Chemistry — A-Level

Halogenoalkanes — Multiple-Choice Questions (Cambridge International A-Level Chemistry): Exam Questions

30 questions · 30 marks · ≈ 30 min

Guided practice

11 markeasy

X and Y are the reagents required to convert 1-bromopropane into butanoic acid.

Reaction scheme showing the two-step conversion of 1-bromopropane to butanoic acid via a nitrile intermediate, with reagent boxes X and Y to complete

Which row correctly identifies X and Y?

	X	Y
A	NH₃	HCl (aq)
B	KCN in C₂H₅OH	NaOH (aq)
C	KCN in C₂H₅OH	HCl (aq)
D	HCN	NaOH (aq)

Choose your answer

21 markeasy

Which reaction occurs when ethane and chlorine are mixed in diffused sunlight?

Choose your answer

A free-radical substitution with hydrogen given off.

A free-radical substitution with hydrogen chloride given off.

A free-radical substitution with no gas given off.

A nucleophilic substitution with hydrogen chloride given off.

31 markeasy

Chlorofluoroalkanes, CFCs, can be used as refrigerants, aerosol propellants and fire extinguishers.

CFCs such as CCl₃F and CCl₂F₂ are more stable than chloroalkanes such as CCl₄.

What is the reason for their greater stability?

Choose your answer

Fluorine has a higher first ionisation energy than chlorine.

Fluorine radicals are more stable than chlorine radicals.

The C–F bond energy is larger than the C–Cl bond energy.

The C–F bond is more polar than the C–Cl bond.

41 markeasy

Light initiates the following reaction.

alkane + chlorine $\rightarrow$ chloroalkane + hydrogen chloride

What happens to the chlorine molecule during this photochemical reaction?

Choose your answer

Heterolytic fission to give an electrophile.

Heterolytic fission to give a free radical.

Homolytic fission to give an electrophile.

Homolytic fission to give a free radical.

51 markeasy

High-energy irradiation in the stratosphere produces radicals from halogenoalkanes.

Which radical could result from this irradiation of CHFClCF₂Cl?

Choose your answer

CHFClC•FCl

•CHClCF₂Cl

•CHFCF₂Cl

•CFClCF₂Cl

61 markeasy

Which reaction is an example of nucleophilic substitution?

Choose your answer

CH₃CH₂Br + KOH (ethanolic) $\rightarrow$ CH₂=CH₂ + KBr + H₂O

CH₂=CH₂ + HBr $\rightarrow$ CH₃CH₂Br

C₃H₇Br + H₂O $\rightarrow$ C₃H₇OH + HBr

C₂H₆ + Br₂ $\rightarrow$ C₂H₅Br + HBr

71 markeasy

Bromomethane, CH₃Br, is used as a fumigant to destroy insect pests in grain that is to be stored. It can be made by reacting methanol with hydrogen bromide.

CH₃OH + HBr $\rightarrow$ CH₃Br + H₂O

What type of reaction is this?

Choose your answer

Condensation

Electrophilic substitution

Free radical substitution

Nucleophilic substitution

81 markeasy

Dichlorodifluoromethane, CCl₂F₂, has been used in aerosol propellants and as a refrigerant.

Which statement helps to explain why dichlorodifluoromethane is chemically inert?

Choose your answer

Fluorine compounds are non-flammable.

Fluorine is highly electronegative.

The carbon-fluorine bond energy is large.

The carbon-fluorine bond has a low polarity.

91 markeasy

The reaction of chlorine with methane is carried out in the presence of ultraviolet light.

What is the function of the ultraviolet light?

Choose your answer

To break the C–H bonds in methane.

To break up the chlorine molecules into ions.

To break the Cl–Cl bond homolytically to form chlorine radicals.

To heat up the mixture.

101 markmedium

Four drops of 1-chlorobutane, 1-bromobutane and 1-iodobutane were put separately into three test-tubes containing 1.0 cm³ of aqueous silver nitrate at 60 °C.

A hydrolysis reaction occurred.

R represents the butane chain C₄H_9– and X the halogen atom.

H₂O (l) + R–X (l) + Ag⁺ (aq) $\rightarrow$ R–OH (aq) + AgX (s) + H⁺ (aq)

The rate of formation of cloudiness in the tubes was in the order RCl < RBr < RI

Which statement explains this order of reactivity?

Choose your answer

The bond energy of R–X decreases from RCl to RI.

The ionisation energy of the halogen decreases from Cl to I.

The R–X bond polarity decreases from RCl to RI.

The solubility of AgX (s) decreases from AgCl to AgI.

111 markmedium

What is involved in the mechanism of the reaction between aqueous sodium hydroxide and 1-bromobutane?

Choose your answer

Attack by a nucleophile on a carbon atom with a partial positive charge.

Heterolytic bond fission and attack by a nucleophile on a carbocation.

Homolytic bond fission and attack by an electrophile on a carbanion.

Homolytic bond fission and combination of two radicals.

121 markmedium

A reaction between chlorine and propane in the presence of ultraviolet light produces two isomeric monochloropropanes, C₃H₇Cl.

Which row identifies the type of bond fission in the initiation step and the expected ratio of 1-chloropropane to 2-chloropropane produced?

	Type of bond fission in initiation step	Expected ratio of 1-chloropropane to 2-chloropropane produced
A	Heterolytic	1:1
B	Heterolytic	3:1
C	Homolytic	1:1
D	Homolytic	3:1

Choose your answer

131 markmedium

Bromine and propene undergo an addition reaction.

Which statement about the product is correct?

Choose your answer

It exists in cis-trans isomers.

It is more volatile than propene

It possesses a chiral centre.

It possesses hydrogen bonding.

141 markmedium

Which compound undergoes an S_N1 substitution reaction?

Choose your answer

CH₃CH₂CH₂Br

(CH₃)₃CCH₂I

CH₂=CHCl

1-chloro-1-methylcyclohexane

151 markmedium

CCl₂FCClF₂ is converted to a fluorocarbon by the following route:

CCl₂FCClF₂ $\overset{\text{step 1}}{\rightarrow}$ CCl₃CF₃ $\overset{\text{step 2}}{\rightarrow}$ CCl₂FCF₃

What type of reaction is step 2?

Choose your answer

Electrophilic substitution

Free-radical substitution

Isomerisation

Nucleophilic substitution

161 markmedium

The presence of a halogen in an organic compound may be detected by warming the organic compound with aqueous ethanolic silver nitrate.

Which compound would be the quickest to produce a precipitate?

Choose your answer

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171 markmedium

In the hydrolysis of bromoethane by aqueous sodium hydroxide, which row correctly describes the attacking group and the leaving group?

	Attacking group	Leaving group
A	Electrophile	Electrophile
B	Electrophile	Nucleophile
C	Nucleophile	Electrophile
D	Nucleophile	Nucleophile

Choose your answer

181 markmedium

Which reaction will give the highest yield of 2-chloropropane as the only organic product?

Choose your answer

Propan-2-ol with dilute NaCl (aq)

Propan-2-ol with SOCl₂

Propane gas with chlorine gas in the presence of ultraviolet light

Propene with HCl (g)

191 markmedium

Aqueous sodium hydroxide reacts with 1-bromopropane to give propan-1-ol.

Which statement correctly describes the mechanism of this reaction?

Choose your answer

By a curly arrow from a lone pair on the OH^– ion to the C^δ+ atom of 1-bromopropane.

By a curly arrow from the C^δ+ atom of 1-bromopropane to the OH^– ion.

By a curly arrow from the C–Br bond to the C atom.

By the homolytic fission of the C–Br bond.

201 markmedium

The table shows the time taken for a silver halide precipitate to appear when halogenoalkanes react with aqueous ethanolic silver nitrate at 50 ^oC.

halogenoalkane	time for precipitate / s
1-chlorobutane	>300
1-bromobutane	120
1-iodobutane	15

Which statement explains the differences in the times taken for the precipitate to appear?

Choose your answer

The C–I bond is the strongest of the carbon-halogen bonds

The C–X bond strength decreases from C–Cl to C–I

The rate of reaction depends on the oxidising power of the halogens

The rate of reaction is determined by the polarity of the C–X bond

211 markmedium

Bromoethane reacts with ammonia to form ethylamine.

Which set of conditions is required to maximise the yield of ethylamine and minimise further substitution products?

Choose your answer

Heat ammonia with excess bromoethane in a sealed tube.

Heat bromoethane with excess ammonia in a sealed tube.

Heat bromoethane with aqueous ammonia under reflux.

Heat bromoethane with excess ethanolic ammonia in a sealed tube.

221 markmedium

Consider the two-step synthesis:

ethane $\overset{\mathrm{step}1}{\rightarrow}$ bromoethane $\overset{\mathrm{step}2}{\rightarrow}$ ethylamine

	step 1 reagents	step 2 reagents
A	Br₂, UV light	NH₃, ethanol, heat under pressure
B	HBr, room temperature	NH₃, aqueous, reflux
C	Br₂, UV light	KCN, ethanol, reflux
D	PBr₃, reflux	HNO₃, room temperature

Which row shows the correct reagents and conditions?

Choose your answer

231 markhard

When an isomer Y of molecular formula C₄H₉Br undergoes hydrolysis in aqueous sodium hydroxide to form an alcohol C₄H₉OH, the rate of reaction is found to be independent of the concentration of OH^– ions present.

Which is the most likely molecular structure of Y?

Choose your answer

(CH₃)₂CHCH₂Br

CH₃CH₂CH₂CH₂Br

(CH₃)₃CBr

CH₃CH₂CHBrCH₃

241 markhard

A tertiary bromoalkane, indicated here by C–Br, reacts with aqueous NaOH. The mechanism has the reaction pathway below.

Double-bump reaction pathway diagram for SN1 hydrolysis of a tertiary bromoalkane, with energy maxima as transition states and energy minimum as carbocation intermediate, points X and Y labelled

Which point in the diagram is correctly identified?

Choose your answer

251 markhard

When a solution of potassium cyanide in ethanol is heated under reflux with 1-chloropropane, what is the organic product of the reaction?

Choose your answer

1-chloropropanenitrile

Butanenitrile

Ethanenitrile

Propanenitrile

261 markhard

The compound 2-ethyl-3-methylbutanoic acid is used as a flavouring in some food.

Structural formula of 2-ethyl-3-methylbutanoic acid showing a branched carbon chain with ethyl and methyl substituents on adjacent alpha and beta carbons and a carboxylic acid group

Which compound produces 2-ethyl-3-methylbutanoic acid when heated under reflux with potassium cyanide in ethanol, followed by acid hydrolysis of the reaction product?

Choose your answer

271 markhard

When phenacyl chloride, C₆H₅COCH₂Cl, is reacted with aqueous NaOH, the substitution reaction follows an S_N2 mechanism.

Which structure represents the transition state for this reaction?

Choose your answer

281 markhard

Coniine is the major constituent of the poison 'oil of hemlock'.

Structure of coniine showing a six-membered piperidine ring with a nitrogen atom and a propyl substituent

Coniine can be synthesised by reacting ammonia with a dibromo compound, X, C₈H₁₆Br₂ .

NH₃ + X $\rightarrow$ coniine + 2HBr

What is the name of compound X?

Choose your answer

1,1-dibromo-2-propylcyclopentane

1,2-dibromo-2-propylcyclopentane

1,4-dibromooctane

1,5-dibromooctane

291 markhard

A reaction pathway diagram is shown.

Double-bump reaction pathway diagram with two transition state energy maxima and one intermediate energy minimum, characteristic of a two-step mechanism

Which reaction does not have such a profile?

Choose your answer

(CH₃)₃CBr + NaOH → (CH₃)₃COH + NaBr

C₂H₅Br + NaOH → C₂H₅OH + NaBr

CH₃CHO + HCN $\overset{\text{NaCN}}{\rightarrow}$ CH₃CH(OH)CN

cyclohex-1-ene + Br₂ → 1,2-dibromocyclohexane

301 markhard

Which molecule has no permanent dipole?

Choose your answer

CCl₂F₂

CHCl₃

C₂Cl₄

C₂H₅Cl

NH₃

HCl (aq)

KCN in C₂H₅OH

NaOH (aq)

KCN in C₂H₅OH

HCl (aq)

HCN

NaOH (aq)

Type of bond fission in initiation step

Expected ratio of 1-chloropropane to 2-chloropropane produced

Heterolytic

1:1

Heterolytic

3:1

Homolytic

1:1

Homolytic

3:1

Attacking group

Leaving group

Electrophile

Nucleophile

Electrophile

Nucleophile

halogenoalkane

time for precipitate / s

1-chlorobutane

>300

1-bromobutane

120

1-iodobutane

step 1 reagents

step 2 reagents

Br₂, UV light

NH₃, ethanol, heat under pressure

HBr, room temperature

NH₃, aqueous, reflux

Br₂, UV light

KCN, ethanol, reflux

PBr₃, reflux

HNO₃, room temperature