ASChemistryCambridge (CIE)Exam Questions15. Halogen CompoundsHalogenoalkanes

Halogenoalkanes (Cambridge (CIE) AS Chemistry): Exam Questions

Exam code: 9701

3 hours42 questions

Select a download format for Halogenoalkanes

Scroll for more

Select an answer set to view for
Halogenoalkanes

Easy
Medium
Hard
1
1 mark

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

    2
    1 mark

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

    • 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.

    Choose your answer

    3
    1 mark

    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?

    • 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.

    Choose your answer

    4
    1 mark

    Light initiates the following reaction.

    alkane + chlorine \rightarrow chloroalkane + hydrogen chloride

    What happens to the chlorine molecule during this photochemical reaction?

    • 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.

    Choose your answer

    5
    1 mark

    High-energy irradiation in the stratosphere produces radicals from chlorofluoroalkanes, commonly known as CFCs.

    Which radical could result from this irradiation of CHFClCF2Cl?

    • CHFClC•FCl

    • •CHClCF2Cl

    • •CHFCF2Cl

    • •CFClCF2Cl

    Choose your answer

    6
    1 mark

    Which reaction is an example of nucleophilic substitution?

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

    • CH2=CH2 + HBr rightwards arrow CH3CH2Br

    • C3H7Br + H2O rightwards arrow C3H7OH + HBr

    • C2H6 + Br2 rightwards arrow C2H5Br + HBr

    Choose your answer

    7
    1 mark

    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  rightwards arrow  CH3Br  + H2O

    What type of reaction is this?

    • Condensation

    • Electrophilic substitution

    • Free radical substitution

    • Nucleophilic substitution

    Choose your answer

    8
    1 mark

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

    Which statement helps to explain why dichlorodifluoromethane is chemically inert?

    • Fluorine compounds are non-flammable.

    • Fluorine is highly electronegative.

    • The carbon-fluorine bond energy is large.

    • The carbon-fluorine bond has a low polarity.

    Choose your answer

    9
    1 mark

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

    What is the function of the ultraviolet light?

    • 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.

    Choose your answer

    1
    1 mark

    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 C4H9– 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?

    • 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.

    Choose your answer

    2
    1 mark

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

    • 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.

    Choose your answer

    3
    1 mark

    A reaction between chlorine and propane in ultraviolet light produces two isomeric monochloropropanes, C3H7Cl, as products.

    Which information about this reaction is correct?

    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

      4
      1 mark

      Bromine and propene undergo an addition reaction.

      Which statement about the product is correct?

      • It exists in cis-trans isomers.

      • It is more volatile than propene

      • It possesses a chiral centre.

      • It possesses hydrogen bonding.

      Choose your answer

      5
      1 mark

      Which compound undergoes an SN1 substitution reaction?

      • CH3CH2CH2Br

      • (CH3)3CCH2I

      • CH2=CHCl

      • 1-chloro-1-methylcyclohexane

      Choose your answer

      6
      1 mark

      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?

      • Electrophilic substitution

      • Free-radical substitution

      • Isomerisation

      • Nucleophilic substitution

      Choose your answer

      7
      1 mark

      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?

      • Skeletal formula of 1,3-dichloro-2-(chloromethyl)propane
      • Skeletal formula of 1-chloro-3-fluoro-2-(fluoromethyl)propane
      • Skeletal formula of 1-fluoro-2-(fluoromethyl)-3-iodopropane
      • Skeletal formula of 1-bromo-2-(chloromethyl)-3-fluoropropane

      Choose your answer

      8
      1 mark

      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

        9
        1 mark

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

        • 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 (aq)

        Choose your answer

        10
        1 mark

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

        Which statement correctly describes the mechanism of this reaction?

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

        • By a curly arrow from the Cδ+ 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.

        Choose your answer

        11
        1 mark

        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?

        • 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

        Choose your answer

        12
        1 mark

        Bromoethane reacts with ammonia to form ethylamine.

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

        • 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.

        Choose your answer

        13
        1 mark

        Consider the two-step synthesis:

        ethane rightwards arrow with step 1 on top bromoethane rightwards arrow with step 2 on top 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

          1
          1 mark

          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?

          • (CH3)2CHCH2Br

          • CH3CH2CH2CH2Br

          • (CH3)3CBr

          • CH3CH2CHBrCH3

          Choose your answer

          2
          1 mark

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

          3-3-cie-ial-chemistry-diagram-q4hard

          Which point in the diagram is correctly identified?

          • Double-bump SN1 energy profile with Y incorrectly placed at an energy maximum rather than the carbocation intermediate energy minimum
          • Double-bump SN1 energy profile with X incorrectly placed at the carbocation intermediate energy minimum rather than the first transition state maximum
          • Double-bump SN1 energy profile with X correctly identifying the first transition state energy maximum and Y correctly identifying the carbocation intermediate energy minimum
          • Double-bump SN1 energy profile with both X and Y incorrectly identified on the diagram

          Choose your answer

          3
          1 mark

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

          • 1-chloropropanenitrile

          • Butanenitrile

          • Ethanenitrile

          • Propanenitrile

          Choose your answer

          4
          1 mark

          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?

          • Structural formula of a 6-carbon halogenoalkane with incorrect connectivity that would not yield 2-ethyl-3-methylbutanoic acid on CN substitution and hydrolysis
          • Structural formula of a 6-carbon branched bromoalkane with the correct carbon skeleton to give 2-ethyl-3-methylbutanoic acid on CN substitution and acid hydrolysis
          • Structural formula of a 6-carbon halogenoalkane with a different branching pattern that would not give 2-ethyl-3-methylbutanoic acid
          • Structural formula of a 6-carbon halogenoalkane with a different carbon framework that would not produce the required branching in the target carboxylic acid

          Choose your answer

          5
          1 mark

          When phenacyl chloride, C6H5COCH2Cl, is reacted with aqueous NaOH, the substitution reaction follows an SN2 mechanism.

          Which structure represents the transition state for this reaction?

          • Incorrect structure that does not represent the SN2 transition state for phenacyl chloride reacting with NaOH
          • Incorrect intermediate structure that does not arise in the SN2 mechanism of phenacyl chloride with NaOH
          • Pentacoordinate SN2 transition state for phenacyl chloride with OH⁻, showing the central carbon bonded to both incoming OH and departing Cl with partial bonds
          • Incorrect species that does not correspond to any intermediate or transition state in the SN2 reaction of phenacyl chloride with NaOH

          Choose your answer

          6
          1 mark

          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?

          • 1,1-dibromo-2-propylcyclopentane

          • 1,2-dibromo-2-propylcyclopentane

          • 1,4-dibromooctane

          • 1,5-dibromooctane

          Choose your answer

          7
          1 mark

          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?

          • (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

          Choose your answer

          8
          1 mark

          Which molecule has no permanent dipole?

          • CCl2F2

          • CHCl3

          • C2Cl4

          • C2H5Cl

          Choose your answer