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									        Name : ..................................................................                             Grade 11 ..................

                                                                                                   Topic 1.7 Alkenes
                                                                 Worksheet 1

  1.    But-2-ene, C4H8, is used by the petrochemical industry to produce many useful
        materials. Draw structures to represent possible compounds A-D in the reactions of
        but-2-ene shown below.




                                                                                                 Bromine
                                                                                                  water




(e)     But-2-ene can be converted into buta-1,3-diene by a process called dehydrogenation.
        Buta-1,3-diene is used to make synthetic rubber.

        (i) Suggest the structure of buta-1,3-diene.



        (ii) Construct an equation for the dehydrogenation of but-1-ene to form buta-1,3-diene.

        ............................................................................................................................. ..      [2]




LAS –Chemistry 2008-2009                                [ Topic 1.7 Alkenes WS1 ]                                           Mr. Tarek Aoudi     1
  2.    But-1-ene undergoes the following reactions:


       CH3CH2CH2CH3                    Reaction 1          CH3CH2CH=CH2                       Reaction 2                 compound A
                                                                but-1-ene                                               (major product)


                                                                          Reaction 3




                                                      CH3CH2CH(OH)CH2OH


       (a)   State the reagent and conditions needed for Reaction 1.

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

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

       (b)   (i)      The reagent in Reaction 2 is gaseous hydrogen bromide.

                      Draw the full structural formula of compound A.




                                                                                                                                                     (1)

             (ii)     What type of reagent is hydrogen bromide in this reaction?

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

       (c)   Identify the reagent needed for Reaction 3.

             .....................................................................................................................................
                                                                                                                                                     (1)
       (d)   But-1-ene can be used to make an addition polymer.

             Draw the repeating unit of the polymer.
                                                                                                                                                     (2)




LAS –Chemistry 2008-2009                                [ Topic 1.7 Alkenes WS1 ]                                                Mr. Tarek Aoudi      2
  3.    (a)          But-2-ene, CH3CH = CHCH3, exists as geometric isomers.

              (i)      Draw the geometric isomers of but-2-ene.




                                                                                                                                                   (2)

              (ii)     Explain how geometric isomerism arises.

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

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

       (b)    (i)      Draw the structural formula of a compound which is an isomer of but-2-ene
                       but which does not show geometric isomerism.




                                                                                                                                                   (1)

              (ii)     Explain why the isomer drawn in (i) does not show geometric isomerism.

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

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


        (c) (i)        State the general formula of alkenes to which but –2–ene belong.




              (ii)     State the general formula of alkenes to which cyclo butene belong.




LAS –Chemistry 2008-2009                                 [ Topic 1.7 Alkenes WS1 ]                                               Mr. Tarek Aoudi    3
  4.    Myrcene is naturally occurring oil present in bay leaves. The structure of myrcene is shown
        below.




        (a)      State the molecular formula of myrcene.
                 ...............................................................................................................................[1]

        (b)      Reaction of a 0.100 mol sample of myrcene with hydrogen produced a saturated
                 alkane A.

        (i)      Explain what is meant by the term saturated alkane;

                   A hydrocarbon that contains no double bond / max number of hydrogens /
                   single bonds only


        (ii)      Determine the molecular formula of the saturated alkane A;


        (iii)    Construct a balanced equation for this reaction.
                 ...............................................................................................................................

        (iv)     Calculate the volume of hydrogen, measured at room temperature and pressure
                 (r.t.p.),that reacted with the sample of myrcene.

                 [1 mole of gas molecules occupy 24.0 dm3 at r.t.p.]
                                                                                                                                                      [5]




                                                                                                                                    Ans : 7.2 dm3



LAS –Chemistry 2008-2009                               [ Topic 1.7 Alkenes WS1 ]                                                Mr. Tarek Aoudi         4
        (c)          Squalene is a naturally occurring oil present in shark liver oil. A 0.100 mol sample of
                     squalene reacted with 14.4 dm3 of hydrogen, measured at r.t.p., to form a saturated
                     hydrocarbon C30H62.

                     (i) Calculate how many double bonds there are in each molecule of squalene.


                     (ii) Suggest the molecular formula of squalene.

                     ...............................................................................................................................[3]


  5. (a) Myrcene, C10H16, (Mr = 136) is a compound produced by pine trees in North America
         Unfortunately, it attracts females of the beetle, which lays eggs in the tree. The
         drilling of the tree injects a pathogenic fungus, causing the tree's death.

                                                               CH 2

                                                               C

                                                       CH 2          CH

                                                       CH 2          CH 2

                                                               CH

                                                               C                     Myrcene

                                                       CH 3           CH 3



              (i)        State what you would see when bromine dissolved in an inert organic solvent
                         is added to myrcene.

                         …………………………………………………………………………………
                                                                                                                                                          (1)
                                                                                                                                     –3
              (ii)       A sample of myrcene weighing 2.72 g is reacted with a 1.00 mol dm
                                                     3
                         solution of bromine; 60.0 cm was required. Show that this is consistent with
                         the structure of myrcene.
                                                                                                                                                          (3)




LAS –Chemistry 2008-2009                                   [ Topic 1.7 Alkenes WS1 ]                                              Mr. Tarek Aoudi          5
             (iii) Given that 1.44 dm3 of hydrogen reacts with 2.72 g of myrcene in the
                   presence of a platinum catalyst, draw the structure of the product.
                                                                                                     3
                     The molar volume of hydrogen at the temp & pressure of the experiment is 24 dm .
                                                                                                             (2)




      (b)    Myrcene reacts with hydrogen bromide to give B:


                                                      CH 3

                                                      C      Br

                                               CH 2          HC       Br

                                               CH 2          CH 3

                                                      CH 2

                                                      C      Br

                                             CH 3            CH 3



             The double bonds can be regenerated by an elimination reaction; one elimination
             product among many is C:


                                                        CH 3

                                                        C

                                                 CH           CH

                                                 CH 2         CH 2

                                                        CH

                                                        C
                                                 CH 3          CH 3




LAS –Chemistry 2008-2009                   [ Topic 1.7 Alkenes WS1 ]                       Mr. Tarek Aoudi    6
             (i)     State the reagents and conditions required to form C from B.

                     …………………………………………………………………………………

                     …………………………………………………………………………………
                                                                                                         (2)

             (ii)    Explain why products other than myrcene itself are produced in this
                     elimination reaction.

                     …………………………………………………………………………………

                     …………………………………………………………………………………

                     …………………………………………………………………………………
                                                                                                         (2)

             (iii) What type of isomerism is shown by the bromo compound B which is not
                   shown by myrcene itself? Give a reason.

                     …………………………………………………………………………………

                     …………………………………………………………………………………
                                                                                                         (2)




LAS –Chemistry 2008-2009                  [ Topic 1.7 Alkenes WS1 ]                    Mr. Tarek Aoudi    7
  6.    Myrcene is a naturally-occurring oil present in bay leaves. It can be used in perfumes to give
        a spicy character. The structure of myrcene is shown below.




  (a) Name the functional group present in myrcene.

        ............................................................................................................................................ [1]

  (b)   Information about the structure of myrcene can be obtained by reacting it with bromine to
        produce the saturated organic compound A.

        (i)        State the colour change you would see when bromine reacts with myrcene.

                   from ........................................................... to ............................................................[2]

        (ii)       Circle two words from the following list that best describe what is happening in the
                   reaction of myrcene with bromine.

                  addition          electrophilic elimination nucleophilic                                 radical            substitution

                                                                                                                                                      [2]
        (iii)      Write a balanced equation for the reaction of myrcene, C10H16, with bromine to
                   produce the fully saturated compound A. Use the molecular formulae of the
                   molecules.                                                                                                                         [2]




LAS –Chemistry 2008-2009                                  [ Topic 1.7 Alkenes WS1 ]                                              Mr. Tarek Aoudi           8
  7.    Isoprene is an alkene that can be tapped from some trees. It is the monomer in natural
        rubber. Limonene is a natural oil found in the rind of oranges and lemons.
        Both isoprene and limonene contain two double bonds.

        Their structural and skeletal formulae are shown below




(a)     (i) What is the molecular formula of isoprene? ......................................................... [1]

        (ii) What is the empirical formula of limonene? ......................................................... [1]

(b)     In the presence of a suitable catalyst, isoprene and limonene both react with hydrogen.


        (i) State a suitable catalyst for this reaction. ......................................................... [1]


        (ii) Write an equation for the reaction when isoprene reacts completely with hydrogen.




        (iii) Draw the skeletal formula of a product formed when limonene reacts partially with
              hydrogen.




LAS –Chemistry 2008-2009                         [ Topic 1.7 Alkenes WS1 ]                                   Mr. Tarek Aoudi   9
  8.     Dodec-1-ene has the structure shown.

                                                      CH3(CH2)9CH = CH2

      (a) Draw the structures of the organic molecules produced when dodec-1-ene reacts with
          each of the following.


            (i) liquid bromine                                                      (ii) hydrogen bromide




            (iii) dilute manganate(VII) ions                                        (iv) steam




(b) (i) What type of isomerism is shown by the organic products in (i), (ii) and (iv)?

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

   (ii) Draw structures to represent these isomers, choosing any one of these products.




(c)      Dodec-2-ene shows another type of isomerism. Draw and label diagrams which show
         these two isomers.




LAS –Chemistry 2008-2009                                [ Topic 1.7 Alkenes WS1 ]                                           Mr. Tarek Aoudi   10
  9.    Compound A is a chloroalkene with the percentage composition by mass:
        C, 24.7% ; H, 2.1% ; Cl, 73.2%.

        (a) (i) Calculate the empirical formula of compound A. Show your working.                    [2]




            (ii) The relative molecular mass of compound A is 145.5. Show that the molecular
                 formula is C3H3Cl3.                                                         [2]


        (b) Compound A is one of six possible structural isomers of C3H3Cl3 that are
            chloroalkenes. Two of these isomers are shown below as isomer 1 and isomer 2.




        (i) Draw two other structural isomers of C3H3Cl3 that are chloroalkenes.




LAS –Chemistry 2008-2009              [ Topic 1.7 Alkenes WS1 ]                    Mr. Tarek Aoudi    11
  10. Cis-hex-3-en-1-ol is a colourless liquid also known as leaf alcohol. It has a powerful
      smell of newly cut grass and it occurs naturally in a variety of plants, such as geranium,
      thyme and tea. The structural formula of leaf alcohol is shown below.




        (a) Draw the organic product(s) formed when leaf alcohol reacts with


         (i) hydrogen in the presence of a suitable catalyst,




         (ii) hydrogen bromide.




LAS –Chemistry 2008-2009                [ Topic 1.7 Alkenes WS1 ]                Mr. Tarek Aoudi   12
(b)     Leaf alcohol reacts with bromine as shown in the equation below.




(i)     State what you would see when bromine reacts with leaf alcohol.

        ...............................................................................................................................1]

(ii)    Complete, with the aid of curly arrows, the mechanism involved in the reaction
        between leaf alcohol and bromine. Show any relevant dipoles, charges and lone pairs of
        electrons.




LAS –Chemistry 2008-2009                                 [ Topic 1.7 Alkenes WS1 ]                                              Mr. Tarek Aoudi   13
  11. Sorbic acid has the formula : H3C CH = CH CH = CH COOH ; it reacts with bromine ( Br2)
      in tetrachloromethane.

(a)     Write an equation, using structural formula for the complete reaction of sorbic acid with
        bromine. State your observations and give the name of the product.


        Equation : ………………………………………………………………………………

        Observations : ………………………………………………………………………….

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

        Name of the product : ………………………………………………………………….

(b)     Sorbic acid can show geometric isomerism

        Explain carefully why sorbic acid shows geometric isomerism.

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

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

        State, with a reason, the number of geometric isomers that sorbic acid has.

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




LAS –Chemistry 2008-2009                  [ Topic 1.7 Alkenes WS1 ]                   Mr. Tarek Aoudi   14
   12. Some perfumes and scents of flowers and fruit contain compounds which are structural
       isomers. Two such examples are citronellol and geraniol.




                                               citronellol                                                   geraniol


   (a) Confirm that citronellol and geraniol are isomers by calculating their molecular formula
       and their relative molecular mass, Mr.

   (i) Molecular formula .....................................................................................................

   (ii) Mr ..........................................................................................................................[2]


 (b) Name two functional groups present in both molecules.

   (i) ....................................................................................................................................

   (ii) ................................................................................................................................[3]


(c) Draw the other cis-trans isomer of geraniol. [Use R – to represent a part of the molecule.]




(e) State what you would expect to see if citronellol was reacted with aqueous bromine.

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

.....................................................................................................................................[1]




LAS –Chemistry 2008-2009                                     [ Topic 1.7 Alkenes WS1 ]                                               Mr. Tarek Aoudi   15
(f) Draw structures of the organic products when geraniol reacts with each of the following
    reagents.


   (i) bromine water




   (ii) hydrogen bromide, HBr




LAS –Chemistry 2008-2009               [ Topic 1.7 Alkenes WS1 ]                    Mr. Tarek Aoudi   16

								
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