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					                        ORGANIC CHEMISTRY 30C

                                   (Prof. Gal Bitan)

                               UCLA WINTER 2007

                                    FINAL EXAM
On my honor, I have neither given, nor received, any aide on this exam
(please use ink for this first page!):



       Signature                                                  I.D. number




       Full name (please print!)                                  T.A.

   Notes:
            a) There are no “special” extra credit questions but the total numbe r of points
               is 120.
            b) For all questions, if you are not sure of the final ans wer, show all the steps
               you took to get to the answe r to ensure getting maximum credit. Use the
               back of the page if necessary.

Question                  Points
1 (12)
2 (12)
3 (12)
4 (12)
5 (12)
6 (12)
7 (12)
8 (12)
9 (12)
10 (12)

Total (120)
1. Substance P is an 11-amino acid long neuropeptide that functions as a neurotransmitter and
neuromodulator. Sequence analysis of Substance P has yielded the following results:
       a) Amino acid analysis showed the composition: 1-Arg, 1-Gln, 2-Gly, 1-Leu, 1-Lys, 1-
           Met, 2-Phe, 2-Pro.
       b) It was also found using other techniques that the C-terminus of Substance P, rather
           than being the usual carboxyl groups, COOH, is modified to a carboxamide, CONH2 .
       c) Mass-spectral analysis showed a mass of 1276.6
       d) A first cycle of Edman analysis produced the amino acid lysine.
       e) Cyanogen bromide cleavage yielded one equivalent of methyl thiocya nate and a
           single peptide with a molecular mass 47.2 mass units lower than the untreated one
           (1229.4).
       f) Trypsin digestion yielded the free amino acid lysine and two peptides, whose
           compositions were 1-Arg, 1-Pro; and 1-Gln, 2-Gly, 1-Leu, 1-Met, 2-Phe, 1-Pro,
           respectively. The longer of these two peptides was subjected to two cycles of Edman
           analysis. These cycles revealed the amino acids Pro, and Gly, in this order.
       g) Chymotrypsin digestion yielded the free amino acid phenylalanine and two peptides,
           whose compositions were 1-Arg, 1-Gln, 1-Gly, 1-Lys, 1-Phe, 2-Pro; and 1-Gly, 1-
           Leu, 1-Met, respectively. The shorter of these two peptides was subjected to one
           cycle of Edman analysis, which revealed the amino acids Gly.

Based on this information, what is the primary structure of Substance P?
2. A chemist found two bottles containing colorless compounds hand- labeled
3-methylhexadiene. Because the nomenclature was incomplete, she tested the UV spectrum of
each compound and found that the spectra were different. She labeled the compound that had
maximum absorbance at a shorter wavelength A and the compound with maximum absorbance
at a longer wavelength B. She then did several tests to determine the exact location of the double
bonds in each compound:
        a) Upon reaction with 1 equivalent of HBr at -78°C, compound A gave a 1:1 mixture of
            two products whereas compound B gave a 9:1 mixture of two products.
        b) Upon reaction with 1 equivalent of HBr at 40°C, compound A gave the same 1:1
            mixture of two products whereas compound B gave again a 9:1 mixture of two
            products but this time, the product that was minor at -78°C became the major one and
            the product that was major at -78°C became the minor one.
        c) NMR investigation indicated that upon heating of compound A on its own to 40°C,
            two different sets of peaks appeared, whereas compound B remained unchanged.
        d) Upon heating to 40°C in the presence of maleic anhydride (see reaction below),
            compound A gave no reaction, whereas compound B gave an addition product. The
            chemist wrote the following reaction in her lab book:


                                                                                           O
                                        O


                                                                                               O
           Compound B        +              O


                                                                                           O
                                        O


   A) What are the structures of compounds A and B? (6 points)
   B) What led to formation of two isomers upon heating of compound A alone to 40°C? (6
      points)
3. Suggest a reasonable synthesis of 1-[3-(2-propenyl)-2-hydroxy-5-nitrophenyl)]-1-ethanone
(common name – 3-allyl-2-hydroxy-5-nitroacetophenone) from phenol, using inorganic reagents
and/or organic reagents containing no more than three carbons.
4. Arrange the following compounds in order of increasing acidity:


                                                                          OH




        I                          II                     III        IV
5. Bromobenzene reacts with sodium amide in liquid ammonia to produce aniline. If anthracene
is added to the reaction mixture, a small amount of trypticene also is produced. Write detailed
mechanisms for the reactions that produce aniline and trypticene.




                      trypticene
6. What is the product of a reaction between difluoroethyne and cyclooctatetraene? (6 points)
Show the combination of HOMO and LUMO only for the parts of the two molecules that
participate in the reaction that makes this reaction productive (6 points).
7. Complete the following reactions. Unless stated otherwise, assume room temperature. If
more than one product forms, list all major products (4 points each):



                O
                          1. EtO–/EtOH
                          2. OH–/H2O
A)   2                                        ?
                    O     3. H3O+
                          4. Heat




             NO2

                                           1. H2/Pt
                                           2. HNO2/H2O
B)                                                            ?

                                      CN
                                OH




                                    40ÞC
C)                      + Br2                 ?
8. 1-(N,N-dimethylamino)-1,2-dichloro-1,2-dimethoxyethane has two chiral carbons and
therefore, four diastereomers.

       a) What is the configuration of each chiral center in the isomer below? (4 points)


                                        OMe      Cl
                                 Cl
                                                      OMe


                                  H                   N     CH3

                                                H3C
             1. CH3 I
             2. Ag2 O/H2 O                                  1. H2 O2
             3. heat                                        2. heat



  b) Complete the
  reaction (4 points)                                             c) Complete the
                                                                  reaction (4 points)

Make sure you indicate the stereochemistry of the products in b) and c)!
9. In an article published in January 2007 in the journal Biochemistry, the authors, Siegel et al.,
report that the metabolite 4- hydroxy-2-nonenal may promote aggregation of the amyloid β-
protein, the protein that causes Alzheimer’s disease. The authors suggest that the amino groups
of lysine side-chains react with 4-hydroxy-2-nonenal by 1,2 and/or 1,4 addition.

   a) Write the structure of 4- hydroxy-2-nonenal (4 points).
   b) Write the reactions between the lysine side-chain and 4-hydroxy-2-nonenal leading to 1,2
      and 1,4 addition (4 points).
   c) Would you expect a preference for the 1,2 versus the 1,4 addition? Why? (4 points).
10. In an article published in January 2007 in the Journal of the American Chemical Society, the
authors, Momiyama et al., report a reaction between dienamines (enamines of dienes) and
arylnitroso compounds. Interestingly, although the products look like Diels-Alder products, they
were found to form by a two-step mechanism, in which the first step is an aldol reaction and the
second step is a Michael reaction. Hydolysis of the enamine eventually yields the corresponding
ketone. Show this sequence of reactions, including appropriate reagents, for the following
example:

    O


                           O

    N                      N                                         O
                                                                                    N
                 +
                                                                                O

				
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