Recitation

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					                                                           Chapter 22 Recitation

Please note that these exercises are not a substitute for but an addition to the homework
assignment
1. Give the hybridizations of the orbitals on the numbered carbon atoms in the following molecules and
   give the bond angles for the bonds around them. Which one(s) exhibit(s) cis-trans isomerism?



        H             H                                H


H       C             C3           H            H      C        C          C   CH3      H3C      C      C       H
                                                                 2                                       1
        H             H
                                                       H        H          H
             (A)                                                (B)                               (C)

C1     sp3           109 º

C2     sp2        120 º

C3     sp         190 º



2. Peroxypropionyl nitrate (PPN) is an eye irritant found in smog. Give the hybridizations of the orbitals on
   the numbered atoms in its structure and the bond angles. The octet rule is obeyed.


              H            O                               O
                               5

H3C          C             C           O        O          N          O
                 6          4              3                2          1

             H

O1 ,     N2          O3         and        C6       are sp3 hybridized and the bond angles around them are 109 º .

C4 and O5 are sp2 hybridized and the bond angles around them are 120 º .
3. Give the structural formulas of
       a. the three-carbon alcohol with an OH group at the end of the chain.


      H
            H     H

H     C     C     C     OH

      H     H     H

       b. the three-carbon carboxylic acid.

      H
            H

H     C     C     C     OH

      H     H
                  O

       c. the ester formed when these two compounds react.

      H
            H                    H     H         H

H    C      C     C      O       C      C        C      H

     H      H                    H      H
                  O                              H

4. Draw and name all the structural isomers of dichroropropane (C3H6Cl2).


      H
            H     H

H    C      C     C      Cl

     H
            Cl   H
1,2-dichloropropane
                                                                        H
                                                                            H   H

                                                                    H   C   C   C    Cl

                                                                        H   H
                                                                                Cl
                                              1,1-dichloropropane
                                      H
                                              Cl       H

                             H        C       C        C            H

                                      H
                                              Cl       H
2,2-dichloropropane




                                 H
                                          H        H

                         H       C        C        C           Cl

                                 Cl       H
1,3-dichloropropane                                H

5. Draw and name all the isomers of dichloroethene (C2H2Cl2).

H               Cl                                Cl                                           Cl
                                                                            Cl                                 H
    C      C                                           C            C                               C    C
H              Cl                                  H                    H                       H            Cl

1,1-dichloroethene                                 cis-dichloroethene                         tran-dichloroethene


6. Each of the following names is wrong. Draw structures based on these names then give the correct
   names.
                                   H     H   H      H     H
                                                                H
                                 H        C        C       C            C        C   C    H
                                          H        H       H        CH3          H   H
    (a) 4-methylhexane                                                                        3-methylhexane

                                 H        H       H        H        H

                      H          C        C    C           C        C        H
                                 H        H    H                    H
                                                       C2H5
                                                                                     3-methylhexane
    (b) 2-ethylpentane
                                    CH3




    (c) 2-methylcyclohexane                   methylcyclohexane




                                             CH3

                                    CH3 CH2 C CH CH2CH2 CH2 CH3


                                            CH3C2H5
    (d) 3,3-methyl-4-ethyloctane                                        4-ethyl-3,3-dimethyloctane

7. Draw structures from the following names, and determine which compounds are optically active. An
   optically active compound has a structure that is not super-imposable with the structure of a compound
   that is a mirror image of it. An organic compound containing on or more C atoms with sp3 and attached
   to four different atoms or groups of atoms exhibits optical isomerism.

    (a) 3-bromohexane

    (b) 3-chloro-3-methylpentane

    (c) 1,2-dibromo-2-methylbutane.

Ignore this question as you have not taken optical activity in organic compounds although I give the answer
   below.



       H    H      H      H     H     H

H      C    C      C      C     C     C       H
                          H
      H     H                   H      H
                  Br
                                                 This compound is optically active. The hybridization
    of the third C from the left is sp3 and four different groups are attached to it. These are H, Br,
    C2H5 and C3H7.
           H     H     CH3     H        H

H          C     C     C       C        C    H
                               H
           H     H                      H
                       Cl
                                                 This compound is not optically active. There is no C with four
     different groups attached to it.



       H         CH3 H         H

H      C         C    C        C       H
                               H
       Br        Br   H
                                  This compound is optically active. The second C from the left is
     attached to four different groups. These are CH2Br, Br, CH3 and C2H5.



8. Which of the following structures exhibit geometric isomerism? Draw and name the two isomers in
   each case.

     (a)
               CH3     CH2             CH     CH          CH3

CH3                            CH3                 C2H5
                      H
      C          C                     C     C
 H                    C2H5         H              H

      Trans isomer                      Cis isomer


     (b)

                          CH       CH        CH3


CH3
                      H                       H                 H
      C          C                                 C       C
 H
                                              CH3



Trans isomer                                Cis isomer
      (c)
                        CH3
                                                 CH3

            CH3         CH  C    CH         CH2      CH3
This compound does not exhibit cis-trans isomerism as one of the C atoms on the double bond has two
   identical groups (CH3 groups) on it.


9. Which compounds exhibit geometric isomerism? Draw and name the two isomers in each case.

      (a) propene                   (b) 3-hexene        (c) 1,1-dichloroethene          (d) 1,2-dichloroethene

      CH3
                                 H
                C       C
       H                        H does not exhibit cis-trans isomerism. Two H's on the same C atom.
(a)

            H                    C2H5              C2H5                  C2H5
                C           C                              C         C
      C2H5                      H                      H                  H
(b)
                    Trans                                      Cis

      Cl                        H
             C         C
        Cl                  H Does not exhibit cis-trans isomerism each C is bonded to two identical atoms
(c)

        Cl                       H                 H                     H
                C           C                           C            C
            H                    Cl                Cl                     Cl
(d)
                    Trans                                    Cis

10. Write down the structures of the primary, secondary and tertiary isomers of the amine C4H9NH2.

                                                                                                                 NH2
                                                                                        NH2
CH3              CH2            CH2        CH2         NH2               CH3     CH2    CH     CH3    CH3              CH3
                                                                                                                 C

                                                                                                                 CH3
                       Primary                                                  secondary                   tertiary
11. What product is formed by:

   (a) The oxidation of a primary alcohol such as C2H5OH.
               O
       CH3C
                H

   (b) The oxidation of the seconday propyl alcohol. CH3CH(OH)CH3.

       CH3       C      CH3

                 O

   (c) The oxidation of acetaldehyde CH3CHO.

                     OH
     CH3        C

                O

   (d) The reaction between methyl alcohol CH3OH and acetic acid CH3COOH.


                     OCH3
     CH3        C

                O

12. Which of the following will undergo an addition reaction?

   (a) alkene        (b) alkane      (c) benzene       (d) an alcohol

13. Familiarize yourself with the two main ways of obtaining polymers. Addition polymerization is a chain
    reaction initiated by a free radical. Elimination reaction involves the removal a small molecule from
    two molecules for each extension of the chain. When such molecule is water as is commonly the case
    elimination reactions are referred to as condensation reactions. Many elimination polymers are called
    Polymers are called polyesters because the repeating unit is an ester formed by eliminating water from
    an alcohol and a carboxylic acid. Familiarize yourself with the many uses of polymers.

				
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