Chemistry Department

 

University of Alberta

 

CHEM 263

Final Exam

 

April 16, 2009

 

1. The IR and ¹H NMR spectra of a compound of molecular formula C₆H₁₂O₂ are given below. 

 

SDBSWeb: http://www.aist.go.jp/RIODB/SDBS/ (18-11-08)

 

 

 

 

a.    Calculate the degree of unsaturation. (1 point)

 

b.    List the possible functional groups using the molecular formula and your calculated degree of unsaturation. (2  points)

 

c.    What are the oxygen-containing functional groups listed in your answer to part “b” that the IR spectrum shows to be absent in the unknown?  (1 point)

 

d.    Draw a table that lists chemical shifts and multiplicity.  Then propose a structure for this compound.  (11 points)

 

2. Name five (5) of the following structures: (15 points)

 

1.  

 

 

 

2.  

 

 

3.  

 

 

4.  

 

 

 

5.  

 

 

6.  

 

 

3. Give the structural formula of five (5) of the following compounds. Where given, complete the partial structures: (15 points)

 

1. glycerol

 

2. (R)-2-aminopentanenitrile

 

 

3.  L-serine (as a zwitterion)

 

 

4. cis-3-methylaminocyclohexanecarboxylic acid

 

5. b-D-glucopyranose

 

 

6. (S)-3-ethoxybutanenitrile

 

                       

 

4. Give the structure(s) of the principle organic products of  ten (10) of the following reactions: (30 points)

 

1.  

 

 

2.  

 

 

 

3.  

 

 

 

4.  

 

 

5.  

 

 

6.  

 

 

7.  

 

 

8.  

 

 

9.  

 

 

10.  

 

 

 

11.  

                                                       

           

 

12.  

                       

                                                           

 

5. What reagent(s) would you use to effect ten (10) of the following conversions? (30 points)

 

1.  

                    

                    

2.  

 

3.  

                                                  

                         

4.  

                          

                          

5. 
   

 

6.  

 

7.  

                                                     

 

8.  

 

9.  

 

 

10.  

                                        

 

11.  

                                                                 

 

12.  

                               

 

 

6. Provide synthetic pathways for three (3) of the following transformations (30 points):

 

1.  

 

 

2.  

 

                       

 

3.  

 

 

4.  

                                    

 

7. Pantothenic acid, a B vitamin, is an important intermediate in the synthesis of coenzyme A and can be synthesized from methylpropanal. 

 

a.    Draw the structure of methylpropanal. (3 points)

 

b.    The first step involves the following reaction:

 

 

Draw the product of this crossed aldol reaction. (3 points)

 

c.    Reaction of this product with HCN gives C₆H₁₁NO₂.  Give the structure of this new compound. (3 points)

 

d.    Name the following compound: (3 points)

 

 

e.    Heating the product from part c with aqueous acid gives C₆H₁₂O₄.  Give the structure of this compound. (3 points)

 

f.     Compound C₆H₁₂O₄ reacts to form a g-lactone, C₆H₁₀O₃.  Draw the structure of the lactone. (3 points)

 

g.    The lactone then reacts with H₂NCH₂CH₂CO₂H to give pantothenic acid:

 

 

Using the following structures to represent the lactone and the amine, draw the mechanism of this reaction. (8 points)

 

 

8.  
1. What is meant by the term anomer? (3 points)

 

2. a-D-Mannopyranose reacts with methanol in the presence of a small amount of HCl to give methyl b-D-mannopyranoside according to the following equation.  Propose a mechanism that accounts for this transformation.  (8 points)

 

 

9. Thioesters are compounds in which a sulphur atom has replaced the alkoxy oxygen of an ester.  Acetyl coenzyme A is an important thioester and is central to the following reaction that synthesizes acetylcholine at the nerve synapses:

 

Assuming that choline acetylase is a good source of protons, HB⁺, and of bases to remove protons, B:, write a complete mechanism for this reaction.  Don’t forget to use curved arrows. (12 points)

 

10.  

a.    Explain what is meant by the term essential amino acid. (1 point)

 

b.    Explain the term isoelectric point. (1 point)

 

c.    The isoelectric point of glycine is 6.0.  What is the structure of this acid at pH 10.0? (2 points)

 

d.    Complete hydrolysis of a decapeptide followed by an analysis of the amino acids produced shows that the peptide contains  2 Ala, 1 Arg, 1 Cys, 1 Glu, 1 Gly, 1 Leu, 1 Lys, 1 Phe, and 1 Val fragments.  Edman degradation yields a lysine phenylthiohydantoin.  Partial hydrolysis yields the following peptides:

 

Cys-Glu-Leu

Gly-Arg-Cys

Leu-Ala-Ala

Lys-Val-Phe

Val-Phe-Gly

 

What is the sequence of amino acids in this peptide? (3 points)

 

11. Pentaerythritol, a compound used to make explosives, can be prepared by reacting ethanal with methanal in a basic solution.  The reaction successively yields three compounds of formulae C₃H₆O₂, C₄H₈O₃, and C₅H₁₀O₄.  Compound C₅H₁₀O₄, in the presence of concentrated NaOH, is converted into two compounds, pentaerythritol, C₅H₁₂O₄, and a sodium salt, C₅H₉O₅Na.

 

a.    Give the structure(s) of the principle organic products of the following reactions: (6 points)

 

                      I.         

 

 

                    II.         

 

b.    Draw the mechanism for the formation of compound C₃H₆O₂ via the reaction of ethanal and methanal in a basic solution. (6 points)

 

c.    Draw the structure of pentaerythritol?  (3 points)

 

d.    The Robinson Ring Annulation is a process that fuses a cyclohexanone ring onto a cyclic ketone.  Propose a mechanism for the following example of such an annulation: (12 points)

 

12.  In 1964 Katz obtained a stable dianion, C₈H₆^2-, using butyllithium as the base:

 

           

 

Propose a reasonable structure for the product and explain why it is stable. (6 points)