iodine, immediately start a stopwatch and swirl the mixture in the conical flask
• use a pipette to remove a 10.0 cm3 sample of the solution and place it in a clean conical flask
• add a spatula measure of sodium hydrogencarbonate and note the exact time it is added
• take four more 10.0 cm3 samples of the mixture and add sodium hydrogencarbonate to each of them at regular time intervals
• titrate the unreacted iodine in the samples with sodium thiosulfate solution using starch indicator.
State how the student could ensure that the concentrations of propanone and acid are effectively constant throughout the experiment.
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Explain why sodium hydrogencarbonate is added.
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The student obtained these results.
| Time / min | 5 | 10 | 15 | 20 | 25 |
| Volume of thiosulfate / cm3 | 15.0 | 13.8 | 12.6 | 11.4 | 10.2 |
Give a reason why it is not necessary to calculate the concentration of iodine at each time to work out the order of reaction with respect to iodine.
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(2)
Give a reason why the graph shows that the order of reaction with respect to iodine is zero.
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Further experiments showed that the correct overall rate equation is
Deduce a possible rate determining step in the mechanism of this reaction. Curly arrows are not required.
(2)
Data from two experiments carried out at the same temperature are shown.
| Experiment | [CH3COCH3(aq)] / mol dm–3 | [H+(aq)] / mol dm–3 | [I2(aq)] / mol dm–3 | Rate / mol dm–3s–1 |
| 1 | 3.0 | 0.4 | 0.02 | 3.36 10–5 |
| 2 | 4.0 | 0.2 | 0.04 |
What is the rate, in mol dm–3s–1, in Experiment 2?
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The experiment in (a) is repeated but using aqueous bromine instead of aqueous iodine. All other conditions are kept the same.
Explain how you would expect the rate of reaction of bromination of propanone to compare with the rate of iodination of propanone.
Assume that the reaction between bromine and propanone in acidic conditions has the same rate equation as that between iodine and propanone in acidic conditions.
(2)
This question is about carbonyl compounds.
Ethanal, CH3CHO, and ethanoic acid, CH3COOH, are both soluble in water but ethanoic acid has a much higher boiling temperature than ethanal.
Explain these physical properties of ethanal and ethanoic acid in terms of intermolecular forces.
Include a labelled diagram to show why ethanal is soluble in water.
(4)
Draw the mechanism for this reaction. Include curly arrows and any relevant lone pairs and dipoles.
(4)
Explain whether or not the 2‑hydroxybutanenitrile formed will be a racemic mixture.
(3)
Carbonyl compounds can be identified by reacting them with 2,4‑dinitrophenylhydrazine (2,4‑DNPH) to form a solid derivative. These derivatives have characteristic melting temperatures.
(3)
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This question is about isomerism in organic compounds.
How many structural isomers are there with the formula C5H12?
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Propene reacts with bromine to form 1,2‑dibromopropane as the only product.
Draw the mechanism for the reaction between propene and bromine. Include curly arrows and any relevant lone pairs and dipoles.
(3)
When propene reacts with a mixture of bromine and sodium chloride, it forms 1,2‑dibromopropane, 1‑bromo‑2‑chloropropane and 2‑bromo‑1‑chloropropane but no 1,2‑dichloropropane.
Explain, by reference to your mechanism in (b), why no 1,2‑dichloropropane forms.
(2)
Explain why far more 1‑bromo‑2‑chloropropane forms than 2‑bromo‑1‑chloropropane.
(2)
*(d) Discuss the different types of stereoisomerism that occur in organic compounds. Use only molecules A and B as examples.
Include in your answer:
• how the different types of isomerism arise
• the naming of alkenes with the formula A
• the properties of isomers with the formula B
• diagrams of the different isomers.
(6)
This question is about the analysis of some organic compounds.
A compound A (C3H7Cl) reacts with dilute aqueous sodium hydroxide to produce B (C3H8O). B can be oxidised to C (C3H6O), which cannot be oxidised any further.
A reacts with magnesium in dry ether to give D (C3H7MgCl). When carbon dioxide is passed through the solution of D, followed by acidification, E (C4H8O2) is formed.
Identify the structures of A to E.
(5)
An organic compound, Q, contains carbon, hydrogen and nitrogen only.
When a 1.19 g sample of the compound was heated with sodium hydroxide solution, all of the nitrogen was converted into ammonia. The ammonia was passed into 100.0 cm3 of 0.225 mol dm–3 hydrochloric acid.
25.0 cm3 portions of the resulting solution containing unreacted hydrochloric acid required a mean titre of 15.5 cm3 of 0.100 mol dm–3 sodium hydroxide for neutralisation.
Calculate the percentage of nitrogen in Q.
(5)
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