Edexcel A Level Chemistry Paper 2: Advanced Organic and Physical Chemistry June 2024 question paper 9CH0/02

This question is about organic compounds that contain a halogen atom or a nitrogen atom.

Equal amounts of four bromoalkanes were added to separate test tubes containing 2 cm³ of a silver nitrate solution. The mixtures were heated in a water bath.

Which bromoalkane would be the first to form a precipitate?

Which pair of reactants will form an N ‑substituted amide?

Ammonia reacts with bromoethane as shown.

Explain, by referring to the reaction mechanism, the roles of ammonia in the formation of each of the products of this reaction.

What conditions are needed for this reaction?

The halogenoalkane, 1‑bromobutane, can be formed by the reaction of butan‑1‑ol with sodium bromide and sulfuric acid.

Calculate the atom economy, by mass, for the formation of 1‑bromobutane. Give your answer to one decimal place.

[A_r values: H = 1.0 C = 12.0 O = 16.0 Na = 23.0 S = 32.1 Br = 79.9]

This question is about Grignard reagents.

A Grignard reagent is formed by reacting bromoethane with magnesium under reflux.

The most suitable solvent for this reaction is

State the use of Grignard reagents in organic synthesis.

In their reactions, the Grignard reagent is best described as

Grignard reagents must be kept dry.

Predict the organic product that forms when CH₃CH₂MgBr reacts with water. Justify your answer by considering the polarity of both CH₃CH₂MgBr and water.

Which compound will form a tertiary alcohol when it reacts with a Grignard reagent, followed by acid hydrolysis?

This question is about hydrogen peroxide, H₂O₂.

Draw a dot‑and‑cross diagram of a molecule of hydrogen peroxide.

Hydrogen peroxide decomposes to form water and oxygen.

Explain, using oxidation numbers, why the decomposition of hydrogen peroxide is classified as a disproportionation reaction.

The decomposition of hydrogen peroxide is catalysed by iodide ions, I^–(aq).

The kinetics of this reaction were investigated using different concentrations of hydrogen peroxide and iodide ions. The results are shown in the table.

Experiment	[H2O2(aq)] / mol dm–3	[I–(aq)] / mol dm–3	Rate / mol dm–3s–1
1	0.100	0.0500	8.9010–7
2	0.400	0.0500	3.5610–6
3	0.200	0.100	3.5610–6

Deduce the order of reaction with respect to hydrogen peroxide and to iodide ions.

Order with respect to hydrogen peroxide_........

Order with respect to iodide ions_........

Write the rate equation for the reaction using your answer to (c)(i).

Calculate the rate constant, k, using data from Experiment 3. Include units in your answer.

The breakdown of hydrogen peroxide with iodide ions as a catalyst is the basis of the demonstration ‘Elephant’s Toothpaste’. The presence of a detergent results in a rapid eruption of foam as the oxygen gas is released.

Describe the test and the positive result that confirms the gas produced is oxygen.

The foam produced often has a slight yellow / brown colour.

Explain what causes this colour, which is not caused by the detergent.

The effect of temperature on the rate of the decomposition of hydrogen peroxide without a catalyst was also investigated. A graph of ln k against 1/temperature (1/ T) was plotted.

Determine the gradient of the graph. Include units in your answer. You must show your working on the graph.

Calculate the activation energy, E_a, of the reaction, in kJ mol^–1, using your answer to (e)(i) and the Arrhenius equation shown.

[Gas constant (R) = 8.31 J mol^–1K^–1]

* 4 Discuss the role society, and chemists in particular, can play in order to contribute to a more sustainable use of polymers.

Your answer should consider

• the different ways of dealing with waste polymers

• how chemists can limit the problems caused by the disposal of polymers.

This question is about cyclic compounds.

The energy density of a fuel is defined as the energy released per dm³ of the liquid fuel burned.

A sample of cyclopentane with a mass of 30.0 g releases 1.41 MJ of energy.

Calculate the energy density of cyclopentane. Include units in your answer.

[Density of cyclopentane = 0.751 g cm^–3]

State the condition needed to initiate the reaction.

Draw the structure of the organic product of an alternative termination step.

Explain why the solvent ethanol is treated with anhydrous sodium sulfate before use in this reaction.

Give the name of the reaction shown in the equation.

This question is about nuclear magnetic resonance (NMR) spectroscopy.

Which part of the electromagnetic spectrum is used in NMR?

Explain why tetramethylsilane, TMS, is used in NMR spectroscopy.

A secondary amine, Q, has the molecular formula C₆H₁₅N. The low resolution¹H NMR spectrum of Q has three peaks.

State what is meant by the term ‘secondary amine’.

Deduce the structure of Q.

Two cyclic alcohols have the structures shown.

Show that the¹³C NMR spectra of these compounds can be used to distinguish between the two alcohols, labelling the diagrams to justify your answer.

This question is about polymers, an example of which is neoprene, a synthetic rubber material. It is formed by the polymerisation of chloroprene.

What is the IUPAC name of chloroprene?

Calculate the volume, in cm³, occupied by 10.0 g of chloroprene in the gaseous phase, at 80.0C and 205 kPa. Give your answer to an appropriate number of significant figures.

[Gas constant (R) = 8.31 J mol^–1K^–1]

Chloroprene is formed by first adding chlorine, Cl₂, to Compound A and then removing hydrogen chloride from the product of this reaction.

Explain how chlorine, Cl₂, can act as an electrophile in Step 1 even though a chlorine molecule is symmetrical. You may find it helpful to include a diagram.

Draw the mechanism for Step 1. Include curly arrows, and any relevant lone pairs and dipoles.

Chloroprene polymerises to form neoprene as shown.

Give the name of the type of reaction that occurs when chloroprene polymerises.

Flexible and water‑resistant materials can be made by combining neoprene with polyester fabric.

A polyester may be made by the reaction of benzene‑1,4‑dicarboxylic acid with ethane‑1,2‑diol.

Explain why ethane‑1,2‑diol is soluble in water. A detailed description of the forces involved is not required.

The molar mass of a polyester is 8400 g mol^–1.

Calculate the number of polymer molecules in 4.25 mg of this polyester.

[Avogadro constant (L) = 6.0210²³mol^–1]

A student spilled a small amount of 0.40 mol dm^–3 sodium hydroxide solution onto a polyester laboratory coat. A hole formed in the laboratory coat as the result of a chemical reaction.

What type of reaction occurred?

Both amino acids contain a chiral carbon atom.

State what is meant by the term ‘chiral carbon atom’.

Draw diagrams of the two stereoisomers of alanine, showing their three‑dimensional shape.

Draw the skeletal formulae of the two dipeptides that could form when serine and alanine react.

Sodium ethoxide, C₂H₅ONa, needed in Step 1, is formed by the reaction of sodium with ethanol.

Write the equation for this reaction. State symbols are not required.

Name the two functional groups present in Compound Y.

Give the reagent needed and conditions required for Step 3.

Calculate the mass of Compound X required to make 15.0 g of alanine, assuming the overall yield of the synthesis is 55 %.