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OCR AS Targeted Questions for Chains and Rings

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					                            OCR AS : Targeted Questions for Chains and Rings

Contents

1. Basic concepts – nomenclature, formula (general, structural, displayed and skeletal) ,
   homologous series, functional group, cis-trans isomerism and percentage yield

2. Hydrocarbons as fuels [ ALKANES] – their source as a limited resource, fractional distillation,
   cracking, reforming and isomerisation. Uses and combustion of fuels

3. Unsaturated hydrocarbons [ALKANES] – van der Waals intermoleuclar forces, bromination and
   chlorination of methane (via homolytic fission leading to attack by free radicals…. initiation –
   propagation-termination)

4. Saturated hydrocarbons [ALKENES] – bonding and shape of ethene, electrophilic addition
   reactions e.g. with bromine, addition polymerisation, problems related to the non-
   biodegradeable nature of plastics.

5. ALCOHOLS – hydrogen bonding intermolecular forces, preparation of ethanol by fermentation
   and hydration of ethene, primary-secondary and tertiary alcohols, oxidation of 10 and 20
   alcohols, use of alcohol as supplement / replacement for hydrocarbon fuels.
   IR spectrum of C-O, O-H, and C=O.

6. HALOGENOALKANES – typical nucleophilic substitution reactions (mechanism showing
   nucleophile as an electron pair donor), relative rates of substitution of C-F, C-Cl, C-Br and C-I,
   elimination of H-X from halogenoalkane using ethanolic alkali, uses of (poly)halogenoalkanes,
   environmental damage to ozone layer caused by CFC’s.


Basic Concepts : EXAMPLE

(a)   Four members of the homologous series of alkenes are ethene, propene, but-1-ene and
            pent-1-ene.

            (i)     Give one structural feature of the compounds that makes them members of the
                    homologous series of alkenes.
                                                                                                                                                     (1)

            (ii)    State the trend in the boiling points from ethene to pent-1-ene.

                    ........................................................................................................................   (1)

            (iii)   Give the name and draw the graphical formula of an alkene that is an isomer of
                    but-1-ene and that has a different carbon skeleton.

                    Name ................................................................................................................

                    Graphical formula


                                                                                                                                                     (2)

                                                                                                                                                      1
Q1) Which one of the following is the correct name for?

      A     2-bromo-3-methylpent-2-ene

      B     2-bromo-3-ethylbut-2-ene

      C     3-bromo-2-ethylbut-2-ene

      D     4-bromo-3-methylpent-3-ene



Q2) The correct systematic name for is

      A     2,3-diethylbut-2-ene

      B     2-ethyl-3-methylpent-2-ene

      C     4-ethyl-3-methylpent-3-ene

      D     3,4-dimethylhex-3-ene




Q3) (a)     (i)     Name the alkene CH3CH2CH=CH2 .................................................................

            (ii)    Explain why CH3CH2CH=CH2 does not show geometrical isomerism.

                    ...........................................................................................................................

                    ...........................................................................................................................

            (iii)   Draw an isomer of CH3CH2CH=CH2 which does show geometrical isomerism.




            (iv)    Draw another isomer of CH3CH2CH=CH2 which does not show geometrical
                    isomerism.




                                                                                                                                                  (4)


                                                                                                                                                   2
Q4)
          Summarised directions for recording responses to multiple completion questions

                      A                            B                               C                                   D
             (i), (ii) and (iii)           (i) and (iii) only              (ii) and (iv) only                     (iv) alone
                    only

      Geometrical isomerism is shown by

      (i)       CH3CH2CH2CH=CH2

      (ii)      (CH3)2C = CHCH3

      (iii)     (CH3) 2CHCH = CH2

      (iv)      CH3CH2CH=CHCH3


                                                                                                                                            (Total 12 marks)

TOPIC 2 Alkanes as FUELS

Q5) (a)         The diagram below represents the industrial fractional distillation of crude oil.



                (i)     Identify fraction A.




                 (ii)   What property of the
                        fractions allows them to
                        be separated in the


                        column?....................................................................................................................
                                                                                                                                                         (2)

      (b)       A gas oil fraction from the distillation of crude oil contains hydrocarbons in the C15 to C19
                range. These hydrocarbons can be cracked by strong heating.

                (i)     Write the molecular formula for the alkane with 19 carbon atoms. ......................

                (ii)    Name the type of reaction involved in cracking. .................................................

                (iii)   Write an equation for one possible cracking reaction of the alkane C16H34 when the
                        products include ethene and propene in the molar ratio 2:1 and only one other
                        compound.

                        ..........................................................................................................................(4)


                                                                                                                                                          3
Q6)(a)     Crude oil is separated into fractions by fractional distillation. Outline how different
           fractions are obtained by this process.

           ...............................................................................................................................

           ...............................................................................................................................

           ...............................................................................................................................
                                                                                                                                                           (3)

     (b)   The table below gives details of the supply of, and demand for, some crude oil fractions.




           (i)       Use the data given above to explain why catalytic cracking of crude oil fractions is
                     commercially important.

                     ......................................................................................................................

                     ......................................................................................................................

           (ii)      Give the two main types of product obtained by catalytic cracking.

                     Type 1 ..........................................................................................................

                     Type 2 ..........................................................................................................
                                                                                                                                                           (4)

     (c)   Name a catalyst used in catalytic cracking. State the type of mechanism involved and
           outline the industrial conditions used in the process.

           Catalyst .................................................................................................................

           Type of mechanism ................................................................................................

           Conditions .............................................................................................................

           ...............................................................................................................................
                                                                                                                                                           (4)
                                                                                                                                              (Total 11 marks)




                                                                                                                                                            4
Q7) (a)     Butane, C4H10, is a hydrocarbon which is used as a fuel.

            (i)     Explain what is meant by the term hydrocarbon.

                    ...........................................................................................................................

            (ii)    Explain what is meant by the term fuel.

                    ...........................................................................................................................

            (iii)   Write an equation for the complete combustion of butane.

                    ...........................................................................................................................

            (iv)    Write an equation for the incomplete combustion of butane to produce carbon
                    monoxide and water.

                    ...........................................................................................................................

            (v)     Under what conditions would you expect incomplete combustion to occur?

                    ...........................................................................................................................
                                                                                                                                                       (5)

      (b)   Three different carbocations are formed by breaking C – C bonds in separate molecules of
            butane during catalytic cracking. One of these structures is shown below. Give the
            structures of the other two carbocations.

                    Structure 1                                             Structure 2                                          Structure 3




                                                                                                                                                       (2)

      (c)   Ethane can be cracked in the presence of a catalyst to produce ethene and hydrogen.

            (i)     Write an equation for this reaction.

                    ...........................................................................................................................

            (ii)    Give a suitable catalyst for this reaction.

                    ...........................................................................................................................

            (iii)   State one reason why cracking is important.

                    ...........................................................................................................................

                    ...........................................................................................................................
                                                                                                                                                       (3)
                                                                                                                                          (Total 10 marks)




                                                                                                                                                        5
TOPIC 3 Reactions of alkanes
Q8) (a) In the presence of ultraviolet light, methane and chlorine react to form a number of chlorine-
containing products, including CH2Cl2 and CHCl3

            (i)     Write an equation for the initiation step in the mechanism for this reaction.

                    .....................................................................................................................

            (ii)    Write the overall equation for the formation of CHCl3 from CH2Cl2 and Cl2

                    .....................................................................................................................

            (iii)   Write equations for the two propagation steps by which CH2Cl2 is converted into
                    CHCl3

                    Equation 1 ....................................................................................................

                    Equation 2 ....................................................................................................

            (iv)    Suggest what effect increasing the intensity of the ultraviolet light would have on
                    the rate of the reaction between methane and chlorine. Explain your answer.

                    Effect on rate ................................................................................................

                    Explanation ..................................................................................................
                                                                                                                                            (6)

Q9 (a)      Bromomethane, CH3Br, can be formed by a reaction between bromine and methane.

            The mechanism for this reaction is similar to the mechanism for the chlorination
            of methane.

            (i)     Name the mechanism for this reaction.

                    ...........………………………………………………………………………….

            (ii)    Give the name of, and state an essential condition for, the first step in the
                    mechanism for this reaction.

                    Name …………………………………………………………………………..

                    Essential condition …………………………………………………………….

            (iii)   Write an equation for a termination step in the mechanism for this reaction which
                    gives ethane as a product.




                    ...........………………………………………………………………………….


                                                                                                                                             6
            (iv)      Bromomethane can undergo further substitution. Write an overall equation for the
                      reaction between bromomethane and bromine in which dibromomethane is formed.




                      ...........………………………………………………………………………….
                                                                                                                                                      (5)

      TOPIC 4 Alkenes

Q10) There are five structural isomers of the molecular formula C5H10 which are alkenes. The
     graphical formulae of two of these isomers are given.




                                Isomer 1                                                                Isomer 2

      (a)   Draw the graphical formulae of two of the remaining alkene structural isomers.




                      Isomer 3                                                           Isomer 4
                                                                                                                                                      (2)

             (b)      Isomer 1 can be converted directly into 2-methylbutane. State the reagent(s) and
                      condition(s) required for this reaction.

                      Reagent(s) .........................................................................................................

                      Condition(s) ................................................................................................             (3)

      (c)   The mechanism for the reaction between Isomer 1 and HBr is known as electrophilic
            addition. State what is meant by the term electrophilic addition.

            .....................................................................................................................................
                                                                                                                                                      (2)

      (d)   Draw the mechanism for the electrophilic addition reaction between ethene and HBr.




                                                                                                                                                      (3)


                                                                                                                                                       7
      Q11) (a) Alkenes can be made in the laboratory from halogenoalkanes by heating them with a
            suitable reagent. By a similar method, cyclohexene can be prepared from
            bromocyclohexane.

            (i)     Suggest the name of a suitable reagent and state an essential condition, other than
                    heat, for this reaction, starting from bromocyclohexane.

                    Reagent .............................................................................................................

                    Condition ..........................................................................................................
                                                                                                                                                       (2)

            (ii)    Using graphical formulae, write an equation for this reaction.




                                                                                                                                                       (2)

            (iii)   Give the name of this type of reaction.

                    ...........................................................................................................................
                                                                                                                                                       (1)

                                                                                                                                          (Total 13 marks)


Q13) The correct name for the alkene monomer which forms the polymer shown below is

                    A      2-methyl-3-ethylpropene

      B     2-methylpent-2-ene

      C     2-methylpent-3-ene

      D     4-methylpent-2-ene




(a)   The hydrocarbon M has the structure shown



            (i)     Name hydrocarbon M.

            (ii)    Draw the repeating unit of the polymer which can be formed from M. State the
                    type of polymerisation occurring in this reaction.

                    Repeating unit



                    Type of polymerisation .....................................................................................


                                                                                                                                                        8
Topic 5 Alcohols

Q14) Which one of the following reactions does not produce ethanol?

      A     CH3CH2Br warmed with aqueous sodium hydroxide

      B     CH3COOCH3 warmed with aqueous sodium hydroxide

      C     CH3CHO vapour passed with hydrogen over hot platinum

      D     CH2=CH2 passed with steam over phosphoric acid at high pressure



Q15) Which one of the following cannot be produced by oxidation of propan-l-ol?

      A     carbon dioxide

      B     propanone

      C     propanal

      D     propanoic acid


Q16) Which one of the following does not represent an oxidation?

      A     propene  propane

      B     propan–l–ol  propanal

      C     propan–l–ol propanoic acid

      D     propanal  propanoic acid



Q17) (a)    (i)    Write an equation for the reaction of butan-2-ol with ethanoic acid, showing clearly
                   the structure of the organic product.




            (ii)   Name the type of organic compound formed in part (a)(i) and suggest a use for this
                   compound.

                   Type of compound.............................................................................................

                   Use.....................................................................................................................



                                                                                                                                              9
             (iii)     Give a homogeneous catalyst for the reaction in part (a)(i) and state the meaning of
                       the term homogeneous.

                       Catalyst..............................................................................................................

                       Meaning of homogeneous.................................................................................
                                                                                                                                                     (6)

      (b)    Write an equation for the complete combustion of butan-2-ol in an excess of oxygen.

             .....................................................................................................................................
                                                                                                                                                     (1)

      (c)    But-1-ene and other products can be made by the dehydration of butan-2-ol.

             (i)       Outline a mechanism for the dehydration of butan-2-ol into but-l-ene.




             (ii)      Explain why but-1-ene does not show geometrical isomerism.


Q18) A methyl-substituted cyclopentene A, C6H10, is converted into compound B, C6H11Br, on
     treatment with hydrogen bromide. When B is warmed with aqueous sodium hydroxide, it is
     converted into C, C6H12O. Compound C is not easily oxidised, but vigorous conditions cause
     the ring to open to form CH3CO(CH2)3COOH. When C is treated with concentrated sulphuric
     acid, A is reformed together with compound D, C6H10.

      Compound C has a broad absorption band at 3350 cm–1 in its infra-red spectrum. Compound D
      has an absorption band at approximately 1650 cm–1.

      Use the data in the Table, as well as the information provided in the question, to deduce
      structures for compounds A, B, C and D, respectively. Name the types of reaction taking place
      and outline a mechanism to account for the formation of compound B. Wherever possible,
      explain the significance of the information provided in the question.




Table of infra-red

absorption data




(Total 15 marks)




                                                                                                                                                     10
Topic 6 Halogenoalkanes

Q19) Which one of the following chlorine compounds is not hydrolysed by water at room
     temperature?

      A     CH3Cl

      B     CH3COCl

      C     AlCl3

      D     PCl5




Q20) Which one of the following is not a suitable method for the preparation of ethanol?

      A     oxidation of ethane

      B     hydration of ethene

      C     reduction of ethanal

      D     hydrolysis of bromoethane




Q21) In which one of the Following are the curly arrows not used correctly?

      A


      B


      C



      D



Q22) (a)    Give the structural formula of 2-bromo-3-methylbutane.




                                                                                           (1)


                                                                                           11
      (b)   Write an equation for the reaction between 2-bromo-3-methylbutane and dilute aqueous
            sodium hydroxide. Name the type of reaction taking place and outline a mechanism.

            Equation .....................................................................................................................

            .....................................................................................................................................

            Type of reaction ..........................................................................................................

            Mechanism




                                                                                                                                                          (4)

      (c)   Two isomeric alkenes are formed when 2-bromo-3-methylbutane reacts with ethanolic
            potassium hydroxide. Name the type of reaction occurring and state the role of the
            reagent. Give the structural formulae of the two alkenes.

            Type of reaction ..........................................................................................................

            Role of reagent.............................................................................................................

            Structural formula of alkene 1                                               Structural formula of alkene 2




                                                                                                                                                          (4)
                                                                                                                                              (Total 9 marks)

Q23) (a)    There are eight structural isomers with the molecular formula C5H11Br. Four of these are
            classed as primary, three as secondary and one as tertiary. The graphical formula of one
            of the secondary compounds, isomer A, is shown below.



                        isomer A


            (iii)     Draw the graphical formula of the tertiary compound with molecular formula
                      C5H11Br, isomer B.




                                                                                                                                                          12

				
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