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					                                                Chapter 8



MULTIPLE CHOICE QUESTIONS

Topic: Structure Elucidation

    1. An alkene adds hydrogen in the presence of a catalyst to give 3,4-dimethylhexane.
       Ozonolysis of the alkene followed by treatment with zinc and acetic acid gives a single
       organic product. The structure of the alkene is:
    A)           CH3
         CH3CH=C-CHCH2CH3           (cis or trans)
                    CH3
    B)            CH3
         CH3CH2C=CCH3          (cis or trans)
                    CH2CH3
    C)        CH3
         CH2=CCH2CHCH2CH3
                    CH3
    D)            CH2
         CH3CH2CCHCH2CH3
                   CH3
    E)            CH3
         CH3CH2CHCHCH=CH2
                    CH3
         Ans: B




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                                                 Chapter 8



Topic: Structure Elucidation

    2. Ozonolysis of compound Z yields the products shown below. What is the structure of Z?
                                             O               O         O
                       1) O3
                   Z                     2HCH + CH3CCH2CH
                       2) Zn, HOAc


                                                             O


                       I                II                       III
                                O

                                    H

                           IV                         V


    A)   I
    B)   II
    C)   III
    D)   IV
    E)   V
         Ans: B




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                                           Chapter 8



Topic: Structure Elucidation

    3. Compound C has the molecular formula C7H12. On catalytic hydrogenation, 1 mol of C
       absorbs 1 mol of hydrogen and yields a compound with the molecular formula C7H14.
       On ozonolysis and subsequent treatment with zinc and acetic acid, C yields only:
                                    O
                                                       O


         The structure of C is:


           I               II              III




                  IV                 V
    A)   I
    B)   II
    C)   III
    D)   IV
    E)   V
         Ans: E

Topic: Structure Elucidation


    4. Compound X has the molecular formula C6H10. X decolorizes bromine in carbon
       tetrachloride. X also shows IR absorption at about 3300 cm-1. When treated with
       excess hydrogen and a nickel catalyst, X yields 2-methylpentane. The most likely
       structure for X is:
    A)

    B)

    C)

    D)

    E)

         Ans: D




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                                        Chapter 8



Topic: Structure Elucidation

    5. An unknown compound, A, has the molecular formula C7H12. On oxidation with hot
       aqueous potassium permanganate, A yields CH3CH2COOH and (CH3)2CHCOOH.
       Which of the following structures best represents A?
    A)

    B)

    C)

    D)

    E)

         Ans: C




                                          244
                                                 Chapter 8



Topic: Structure Elucidation

    6. Determine a possible structure for an alkene, X, formula C9H14, on the basis of the
       following information: X adds one mole of hydrogen on catalytic hydrogenation. On
       treatment with hot basic KMnO4 followed by acidification, X yields the following
       dicarboxylic acid.
                               HO            O

                                  O          OH

         A possible structure for X might be:




              I              II                    III




                    IV                   V

    A)   I
    B)   II
    C)   III
    D)   IV
    E)   V
         Ans: C

Topic: Structure Elucidation

    7. An optically active compound, Y, with the molecular formula C7H12 gives a positive test
       with cold dilute KMnO4 and shows IR absorption at about 3300 cm-1. On catalytic
       hydrogenation, Y yields Z(C7H16) and Z is also optically active. Which is a possible
       structure for Y?
    A) CH3CH2CH2CH2CH2CCH
    B) (CH3)2CHCH2CH2CCH
    C) CH3CH2CH(CH3)CH2CCH
    D) CH3CH2CH(CH3)CCCH3
    E) CH2=CHCH(CH3)CH2CH=CH2
       Ans: C




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                                                Chapter 8



Topic: Structure Elucidation

    8. One mole of an optically active compound, X, with the molecular formula C6H8 reacts
       with three moles of hydrogen in the presence of a catalyst to yield an optically inactive
       product that cannot be resolved. X also exhibits IR absorption at approximately 3300
       cm-1. Which is a possible structure for X?
    A) (E)-4-hexen-1-yne
    B) (Z)-4-hexen-1-yne
    C) (E)-2-hexen-4-yne
    D) 2-methyl-1-penten-3-yne
    E) 3-methyl-1-penten-4-yne
       Ans: E

Topic: Structure Elucidation

    9. An alkene with the molecular formula C10H18 is treated with ozone and then with zinc
       and acetic acid. The product isolated from these reactions is:

                         O
         O


         What is the structure of the alkene?



                  I                        II                    III




                               IV                           V

    A)   I
    B)   II
    C)   III
    D)   IV
    E)   V
         Ans: C




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                                              Chapter 8



Topic: Structure Elucidation

   10. An optically active compound, A, with the molecular formula C7H12 reacts with cold
       dilute KMnO4 and gives IR absorption at about 3300 cm-1. On catalytic hydrogenation,
       A is converted to B (C7H16) and B is also optically active. Which is a possible structure
       for A?



                  I                      II                           III




                             IV                       V

    A)   I
    B)   II
    C)   III
    D)   IV
    E)   V
         Ans: E

Topic: Structure Elucidation

   11. Which substance would undergo the following reaction?

                 i. O3                                        H
             ?   ii. Zn, HOAc                   +
                                  O                       H       O

    A)   4-Hexen-1-yne
         r




    B)   3-methyl-1-hexene
    C)   (E)-2-hexene
    D)   (Z)-2-hexene
    E)   4-methyl-1-hexene
         Ans: E




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                                          Chapter 8



Topic: Structure Elucidation

   12. Which alkene would yield only CH3CH2COOH on oxidation with hot alkaline
       potassium permanganate (followed by acid work-up)?
   A) (E)-2-hexene
    B) (Z)-2-hexene
    C) 2-methyl-2-pentene
   D) (E)-3-hexene
    E) (E)-4-methyl-2-pentene
       Ans: D

Topic: Structure Elucidation

   13. An unknown compound, B, has the molecular formula C7H12. On catalytic
       hydrogenation 1 mol of B absorbs 2 mol of hydrogen and yields 2-methylhexane. B has
       significant IR absorption band at about 3300 and 2200 cm-1. Which compound best
       represents B?
   A) 3-methyl-1-hexyne
    B) 5-methyl-2-hexyne
    C) 5-methyl-1,3-hexadiene
   D) 5-methyl-1-hexyne
    E) 2-methyl-1,5-hexadiene
       Ans: D

Topic: Structure Elucidation

   14. What compound would yield an equimolar mixture of CH3CH2CH2CHO and CH3CHO
       upon treatment with O3, followed by Zn/HOAc?
   A) 1-Hexene
    B) cis-2-Hexene
    C) trans-2-Hexene
   D) More than one of these
    E) None of these
       Ans: D

Topic: Structure Elucidation

   15. An alkene with the molecular formula C8H16 undergoes ozonolysis to yield a mixture of
       (CH3)2C=O and (CH3)3CCHO. The alkene is:
   A) 2,2-Dimethyl-2-hexene
    B) 2,3-Dimethyl-2-hexene
    C) 2,4-Dimethyl-2-hexene
   D) 2,4,4-Trimethyl-2-pentene
    E) More than one of the above is a possible answer.
       Ans: D




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                                            Chapter 8



Topic: Structure Elucidation

   16. Which of the following would decolorize bromine in carbon tetrachloride and yield a
       ketone upon reaction with sulfuric acid in the presence of catalytic amounts of HgSO4?
   A) CH3CH=CHCH3
    B) CH3CH=CH2
    C) CH3CH2CCH
   D) CH3CH2CH2CH3
    E) All of these would give positive results in each test.
       Ans: C

Topic: Structure Elucidation

   17. Which of these compounds will react with cold concd. H2SO4, as well as Br2 in CCl4 ?

    A)   CH3CH2CH=CHCH3
    B)   CH3CH2CH2CH=CH2
    C)   CH3CH2CCCH3
    D)   (CH3)2CHCCH
    E)   All of these
         Ans: E

Topic: Structure Elucidation

   18. Which of the following reagents might serve as the basis for a simple chemical test that
       would distinguish between pure 1-pentene and pure pentane?
   A) Bromine in carbon tetrachloride
    B) Dilute aqueous potassium permanganate
    C) Concentrated sulfuric acid
   D) All of the above
    E) Answers A) and B) only
       Ans: D

Topic: Structure Elucidation

   19.   Which reagent or test could be used to distinguish between 3-pentyne and 1-pentyne?
   A)    Br2/CCl4
    B)   IR examination
    C)   Concd. H2SO4
   D)    KMnO4,OH-
    E)   None of these
         Ans: B




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                                            Chapter 8



Topic: Structure Elucidation

   20. Which reagent or test could be used to distinguish between 2-methyl-2-pentene and 2-
       methylpentane?
   A) Br2/CCl4
    B) KMnO4, OH
    C) Concd. H2SO4
   D) Two of the above
    E) All of the above
       Ans: E


Topic: Structure Elucidation

   21.   Which of the following could be used to distinguish between 1-octyne and 3-octyne?
   A)    Treatment with 2 mol of HX
    B)   Addition of water
    C)   Reaction with KMnO4
   D)    Decolorization of bromine in CCl4
    E)   IR examination
         Ans: E

Topic: Structure Elucidation

   22. A reagent or test that could be used to distinguish between 1-pentene and 1-pentyne
       would be:
   A) Bromine in carbon tetrachloride
    B) Dilute aqueous potassium permanganate
    C) CrO3 in H2SO4
   D) H2SO4
    E) IR examination
       Ans: E

Topic: Structure Elucidation

   23. Which of the following could be used as the basis for a simple test that would
       distinguish between 1-pentyne and pentane?
   A) IR examination
    B) Br2/CCl4
    C) KMnO4/H2O
   D) Two of these
    E) All of these
       Ans: E




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                                                 Chapter 8



Topic: Reaction Products

   24. Treating 1-methylcyclohexene with H3O+ would yield primarily which of these?

        HO                            HO
                                                                  HO

              I                             II                               III

                            HO
                                                             OH

                                 IV                      V
   A)   I and V
   B)   II
   C)   III and V
   D)   IV
   E)   I, III and V
        Ans: D

Topic: Reaction Products

   25. What would be the major product of the following reaction?
                         HCl



                                            Cl                               Cl
                  Cl                                                              Cl


          I                            II                              III

                       Cl
                                                             Cl

                            IV                     V
   A)   I
   B)   II
   C)   III
   D)   IV
   E)   V
        Ans: B




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                                                  Chapter 8



Topic: Reaction Products

   26. Treating 1-methylcyclohexene with HCl would yield primarily which of these?
        H3C                         H3C                          H3C
                                                                  Cl
         Cl                            Cl

              I                              II                         III
                       H3C        Cl              Cl


                             IV                              V

   A)   I
   B)   II
   C)   III
   D)   IV
   E)   V
        Ans: C

Topic: Reaction Products

   27. Which product would you expect from the following reaction?

                             H3O+
                             H2O


                                                                        OH

                  OH
                                            OH
          I                            II                         III


                              OH

                        IV                             V

   A)   I
   B)   II
   C)   III
   D)   IV
   E)   V
        Ans: D




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                                                 Chapter 8



Topic: Reaction Products

   28. The reaction of Br2/CCl4 to cyclohexene would produce the compound(s) represented
       by structure(s):

              H                       H                                         H
                       H                        Br                   Br
         Br                      Br                                                 Br
                  Br                       H                              H
                I                     II                                      III
   A)   I alone
   B)   II alone
   C)   II and III
   D)   III alone
   E)   I , II and II
        Ans: C

Topic: Reaction Products

   29. What product would you expect from addition of deuterium chloride to 2-cyclohexyl-4-
       methyl-2-pentene?
                                                 Cl                                        D
        D
                                                D H                                        Cl
                      Cl

                  I                        II                                        III
                            Cl


                            D                                    D
                                                            Cl
                           IV                                    V

   A)   I
   B)   II
   C)   III
   D)   IV
   E)   V
        Ans: B




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                                                Chapter 8



Topic: Reaction Products

   30.   What is the chief product of the reaction of IBr with 2-methyl-2-pentene?
   A)    2-bromo-3-iodo-2-methylpentane
    B)   3-bromo-2-iodo-2-methylpentane
    C)   1-bromo-2-iodo-2-methylpentane
   D)    2-bromo-1-iodo-2-methylpentane
    E)   All of the above
         Ans: A

Topic: Reaction Products

   31.   What is the chief product of the acid-catalyzed hydration of 2,5-dimethyl-2-hexene?
   A)    2,5-dimethyl-1-hexanol
    B)   2,5-dimethyl-2-hexanol
    C)   2,5-dimethyl-3-hexanol
   D)    2,5-dimethyl-2,3-hexanediol
    E)   2,5-dimethyl-3,4-hexanediol
         Ans: B

Topic: Reaction Products

   32. What product would result from the following reaction?

                            KMnO4, H2O
                                            ?
                            cold, dilute


                     CO2H
                 O
                                    K    MnO4               OH OH

             I                      II                      III


                         OH OH                    OH OH
                         IV                       V

   A)    I
   B)    II
   C)    III
   D)    IV
   E)    V
         Ans: C




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                                                  Chapter 8



Topic: Reaction Products

   33.   Acid-catalyzed hydration of 2-methyl-1-butene would yield which of the following?
   A)    (CH3)2C(OH)CH2CH3
    B)   CH2OHCH(CH3)CH2CH3
    C)   (CH3)2CHCHOHCH3
   D)    (CH3)2CHCH2CH2OH
    E)   CH3CH2CH(CH3)CH2OH
         Ans: A

Topic: Reaction Products

   34. Which of these is not formed when cyclopentene reacts with an aqueous solution of
       bromine?
                    Br          OH                Br                Br        OH
               OH          Br            Br                    Br        OH
           I             II            III                    IV         V

   A)    I
   B)    II
   C)    III
   D)    IV
   E)    V
         Ans: E

Topic: Reaction Products

   35. What would be the major product of the following reaction?
                                        Br2, H2O
                                                          ?


                    Br          Br                OH                Br        OH

               OH          Br                Br                Br            OH
           I             II            III                    IV         V

   A)    I
   B)    II
   C)    III
   D)    IV
   E)    V
         Ans: A




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                                               Chapter 8



Topic: Reaction Products

   36. Addition of hydrogen chloride to the following molecule would produce:
                                               HCl
                                                         ?
                                   Cl
          Cl             Cl              Cl                Cl
                                                                            Cl
               Cl             Cl              Cl                Cl    Cl
               I              II           III                  IV    V

   A)   I and II
   B)   II and III
   C)   I and IV
   D)   V
   E)   All of the above are equally likely to be formed
        Ans: A




                                                   256
                                                          Chapter 8



Topic: Reaction Products

   37. In addition to the expected major product, which compound may be reasonably
       anticipated as a by-product in the hydroxylation of R-2-methylcyclohexene with cold
       alkaline permanganate?

              H3C         H        i. KMnO4, H2O
                                     cold, dilute
                                                          ?
                                             +
                                   ii. H3O

        H3C       H                   H3C         H
                      OH                              OH
                                                                      H3C    H
                                                      H               O
                      OH                                                               O
              I                                  II                              III


                      H    CH3                            H    CH3          OH
                  O                                   O
                                       O                                     O
                                                          OH
                              IV                                    V

   A)   I
   B)   II
   C)   III
   D)   IV
   E)   V
        Ans: E




                                                              257
                                                Chapter 8



Topic: Reaction Products

   38. Select the structure of the major product formed in the following reaction.
                            2 HCl
                                            ?

                                       Cl

                   Cl                                                       Cl
                                                                       Cl
           I                      II                             III
                        Cl   Cl                       Cl
                                                            Cl

                        IV                       V

   A)   I
   B)   II
   C)   III
   D)   IV
   E)   V
        Ans: D

Topic: Reaction Products

   39. Which of these compounds is not formed when gaseous ethene is bubbled into an
       aqueous solution of bromine, sodium chloride and sodium nitrate?
   A) BrCH2CH2Br
    B) BrCH2CH2Cl
    C) BrCH2CH2OH
   D) ClCH2CH2OH
    E) BrCH2CH2ONO2
       Ans: D




                                                  258
                                                   Chapter 8



Topic: Reaction Products

   40. Select the structure of the major product formed in the following reaction.

                             2 Cl2
                                               ?

                                          Cl                           Cl   Cl
                   Cl                                                            Cl
                                          Cl                                Cl
           I                         II                              III
                        Cl   Cl                            Cl
                                                                Cl

                        IV                           V
   A)   I
   B)   II
   C)   III
   D)   IV
   E)   V
        Ans: C




                                                     259
                                                    Chapter 8



Topic: Reaction Products

   41. Addition of excess HBr to 2-methyl-3-heptyne would produce:

        2-methyl-3,3-dichloroheptane            2-methyl-2,3-dichloroheptane

                     I                                               II


        2-methyl-4,4-dichloroheptane                2-methyl-3,4-dichloroheptane

                     III                                             IV


        2-methyl-3-chloroheptene

                     V

   A)   I and II
   B)   I and III
   C)   II and IV
   D)   V
   E)   All of the above
        Ans: B

Topic: Reaction Products

   42. What would be the major product of the following reaction?
                                  Br2, CCl4
                                                                 ?


            CH3                 CH3           CH3                     CH3
        H       Br         Br        H    H          Br         Br         H
        H       Br         Br        H   Br          H           H         Br
            C3H7                C3H7          C3H7                    C3H7

            I                   II            III                     IV

   A)   Equal amounts of I and II
   B)   Equal amounts of II and III
   C)   Equal amounts of III and IV
   D)   I and II as major products, III and IV as minor products
   E)   All of the above in equal amounts
        Ans: A




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                                               Chapter 8



Topic: Reaction Products

   43. What would be the major product of the following reaction?
                                          Br2, CCl4
                                                                ?


                C2H5            C2H5            C2H5                C2H5
        H3C         Br    Br         CH3 H3C         Br     Br           CH3
            H       Br    Br         H    Br         H          H        Br
                C3H7            C3H7            C3H7                C3H7

                I               II             III                  IV

   A)   Equal amounts of I and II
   B)   Equal amounts of II and III
   C)   Equal amounts of III and IV
   D)   I and II as major products, III and IV as minor products
   E)   All of the above in equal amounts
        Ans: A

Topic: Reaction Products

   44. Hydroxylation of cis-2-pentene with cold alkaline KMnO4 yields

            CH3               CH3             CH3               CH3
        H       OH       HO     H         H     OH         HO       H
        H       OH       HO     H        HO     H           H       OH
            C2H5              C2H5            C2H5              C2H5

            I               II              III           IV
   A)   Equal amounts of I and II
   B)   Equal amounts of II and III
   C)   Equal amounts of III and IV
   D)   I and II as major products, III and IV as minor products
   E)   All of the above in equal amounts
        Ans: B




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                                                                   Chapter 8



Topic: Reaction Products

   45. The reaction of BrCl (bromine monochloride) with 1-methylcyclopentene will produce
       as the predominant product:

                          CH3               CH3                      CH3                    CH3         CH2Cl
                          Br                                         Br                     Cl          Br
                                             Cl
                     Cl                    Br                Cl                       Br
           +                        +                      +                       +                 +
        enantiomer               enantiomer             enantiomer              enantiomer        enantiomer
                 I                    II                     III                  IV                V
   A)   I
   B)   II
   C)   III
   D)   IV
   E)   V
        Ans: D

Topic: Reaction Products

   46. Reaction of trans-2-hexene with a solution of Br2 in CCl4 produces:
             H                                Br                                      H
        Br                                   H                                   Br
                          Br                             H                                   H
                      H                                 Br                                  Br
                 I                                 II                                     III
                            Br
                           H
                                      Br                      H             H
                                  H                            Br         Br
                                 IV                                   V
   A)   I and II
   B)   II and V
   C)   III and IV
   D)   IV and V
   E)   V
        Ans: C




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                                            Chapter 8



Topic: Reaction Products

   47. When either cis- or trans-2-butene is treated with hydrogen chloride in ethanol, the
       product mixture that results includes:
   A) CH3CH2CH2CH2Cl
    B) CH3CH2CH2CH2OCH2CH3
    C) CH3CH2CH(CH3)OCH2CH3
   D) (CH3)3CCl
    E) (CH3)2CHCH2OCH2CH3
       Ans: C

Topic: Reaction Products

   48. What is the major product of the following reaction?
                       H2SO4, H2O
                                         ?
                       HgSO4

                OH                                                OH
                     OH                   OH

            I                     II                        III
                           O
                                                        O


                      IV                     V
   A)    I
   B)    II
   C)    III
   D)    IV
   E)    V
         Ans: D

Topic: Reaction Products

   49.   Addition of 2 mol of HCl to 1-butyne would yield:
   A)    CH3CH2CH2CHCl2
    B)   CH3CH2CCl2CH3
    C)   CH3CH2CHClCH2Cl
   D)    CH3CH2CH=CHCl
    E)   CH3CHClCHClCH3
         Ans: B




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                                              Chapter 8



Topic: Reaction Products

   50. Consider the addition of HCl to 3-methyl-1-butene. The major product of the reaction
       would be:
   A) 1-Chloro-2-methylbutane
    B) 1-Chloro-3-methylbutane
    C) 2-Chloro-2-methylbutane
   D) 2-Chloro-3-methylbutane
    E) 1-Chloropentane
       Ans: C

Topic: Reaction Products

   51. What is the final product of the following synthesis?

                         H2              i. OsO4
              2-Butyne              C4H8                       Final Product
                         Ni2B (P-2)      ii. NaHSO4


              CH3                CH3                  CH3               CH3
         HO      OH         HO      H          HO        H          H      OH



          H      H          HO      H            H       OH       HO       H
              CH3                CH3                  CH3               CH3


              I                  II                   III               IV

    A)   I
    B)   II
    C)   III
    D)   IV
    E)   An equimolar mixture of III and IV
         Ans: B

Topic: Synthetic Strategy

   52. A synthetic strategy for converting trans-2-butene into pure cis-2-butene would consist
       of which of the following?
   A) Reaction with H2, Ni2B (P-2)
    B) Reaction with i) Br2, CCl4; ii) 2 NaNH2, NH3(l); iii) Na, NH3 (l)
    C) Reaction with H3O+, heat
   D) Reaction with i) Br2, CCl4; ii) 2 NaNH2, NH3(l); iii) H2, Ni2B (P-2)
    E) None of these will successfully effect the desired transformation
       Ans: D




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                                            Chapter 8



Topic: Synthetic Strategy

   53. Which reagent(s) given below could be used to synthesize cis-1,2-cycloheptanediol
       from cycloheptene?
   A) KMnO4, OH, 5oC
    B) KMnO4, H3O+, 75oC
    C) H2SO4, heat
   D) All of these
    E) None of these
       Ans: A

Topic: Synthetic Strategy

   54.   Which reaction sequence would convert cis-2-butene to trans-2-butene?
   A)    Br2/CCl4; then 2 NaNH2; then H2/Ni2B(P-2)
    B)   Br2/CCl4; then 2 NaNH2; then Li/liq. NH3
    C)   H3O+, heat; then cold dilute KMnO4
   D)    HBr; then NaNH2; then H2, Pt
    E)   None of these
         Ans: B

Topic: Synthetic Strategy

   55. The conversion of ethylene to vinyl bromide can be accomplished by use of these
       reagents in the order indicated.
   A) (1) HBr; (2) NaOC2H5
    B) (1) Br2; (2) NaOC2H5
    C) (1) Br2; (2) H2O
   D) (1) NaNH2; (2) HBr
    E) (1) HBr; (2) H2SO4
       Ans: B

Topic: Synthetic Strategy

   56. Cyclohexene is treated with cold dilute alkaline KMnO4. Assuming syn addition, the
       spatial arrangement of the two hydroxyl groups in the product would be:
   A) equatorial-axial
    B) axial-axial
    C) equatorial-equatorial
   D) coplanar
    E) trans
       Ans: A




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                                            Chapter 8




Topic: Synthetic Strategy

   57.   Which of the following reactions of cyclobutene would yield a meso product?
   A)    Reaction with H3O+, H2O
    B)   Reaction with Br2, CCl4
    C)   Reaction with Cl2, CCl4
   D)    Reaction with D2, Pt
    E)   Reaction with hot, alkaline KMnO4, followed by acid workup
         Ans: E

Topic: Reaction Products

   58. How many compounds are possible from the addition of bromine to CH2=CHCH2CH3
       (counting stereoisomers separately)?
   A) One
    B) Two
    C) Three
   D) Four
    E) Five
       Ans: B

Topic: Reaction Products

   59. Which alkene would react with cold dilute alkaline permanganate solution to form an
       optically inactive and irresolvable product?
   A)

    B)

    C)
    D)
    E)

         Ans: C




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                                             Chapter 8



Topic: Reaction Products

   60.   Which reaction of an alkene proceeds with anti addition?
   A)    Hydroboration/oxidation
    B)   Bromination
    C)   Oxidation with cold KMnO4
   D)    Hydrogenation
    E)   Oxymercuration-demercuration
         Ans: B

Topic: Reaction Products

   61.   A pair of enantiomers results from which of these reactions?
   A)    cyclopentene + cold, dil. KMnO4 
    B)   trans-2-butene + Br2 
    C)   1-pentene + HCl 
   D)    cis-2-butene + D2/Pt 
    E)   cyclobutene + OsO4, then Na2SO3 
         Ans: C

Topic: Reaction Products

   62.   Which reaction would yield a racemic product?
   A)    cyclopentene + D2/Pt 
    B)   Cyclopentene + OsO4, then Na2SO3 
    C)   cyclopentene + Br2/H2O 
   D)    Cyclopentene + cold, dilute KMnO4 
    E)   Cyclopentene + dilute H2SO4 
         Ans: C

Topic: Reaction Products

   63. 3,3-dimethylcyclohexene is subjected to reaction with cold, dilute KMnO4, to give 3,3-
       dimethyl-1,2-cyclohexanediol. In the most stable conformation of the product, the
       hydroxyl groups would be:
   A) both axial
    B) both equatorial
    C) axial-equatorial
   D) coplanar
    E) None of these
       Ans: B




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                                          Chapter 8



Topic: Reaction Products

   64. Cyclohexene reacts with bromine to yield 1,2-dibromocyclohexane. Molecules of the
       product would:
   A) be a racemic form and, in their most stable conformation, they would have both bromine
       atoms equatorial.
    B) be a racemic form and, in their most stable conformation, they would have one bromine
       atom equatorial and one axial.
    C) be a meso compound and, in its most stable conformation, it would have both bromine
       atoms equatorial.
   D) be a meso compound and, in its most stable conformation, it would have one bromine
       atom equatorial and one axial.
    E) be a pair of diastereomers and, in their most stable conformation, one would have the
       bromines equatorial and axial, and the other would have the bromines equatorial and
       equatorial.
       Ans: A

Topic: Reaction Products

   65. Which reaction would yield a meso compound?
   A)                    Br2/CCl4
       cis-2-Butene
    B)                  H2/Pd
       cis-2-Butene
    C)                  i) OsO4
       cis-2-Butene
                        ii) NaHSO3
   D)                   dil KMnO4
       trans-2-Butene        o
                            5C
    E) None of these
       Ans: C

Topic: Reaction Products

   66.   Which reaction would give a meso compound as the product?
   A)    Cyclopentene + Br2/CCl4
    B)   Cyclopentene + OsO4, then NaHSO3
    C)   Cyclopentene + RCO3H, then H3O+
   D)    Cyclopentene + Cl2, H2O
    E)   More than one of these
         Ans: B




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                                             Chapter 8



Topic: Reaction Products

   67.   Which of the following reactions would yield the final product as a racemic form?
   A)    Cyclohexene + a peroxy acid, then H3O+
    B)   Cyclohexene + cold, dilute KMnO4 and OH-
    C)   Cyclohexene + HCl
   D)    Cyclohexene + OsO4, then NaHSO3
    E)   Cyclohexene + D2/Pt
         Ans: A

Topic: Reaction Products

   68. (R)-3-Chloro-1-butene reacts with HCl by Markovnikov addition, and the products are
       separated by gas chromatography. How many total fractions would be obtained and
       how many would be optically active?
   A) One optically active fraction only
    B) One optically active fraction and one optically inactive
    C) Two optically active fractions
   D) One optically active fraction and two optically inactive
    E) Two optically active fractions and one optically inactive
       Ans: B

Topic: Reaction Products

   69. The interaction of the  bond of an alkene with an electrophile can initially result in the
       formation of a species termed a  complex. Which of these cannot combine with an
       alkene to form a  complex?
   A) H+
    B) NH3
    C) Ag+
   D) Hg2+
    E) BF3
       Ans: B

Topic: Reaction Products

   70.   Markovnikov addition of HI to 2-methyl-2-butene involves:
   A)    initial attack by an iodide ion.
    B)   initial attack by an iodine atom.
    C)   isomerization of 2-iodo-2-methylbutene.
   D)    formation of a carbocation at C-2.
    E)   formation of carbocation at C-3.
         Ans: D




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                                            Chapter 8



Topic: Reaction Products

   71. Which reaction is NOT stereospecific?

                           Br2/CCl4                                          Br2/H2O
        trans-2-Butene                                      cis-2-Pentene

                 I                                                II
                                                    H2/Pd
                         1-Methylcyclohexene

                               III

                                dil KMnO4                                     HBr
        2-Methyl-2-heptene                                  trans-2-Hexene
                                      5oC
                 IV                                               V
   A)   I
   B)   II
   C)   III
   D)   IV
   E)   V
        Ans: E




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                                                           Chapter 8



Topic: Reaction Products

   72. Which reaction is regioselective?
                                         Cl
                            ICl                   I
        I


                            Br2                       Br
        II
                                               Br

                                                  OH
         III                   KMnO4

                                                           OH
                                                      H
                            D2/Ni                      D
        IV
                                                       D
                                                      H

   A)   I
   B)   II
   C)   III
   D)   IV
   E)   None of these
        Ans: A

Topic: General Information

   73. The thermodynamic parameters at 298 K for the following reaction are given below.
                                          gas phase
       CH2=CH2 + HCl                                              CH3CH2Cl                     Hº = -64.9 kJ mol-1
       Sº = -131 J K-1 mol-1
       Gº = -25.8 kJ mol-1
       Which of the following statements is true of the reaction?
   A) Both Hº and Sº favor product formation.
    B) Neither Hº nor Sº favors product formation.
    C) The entropy term is unfavorable but the formation of ethyl chloride is favored.
   D) The entropy term is favorable but the formation of ethyl chloride is not favored.
    E) The sign of Gº indicates that the reaction cannot occur as written.
       Ans: C




                                                             271
                                            Chapter 8



Topic: Reaction Products

   74. In general, when the addition of an unsymmetrical electrophilic reagent to an
       unsymmetrical alkene forms the product predicted by Markovnikov's rule, that occurs
       because:
   A) the product is statistically favored.
    B) steric hindrance favors its formation.
    C) it is formed via the more/most stable carbocation.
   D) it is the more/most stable product.
    E) All of the above are reasons.
       Ans: C

Topic: General Information

   75. Which of these compounds belongs to the class of substances commonly known as
       "halohydrins"?
   A) BrCH2CH2Cl
    B) ClCH2CO2H
    C) ICH2CH2OH
   D) FCH2CH2NH2
    E) HOCH2COCl
       Ans: C

Topic: General Information

   76.   Which alkene would you expect to be most reactive toward acid-catalyzed hydration?
   A)    1 pentene
    B)   trans-2-pentene
    C)   cis-2-pentene
   D)    2-methyl-1butene
    E)   All of these would be equally reactive.
         Ans: D

Topic: General Information

   77.   The most resistant compound to the action of hot alkaline KMnO4 is:
   A)    Pentane
    B)   1-Pentene
    C)   2-Pentene
   D)    2-Pentyne
    E)   Cyclopentene
         Ans: A




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                                             Chapter 8



Topic: General Information

   78.   2-Pentyne will not react with:
   A)    H2, Pt
    B)   Br2
    C)   NH3
   D)    H2SO4
    E)   KMnO4/H2O
         Ans: C

Topic: General Information

   79. Consider the ozonolysis products obtained from all the unbranched and unsymmetrical
       isomers of heptene. The reaction product in each case would consist of:
   A) a single aldehyde.
    B) an aldehyde and a ketone.
    C) two different ketones.
   D) two different aldehydes.
    E) a single ketone.
       Ans: D



SHORT ANSWER QUESTIONS

Topic: General Information

   80. The rule that correctly predicts the regiochemistry of most ionic additions to alkenes is
       called ____________________.
       Ans: Markovnikov's Rule

Topic: General Information

   81. When a reaction that could potentially yield two or more constitutional isomers instead
       produces only one as the major product, the reaction is said to be
       _____________________.
       Ans: regioselective

Topic: General Information

   82. When a particular stereoisomer reacts in such a way that it gives a particular
       stereoisomer as a product, even if more than one stereoisomer is theoretically possible,
       the reaction is said to be _____________.
       Ans: stereospecific




                                               273
                                             Chapter 8



Topic: General Information

   83. A reaction in which the reactant is not necessarily chiral but still produces primarily one
       stereoisomeric form of the product (or a specific subset of the possible stereoisomers) is
       referred to as a _________________ reaction.
       Ans: stereoselective

Topic: General Information

   84. Hydroboration-oxidation is a reaction with _________ stereochemistry and
       ________________ regiochemistry.
       Ans: syn, anti-Markovnikov

Topic: General Information

   85. Even when one or more stereogenic centers are produced as the result of an addition
       reaction to an alkene, the product is always formed as a racemic mixture. Why is that?
       Ans: Because alkenes are planar, and the reagent can add from either face.

Topic: General Information

   86. The “decolorization” of molecular bromine is often used as a functional group test to
       detect the presence of ________________.
       Ans: carbon-carbon multiple bonds; or, alkenes and alkynes

Topic: General Information

   87. Neutral divalent carbon compounds are called ___________.
       Ans: carbenes

Topic: General Information

   88. Carbenes are frequently produced by -elimination reactions. These are reactions in
       which the proton being lost and the leaving group are ___________.
       Ans: both attached to the same carbon

Topic: General Information

  89.  bonds are quite susceptible to reaction with electron-seeking reagents, also referred to as
      ____________________.
 Ans: electrophiles




                                               274
                                            Chapter 8



Topic: Reaction Sequence

  90. Predict the final product(s) obtained when (2R,3R)-2-bromo-3-methylpentane is subjected to
      the following sequence of reactions, briefly explaining your rationale. Provide regiochemical
      and stereochemical details as relevant.
          i)      NaOC2H5/C2H5OH, heat
          ii)     BH3, THF
          iii)    H2O2, OH
 Ans: Br H                              H
                       NaOC2H5                       E-3-methyl-2-hexene
         H3C H         C2H5OH              CH3
                                                  Hydroboration/oxidation:
                       (E2: anti
        (2R,3R)                                   overall
                       elimination)
                                                  Anti-Markovnikov,
                                                  syn addition of H2O

                                 H   OH             HO   H

                                               +
                                  H3C H                  H CH3
                                   (2S,3R)             (2R,3S)
                                       3-methyl-2-pentanol
       Heating with sodium ethoxide results in E2 elimination; the anti- elimination leads to
       the formation of E-3-methyl-2-hexene as the major product. Subsequent hydroboration
       oxidation is regioselective (anti-Markovnikov) and stereospecific (syn), resulting in the
       formation of racemic (2S,3R & 2R,3S) 3-methyl-2-pentanol. The other diastereomer
       pair (2S,3S & 2R,3R) is not expected to be obtained.

Topic: Reaction Products

  91. Provide a mechanistic explanation for the following observation: The same major product is
      obtained when 2-ethyl-1-hexene and 3-methyl-2-heptene are allowed to react with HCl.
 Ans:                 HCl

                                                          Cl
                           HCl
                                     most stable
                                     carbocation

       Both alkenes are unsymmetrically substituted: the major product is a consequence of
       regioselective addition to the double bond. Upon reaction with HCl, electrophilic
       addition of a proton results in the formation of the most stable intermediate carbocation,
       which then reacts with Cl, to give the observed product.




                                              275
                                               Chapter 8



Topic: Reaction Products

   92. Predict the major product(s) of the following reaction, giving regiochemical and/or
       stereochemical details as relevant.
                       Br2, H2O
                                          ?

 Ans:
               OH      +             OH
               Br                    Br
              H                     H
        The reaction takes place with Markovnikov regioselectivity and anti stereospecificity,
        giving a racemic mixture of the halohydrin as the major product.

Topic: Reaction Products

  93. Draw Fischer projection formula(s) of the major product(s) of the reaction between Z-2-methyl-
      3-hexene and cold, alkaline KMnO4.
 Ans:                         CH(CH )         CH(CH )
                                        3 2                  3 2

                cold, dil    H     OH         HO         H
                KMnO4        H     OH + HO               H
                                 C2H5               C2H5
        The reaction takes place with syn stereospecificity, giving a racemic mixture of the diol
        product.

Topic: Reaction Products

  94. Draw Fischer projection formula(s) of the major product(s) of the reaction between Z-3-methyl-
      3-hexene and cold, alkaline KMnO4.
 Ans:                            CH2CH3         CH2CH3
                cold, dil H3C      OH      HO      CH3
                             H     OH   + HO       H
                KMnO4
                                   C2H5                  C2H5
        The reaction takes place with syn stereospecificity, giving a racemic mixture of the diol
        product.




                                                   276
                                                     Chapter 8



Topic: Reaction Products

   95. Draw Fischer projection formulas of the major product of the reaction between E-2-methyl-3-
       hexene and aqueous Br2.
  Ans:                        CH(CH )         CH(CH )       CH(CH )          CH(CH )
                                          3 2                       3 2                      3 2                     3 2

                 Br2        HO      H                H         OH              H        Br           Br         H
                              H      Br
                                           + Br                H       + HO             H
                                                                                                 +    H         OH
                 H2O
                                  C2H5                    C2H5                     C2H5                       C2H5
         The reaction takes place with anti stereospecificity. Since the alkene is symmetrically
         substituted, Markovnikov rule is not applicable, and the reaction is not regioselective.
         The product mixture would therefore consist of 2 pairs of enantiomers, that are
         constitutional isomers of each other.

Topic: Reaction Products
   96. Give a mechanistic explanation for the formation of the following product in significant yield.
       What other product(s) might also be obtained? Explain clearly.
                                      HI                                   I



  Ans:
                       H+            +          fast                               I                     I
                                                                   +




                                                                       
                                                 +                  I
                                                                                             I

         The regioselective addition of a proton first generates a secondary carbocation, which
         can undergo rearrangement to a more stable 3o carbocation by two alternate pathways.
         One pathway results in ring expansion to a more stable 5-membered ring. This pathway
         is thus more likely, which would then lead to the observed product. The other pathway
         is less likely, since ring strain is not relieved; however, this could lead to a minor
         product, as shown above.




                                                         277
                                             Chapter 8



Topic: Structure Elucidation

   97. Deduce the structure of an unknown compound A, C8H16, from the following data. Briefly, but
       clearly explain your rationale. A decolorizes Br2/CCl4, and upon reaction with excess H2/Ni,
       affords 1-ethyl-2-methylcyclopentane. When A is subjected to ozonolysis, the following
       product is obtained.

                              O             O


  Ans: A must be 3-ethyl-4-methylcyclopentene. This given data can be explained as shown
       below:
                            C8H14: Index of Hydrogen Deficiency of A = 2

                                       decolorizes Br2,CCl4: A must contain pi bonds

             A             H2, Ni

                                                A must contain some the same carbon
              ozonolysis                        skeleton and one pi bond

              O
                             O             O
        O



            pi bond position in A deduced from the
            structure of the ozonolysis product

Topic: Reaction Products

   98. Predict the product(s) of the oxidation of 2,3,4-trimethyl-1,5-heptadiene with hot, alkaline
       KMnO4.
  Ans:                                                                            OH
                           hot, alkaline CO + H O +                      O +
                                              2     2       O
                           KMnO4                                                O
                                                                      OH




                                                278
                                           Chapter 8



Topic: Reaction Products

  99. Predict the structure of product obtained when cis-2-hexene is allowed to react with Zn/CH2I2.
 Ans:                                               H                       H
                             Zn, CH2I2
                                             H                 + H

       The Zn/CH2I2 produces a carbene which reacts with the alkene to give the
       corresponding cyclopropane derivative. The reaction proceeds with retention of alkene
       stereochemistry, resulting in a racemic mixture of the two cis enantiomers.

Topic: Reaction Products

 100. Predict the structure of product obtained when 1-hexyne is allowed to react with aqueous
      H2SO4 in the presence of catalytic amounts of HgSO4.
 Ans:                   HgSO ,4
                        H2SO4, H2O         OH                          O
       The reaction of 1-hexyne with aqueous H2SO4, in the presence of catalytic amounts of
       HgSO4, results in regioselective hydration to produce an enol, which tautomerizes to the
       more stable keto form.




                                             279

				
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