Edexcel IAL Chemistry AS Topic 10 Halogenoalkanes, alcohols and spectra

Pearson Edexcel IAL Chemistry syllabusChemistry YCH11First assessment 2019

Identify structures and reaction class first, then supply precise reagents, conditions, curly arrows or diagnostic spectral peaks required by the pathway or evidence.

Exam points

Draw nucleophilic substitution and elimination mechanisms with correct curly arrows.
Plan halogenoalkane or alcohol conversions using named reagents, conditions and products.
Interpret hydrolysis experiments, infrared absorptions and mass-spectral fragments.

[Maximum number: 10]

This question is about two organic compounds, X and Y. Both are liquids which contain carbon, hydrogen and oxygen only.

(a)

When phosphorus(V) chloride is added to X, steamy white fumes are seen.

State what can be deduced about compound X from this observation only.

[ 1 ]

(b)

Compound X is converted into compound Y when refluxed with excess sodium dichromate(VI) in sulfuric acid.

Compound Y is a liquid that is soluble in the reaction mixture.
Draw a labelled diagram of the apparatus that could be used to separate Y from the reaction mixture.

[ 3 ]

(c)

The infrared spectrum of Y is shown.

The table shows some infrared absorption data.

Explain how this spectrum shows that Y contains a carboxylic acid functional group, quoting data from the table.

[ 2 ]

(d)

The mass spectrum of Y is shown.

[ 2 ]

(i)

Show that the mass spectrum is consistent with Y having the molecular formula $\mathrm{C}_{3} \mathrm{H}_{4} \mathrm{O}_{3}$ .

[ 1 ]

(ii)

Suggest the structure of the ion causing the peak at m / z=43 in the mass spectrum of Y.

[ 1 ]

(e)

Compound X contains one type of functional group.

Compound Y contains two different functional groups.
Use the information in the question to deduce the structures of X and Y.

Compound X

Compound Y

[ 2 ]

Which of these alcohols will produce a carboxylic acid when heated under reflux with acidified potassium dichromate(VI)?

□ A P only
□ B P and Q only
□ C P, Q and R only
□ D P, Q, R and S

[Maximum number: 3]

Two reactions of cyclohexanol are shown.

(a)

What is the reagent for Reaction 1?

acidified potassium manganate(VII)

aqueous bromine

concentrated phosphoric(V) acid

phosphorus(V) chloride

[ 1 ]

(b)

The reagent for Reaction 2 is acidified potassium dichromate(VI).

Which equation best represents this reaction?
□

A $\mathrm{C}_{6} \mathrm{H}_{11} \mathrm{OH} \rightarrow \mathrm{C}_{6} \mathrm{H}_{10} \mathrm{O}+\mathrm{H}_{2}$

□

B $\mathrm{C}_{6} \mathrm{H}_{11} \mathrm{OH} \rightarrow \mathrm{C}_{6} \mathrm{H}_{10} \mathrm{O}+2[\mathrm{H}]$

□

C $\mathrm{C}_{6} \mathrm{H}_{11} \mathrm{OH}+[\mathrm{O}] \rightarrow \mathrm{C}_{6} \mathrm{H}_{10} \mathrm{O}+\mathrm{H}_{2} \mathrm{O}$

□

D $\mathrm{C}_{6} \mathrm{H}_{11} \mathrm{OH}+\frac{1}{2} \mathrm{O}_{2} \rightarrow \mathrm{C}_{6} \mathrm{H}_{10} \mathrm{O}+\mathrm{H}_{2} \mathrm{O}$

[ 1 ]

(c)

Cyclohexanol and cyclohexene each has a peak in their infrared spectrum which is not present for the other compound.

Which are these peaks?
□ A
□ B
□ C
□ D

(Total for Question 14 = 3 marks)

TOTAL FOR SECTION A = 20 MARKS

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

[ 1 ]

[Maximum number: 10]

Ammonia reacts with 1-chlorobutane.

(a)

State the type and mechanism of this reaction.

[ 2 ]

(b)

A student drew the first step of the mechanism for the reaction.

[ 5 ]

(i)

Identify two omissions in the student's mechanism.

[ 2 ]

(ii)

To obtain butylamine, sodium hydroxide solution is added.

Complete the next step of the mechanism to form butylamine, showing curly arrows, relevant lone pairs and the reaction products.
(3)

[ 3 ]

(c)

The reactions of ammonia and of hydroxide ions with halogenoalkanes are similar. Compare the rate of reaction of ammonia with 1-chlorobutane and with 2-bromo-2-methylpropane. Justify your answer.

[ 3 ]

[Maximum number: 14]

Cyclohexene, $\mathrm{C}_{6} \mathrm{H}_{10}$ , was prepared by dehydrating cyclohexanol, $\mathrm{C}_{6} \mathrm{H}_{11} \mathrm{OH}$ , using concentrated phosphoric (V) acid, $\mathrm{H}_{3} \mathrm{PO}_{4}$ .

\mathrm{C}_{6} \mathrm{H}_{11} \mathrm{OH}(\mathrm{l}) \rightarrow \mathrm{C}_{6} \mathrm{H}_{10}(\mathrm{l})+\mathrm{H}_{2} \mathrm{O}(\mathrm{l})

Procedure

Step 1 Approximately $12 \mathrm{~cm}^{3}$ of cyclohexanol was measured into a small flask.
Step $25 \mathrm{~cm}^{3}$ of concentrated phosphoric(V) acid was added slowly to the flask with cooling and swirling.

Step 3 Some anti-bumping granules were added to the mixture.
Step 4 The flask was set up for distillation, using the apparatus shown, and the distillate was collected between $80^{\circ} \mathrm{C}$ and $90^{\circ} \mathrm{C}$ .

Step 5 The distillate was transferred to a separating funnel and washed with an aqueous solution of sodium carbonate.

Step 6 The crude organic product was separated from the mixture, placed in a clean separating funnel and washed with deionised water.

Step 7 The organic layer was separated and dried using a suitable drying agent.
Step 8 The dried organic layer was distilled, over a narrow range of temperature, to give pure cyclohexene.

VIIIV SIHI NI JIIYM IONOO	VJYV SIAL NI IIIYM ION OC	VIIV SIHI NI JIIIM ION OC

(a)

Explain why adding phosphoric(V) acid slowly, with cooling and swirling,

[ 2 ]

(b)

Explain why, in Step 4, the distillate is collected in a temperature range of $80^{\circ} \mathrm{C}$ to $90^{\circ} \mathrm{C}$ .
(2)

[ 2 ]

(c)

State what is removed by washing the mixture with
sodium carbonate solution in Step 5.
Include an ionic equation for the reaction.
State symbols are not required.

[ 2 ]

(d)

After the washing in Step 5, the separating funnel contains two layers.

Draw a diagram of the separating funnel, labelling its contents.
(2)

[ 2 ]

(e)

Suggest what might be removed by washing the product with deionised water in Step 6.

[ 1 ]

(f)

Identify from the list shown one substance that could be used as a drying agent in Step 7 of this procedure. Justify your choice.

[ 2 ]

(g)

Chemical tests may be used to show whether or not reactants and products are present during the course of the procedure.

[ 3 ]

(i)

State a chemical test and the expected observation for an -OH group.

[ 2 ]

(ii)

State whether or not the test in (g)(ii) could be used on the organic product to show if cyclohexanol remains when Step 5 is complete.
Justify your answer.
(1)

[ 1 ]

[Maximum number: 9]

This question is about some halogenoalkanes.

(a)

Give the classification of each halogenoalkane shown in the table as primary, secondary or tertiary.

[ 1 ]

(b)

Samples of 1-iodobutane and 2-chloro-2-methylpropane were hydrolysed using aqueous silver nitrate in ethanol.

Explain whether or not it is possible to predict the relative rate of hydrolysis of these two compounds.

[ 3 ]

(c)

Butylamine is formed when 1-bromobutane reacts with excess concentrated alcoholic ammonia.

\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{Br}+2 \mathrm{NH}_{3} \rightarrow \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{NH}_{2}+\mathrm{NH}_{4} \mathrm{Br}

[ 5 ]

(i)

Give a reason why this reaction should be carried out by heating the reactants in a sealed tube rather than heating under reflux.

[ 1 ]

(ii)

Complete the mechanism for this reaction by adding curly arrows, and any relevant lone pairs and dipoles.

[ 4 ]

[Maximum number: 2]

Some diesel cars contain an extra catalytic converter for the reduction of nitrogen oxides $\left(\mathrm{NO}_{\mathrm{x}}\right)$ in exhaust gases.
A solution of urea is used for this process.

urea

(a)

An infrared spectrum of urea is shown.

Refer to your Data Booklet.

$stretching of the \(\mathrm{N$

stretching of the \(\mathrm{N

[ 2 ]

(i)

Draw a circle around an absorption in the spectrum that could be due to the

[ 1 ]

(ii)

Identify the bond responsible for the absorption at $1683 \mathrm{~cm}^{-1}$ .

ption in

[ 1 ]

Exam points

Question 2

Question 2(b)

Question 2(c)

Question 2(d)

Question 2(e)

Question 2(e)(i)

Question 2(e)(ii)

Question 2(f)

Question 13

Question 14

Question 14(a)

Question 14(b)

Question 14(c)

Question 20

Question 20(a)

Question 20(b)

Question 20(b)(i)

Question 20(b)(ii)

Question 20(c)

Question 3

Question 3(b)

Question 3(d)

Question 3(e)(i)

Question 3(e)(ii)

Question 3(e)(iii)

Question 3(f)

Question 3(g)

Question 3(g)(ii)

Question 3(g)(iii)

Question 17

Question 17(a)

Question 17(b)

Question 17(c)

Question 17(c)(i)

Question 17(c)(ii)

Question 24

Question 24(d)

Question 24(d)(i)

Question 24(d)(ii)