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              CH341/CH540, Exam 4 Key, Fall 2009
______________________________________
Name

This exam consists of several parts of unequal difficulty. Look over the whole exam right now, and start
on something you know well. If you don’t know something, skip it, and come back to it later. Use your
time wisely.


              Keep Your Eyes On Your Own Paper!
                                            Grading Summary
         Page 2. _______________ (24)                             Page 5. _______________ (14)


         Page 3. _______________ (24)                             Page 6. _______________ (12)


         Page 4. _______________ (16)                             Page 7. _______________ (10+)




                                      Total _______________ (100)

A Partial Periodic Table of the Elements

1A     IIA    IIIB   IVB   VB   VIB   VII        VIII        IB   IIB   IIIA   IVA    VA     VIA    VII    VIII
                                      B                                                             A       A
1                                                                                                          2
H                                                                                                          He
1.01                                                                                                       4.00
 3     4                                                                5       6     7      8       9     10
Li     Be                                                               B       C     N      O       F     Ne
6.94   9.01                                                             10.8   12.0   14.0   16.0   19.0   20.2
11     12                                                               13     14     15     16     17     18
Na     Mg                                                               Al     Si     P      S      Cl     Ar
23.0   24.3                                                             27.0   28.1   31.0   32.1   35.5   40.0
19     20     21     22    23   24    25    26   27     28   29   30    31     32     33     34     35     36
K      Ca                                                               Ga     Ge     As     Se     Br     Kr
39.1   40.1                                                             69.7   72.6   74.9   79.0   79.9   83.8
37     38     39     40    41   42    43    44   45     46   47   48    49     50     51     52     53     54
                                                                                                     I
                                                                                                    127
                                                                                                         2


1. Give the major organic product of each of the following reactions. If no reaction will occur, write
   “No Reaction”. If a mixture of ortho and para products would form, draw only the para.

a.                  NO2                    HO 3S                  NO2
                               SO3

                            H2SO4

b.                                                                         Br

     H 3C                                        H3C
            CH                       Br2               CH
            CH3                   FeBr3                CH3

c.                                    O                 H3C       O

     H3C    O                   Cl    C

                                       AlCl3
                                                                                 O

d.                                                            O

                                                                      OH
                          1. KMnO4, H2O,
                                                                      OH
                               reflux
                                2. H3O+
                                                              O

e.              O                                                                CH3
                                                MgBr                                OH
     H3C                                                                         C
                            +                                                       CH2CH2CH3
                                                       2. H3O+
                      CH3

f.                         CH3
                           C     CH3
                           Cl                  AlCl3
                                                                  H 3C     CH3
                                                                                                      3


2. Fill in the needed reagents and conditions over the arrows. An arrow may require more than one step.

a.

                O            H2N                                     N


                CH3                H+ (cat.)                         CH3

b.                                                               OCH2CH3
                O
                               2 CH3CH2OH
                                                                     OCH2CH3
                                    +
                                   H (cat.)
                CH3                                                 CH3

c.                                                              OH
                O
                            1. NaCN 2. H2SO4 or                      C     N
                                NaCN/HCN
                CH3                                                  CH3


3. Give IUPAC names for the following structures.

a.

                 CH2CH3
H

    O                         CH3
4-ethyl-7-phenyloctanal

b.
                O
Cl
                      OH
                      CH3
                CH
                CH3
5-chloro-2-isopropylbenzoic acid
                                                                                                                     4


3. Give reasonable arrow-pushing mechanisms for the following reactions. Show all important
resonance forms.

a.
H2N                                               H2N
                           Cl       Cl
                                                                                   + H       Cl
                                   FeCl3
                                                                              Cl


Cl       Cl   AlCl3                        Cl
                                            -



                                                   Cl       AlCl3



H2N                                             H2N                                    H2N


                                                                          H                            H
                           Cl  -




                                                                     Cl                           Cl


H2N
     +




                                           H2N                                         H2N
                                                                      Cl      AlCl 3
                                                                                                       +    H   Cl
                           H                                         H
                                                                                                       Cl
                  Cl                                            Cl

b.
                                                                           O       H
              O                                  H+ (cat.)
                  +        H       OCH3                                            OCH3


                                                      H                                 H
                      H+




              O                                       O +




                                                                                        O


                                                                                   H    OCH3

          O   H                                                      O        H
                               H
              OCH3                                                            OCH3
                               O     CH3
              H
                                                                                                         5


4. Multiple Choice: Choose the best answer for each of the following questions.

1.           In electrophilic substitution reactions, a -Br group is:

             A. Meta directing and activating
D            B. Meta directing and deactivating
_________    C. Ortho-para directing and activating
             D. Ortho-para directing and deactivating
2.        The compound to the right is (was):                                                    NO2
                                                                                                       CH3
            A. A crown ether
B           B. An explosive invented by Alfred Nobel
_________   C. An antimicrobial compound synthesized by Dr. Hathaway                       O2N         NO2
            D. An oxidizing agent
3.        Which reaction is reversible?

            A. Nitration of benzene
C           B. Bromination of benzene
_________   C. Acetal formation
            D. Friedel-Crafts Acylation
4.        Which benzene ring is the least activated towards electrophilic substitution?

             A.                  B.                       C.                   D.
                                                                                       O
D
_________       F                         O               H3C                          N
                                                                                       +




                                  H3C                                         O    -




5.           Which TWO statements are true?

            A. All ortho-para directors are activating groups.
            B. All activating groups are ortho-para directing.
B, E        C. All ortho-para directors are deactivating groups.
_________   D. All deactivating groups are ortho-para directors.
            E. All meta directors are deactivating groups.
            F. All deactivating groups are meta-directors.
6.        Which statement is true about benzene?

                    A.   It is less stable than a hypothetical cyclohexatriene.
D                   B.   It is an equilibrium mixture of two similar structures.
_________           C.   It is the smallest aromatic compound.
                    D.   It is shaped like a regular hexagon.

Draw the                        O
structure of
acetaldehyde.            H3C    C     H
                                                                                                      6


5. Show how you would synthesize the following products from the indicated starting materials, plus
any other reagents.

       Product                                                                  Starting Material
a.
           CH3
       N                                                                              O
H3C    C    CH2CH3                                                             H3C    C    H

                                                                     1. CH3CH2MgBr
           H2NCH3
                                                                         2. H3O+
           H+ (cat.)

           O                                                                     OH
                                         CrO3, H2SO4, H2O
     H3C   C     CH2CH3                                                  H3C     CH CH2CH3




b.
       O
                       I
H3C

                       CH2CH3

                                                                           ClCH2CH3
                 I2/HIO4                                                     AlCl3
       O                                             O
                                              H3C    C      Cl
 H3C
                                                    AlCl3
                        CH2CH3                                                                 CH2CH3
                                                                                                           7


6. What are the four “rules” for an aromatic compound?

       1. Cyclic

       2. Planar (flat) or nearly so

       3. Every ring atom has a p-orbital

       4. 4N + 2 pi-electrons in the system of p-orbitals, (N = 0, 1, 2, 3…)

Classify the following structures as aromatic, anti-aromatic, or non-aromatic. Briefly explain your
reasoning. Don’t merely say, “It follows the rules,” or something similar.

                                                               H
                      N
                                                       H                H



                                                          H            H
Cyclic, flat, p-orbital on each ring atom, but only    Cyclic, flat, p-orbital on each ring atom, and 6
12 electrons in the p-orbitals, so it can’t be         electrons in the p-orbitals, so it is aromatic.
aromatic. 12 is a 4N number, so it is anti-
aromatic.

Bonus! If 1,4-di-tert-butylbenzene is treated with 2-chloro-2-methylpropane and AlCl3, and heated, the
major product is 1,3,5-tri-tert-butylbenzene. Explain how this forms, and why.

                          CH3                   CH3                                   CH3
                             CH3                                                         CH3
                          C            Cl   C    CH3                                  C
                             CH3                                                         CH3
                                                CH3                                             + H       Cl
H3C                                         AlCl3            H3C                          CH3
       C                                                            C                 C
H3C                                                          H3C                        CH3
       CH3                                                          CH3              CH3
The t-butyl group adds ortho to one of the t-butyl groups on the ring. Two t-butyl groups next to each
other causes a lot of steric hindrance, which isn’t good.
                          CH3
                               CH3                                                               CH3
                          C                                                         H                CH3
                                                                                         +       C
                               CH3
                                    + H Cl                                                           CH3
H3C                            CH3                         H3C                         CH3
       C                  C                                        C                C
H3C                            CH3                         H3C                         CH3
       CH3                CH3                                      CH3              CH3
  +
H adds to the ring, and a t-butyl group comes off as a cation.
                                                                                      8


                                                                       CH3
                                                                 H3C      CH3
                                    CH3                                C
                       H               CH3
                             +      C                                       H
                                       CH3
H3C                         CH3
      C                C                                 H3C                    CH3
H3C                         CH3                                 C           C
      CH3              CH3                               H3C                   CH3
                                                                CH3         CH3
The t-butyl group adds meta to minimize the steric hindrance.

				
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