ASChemistryCambridge (CIE)Exam Questions15. Halogen CompoundsHalogenoalkanes

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

Exam code: 9701

3 hours42 questions

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Halogenoalkanes

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1
1 mark

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

3-3-cie-ial-chemistry-diagram-q1easy

What are the correct identities of X and Y?

 

X

Y

A

B

C

D

NH3

KCN in C2H5OH

KCN in C2H5OH

HCN

HCl (aq)

NaOH (aq)

HCl (aq)

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 rightwards arrow chloroalkane + hydrogen chloride

    What happens to chlorine in this photochemical reaction?

    • Heterolytic fission to give an electrophile.

    • Homolytic fission to give an electrophile.

    • Heterolytic fission to give a free radical.

    • 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 rightwards arrow CH2=CH2 + HBr

    • 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?

    • The carbon-fluorine bond energy is large.

    • The carbon-fluorine bond has a low polarity.

    • Fluorine is highly electronegative.

    • Fluorine compounds are non-flammable.

    Choose your answer

    9
    1 mark

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

    What is the function of the light?

    • To break the C–H bonds in methane.

    • To break up the chlorine molecules into radicals.

    • To break up the chlorine molecules into ions.

    • 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) rightwards arrow R–OH (aq) + AgX (s) + H+ (aq)

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

    Why is this?

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

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

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

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

    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 attack by a nucleophile on a carbocation.

    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 is a property of the product?

      • 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

      • 3-3-m-6

      • CH2=CHCl

      Choose your answer

      6
      1 mark

      Under the Montreal Protocol, the manufacture of chlorofluorocarbons has been phased out, and they are being replaced by fluorocarbons.

      One chlorofluorocarbon which was widely used as a solvent is CCl2FCClF2. Large stocks of it remain. One process to use up these stocks is to convert it into the fluorocarbon CH2FCF3 by the following route.

      u42czm3Q_3-3-m-7

      What type of reaction is step 2?

      • Electrophilic substitution

      • Free radical reduction

      • 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 silver nitrate.

      Which compound would be the quickest to produce a precipitate?

      • 3-3-m-8a
      • 3-3-m-8b
      • 3-3-m-8c
      • 3-3-m-8d

      Choose your answer

      8
      1 mark

      In the hydrolysis of bromoethane by aqueous sodium hydroxide, what is the nature of the attacking group and of the leaving group?

       

      Attacking group

      Leaving group

      A

      B

      C

      D

      Electrophile

      Electrophile

      Nucleophile

      Nucleophile

      Electrophile

      Nucleophile

      Electrophile

      Nucleophile

        Choose your answer

        9
        1 mark

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

        • Propane gas with chlorine gas in the presence of ultraviolet light

        • Propan-2-ol with dilute NaCl (aq)

        • Propan-2-ol with SOCl2

        • Propene with dilute HCl (aq)

        Choose your answer

        10
        1 mark

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

        How should the first step in the mechanism be described?

        • 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 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 rate of reaction is determined by the polarity of the C-X bond

        • The C-X bond strength decreases from C-Cl to C-I

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

        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 bromoethane with excess ethanolic ammonia in a sealed tube.

        • Heat ammonia with excess bromoethane in a sealed tube.

        • Heat bromoethane with aqueous ammonia under reflux.

        • Heat bromoethane with ammonia gas at room temperature.

        Choose your answer

        13
        1 mark

        Consider the two-step synthesis:

        ethane rightwards arrow with step space 1 on top bromoethane rightwards arrow with step space 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 set of reagents and conditions correctly completes the sequence?

          Choose your answer

          1
          1 mark

          When an isomer Y of molecular formula C4H9Br undergoes hydrolysis in aqueous alkali to form  an alcohol C4H9OH, the rate of reaction is found to be unaffected by changes in the concentration of OH– ions present.

          Which is the most likely molecular structure of Y?

          • CH3CH2CH2CH2Br

          • CH3CH2CHBrCH3

          • (CH3)2CHCH2Br

          • (CH3)3CBr

          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?

          • 3-3-h-4a
          • 3-3-h-4b
          • 3-3-h-4c
          • 3-3-h-4e

          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 called?

          • Butanenitrile

          • 1-chloropropanenitrile

          • Ethanenitrile

          • Propanenitrile

          Choose your answer

          4
          1 mark

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

          3-3-h-6

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

          • 3-3-h-6a
          • 3-3-h-6b
          • 3-3-h-6c
          • 3-3-h-6d

          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 a species formed during the reaction?

          • 3-3-h-7a
          • 3-3-h-7b
          • 3-3-h-7c
          • 3-3-h-7d

          Choose your answer

          6
          1 mark

          Coniine is the major constituent of the poison ‘oil of hemlock’.

          3-3-h-8

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

                                         NH3 + C8H16Br2 rightwards arrow coniine + 2HBr

                                                           X

          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.

          3-3-h-9

          Which reaction does not have such a profile?

          • CH3CHO + HCN  rightwards arrow with NaCN on top  CH3CH(OH)CN

          • C2H5Br + NaOH rightwards arrow C2H5OH + NaBr

          • (CH3)3CBr + NaOH rightwards arrow (CH3)3COH + NaBr

          • 3-3-h-9a

          Choose your answer

          8
          1 mark

          Which of the following molecules will have no permanent dipole?

          • CCl2F2

          • CHCl3

          • C2Cl4

          • C2H5Cl

          Choose your answer