Name:_____________________________________ W (Print your name clearly!)

Sametz: CHEM 321 Fall 2012

Organic Chemistry Final All answers should be written CLEARLY in the space provided. (If it’s not clear, it’s wrong).

You may raise your hand to ask a question if you are unsure what a question is asking of you.

1. (4 points) Give a proper IUPAC name for the following compound:

2. (4 points) Draw the structure of (1R, 2R)-1,2-cyclobutanediol.

3. (6 points) Rank the following compounds on order of increasing basicity (1 = most basic, 7 = least).

4. (11 points) Draw all possible isomers of C5H11Br, including stereoisomers. Label any stereogenic centers on your structures with an asterisk (*). Note: points will be deducted for incorrect or redundant structures. 5. (4 points) Explain why methane and tetrachloromethane are nonpolar molecules, but dichloromethane is polar.

6. Compound A reacts with base to give epoxide B, whereas compound C (a diastereomer of A) reacts under the same conditions to give D instead.

a) (12 points) Give mechanisms for both reactions, and explain why the two diastereomers react differently. Hint: cyclohexanes!

6b) (4 points) Actually, compound D on the previous page is not the final product. Under the reaction conditions, it is in equilibrium with another, highly favoured, form. Draw the structure of the major form, and give a mechanism for its formation under these basic conditions. 7. (8 points) For each of the following pairs of structures, indicate if they represent a pair of diastereomers, enantiomers, constitutional isomers, or identical compounds. a)

b)

c)

d)

8. For the compound shown below:

a) (1 point) What is the name for this class of compounds (i.e. 1,2-dienes)? __________________ b) (4 points) Draw a 3-dimensional representation of this structure that reflects its geometry. On

this structure, show how the p-orbitals overlap to form -bonds. c) (3 points) Indicate the hybridization of each carbon atom on the molecule. d) (2 points) Explain why the molecule is chiral.

9. For reactions where more than one product is possible: a) (2 points) What is meant by the “thermodynamic product”? b) (2 points) What is meant by the “kinetic product”? c) (3 points) Give three ways to encourage formation of a kinetic product over formation of a competing thermodynamic product. 10. (8 points) An unknown compound containing only carbon and hydrogen, in contact with a platinum catalyst, reacts with 3 equivalents of hydrogen gas to give 1-isopropyl-4-methylcyclohexane. When the unknown compound is treated with ozone followed by dimethylsulfide, the following products are obtained:

What is the structure of the unknown product? The structure of 1-isopropyl-4-methylcyclohexane is worth partial credit.

11. (28 points) Give the major organic product(s) for the following reactions, including stereochemistry if applicable. a)

b)

c)

d)

e)

f)

g)

12. (18 points) Provide reagents that will effect the following transformations: a)

b)

c)

d)

e)

f)

13. (16 points) Reaction mechanisms (8 points): Show a reasonable reaction mechanism for TWO of the following three reactions. If you show work on more than two, CLEARLY indicate which ones you wish to count for credit; otherwise, the grader will choose the first two. a)

b)

c)

(Extra space for question 13)

14. (4 points) Multistep Synthesis: Choose ONE of the two following two synthesis problems below. Show how you can make the final product from the given starting material. The syntheses will require more than one chemical step. Retrosynthetic analysis is worth part credit, but for full credit write out the forward sequence of reactions with specific reagents. Mechanisms are not required and are not graded. If you show work on more than one problem, CLEARLY indicate which you want graded; otherwise the first on the page, as judged by the grader, will count for credit. a)

b)

15. (6 points) Multistep Synthesis: Choose ONE of the two following two synthesis problems below. Show how you can make the final product from the given starting material. The syntheses will require more than one chemical step. Retrosynthetic analysis is worth part credit, but for full credit write out the forward sequence of reactions with specific reagents. Mechanisms are not required and are not graded. If you show work on more than one problem, CLEARLY indicate which you want graded; otherwise the first on the page, as judged by the grader, will count for credit.

a)

b)

EXTRA CREDIT: 20 points. The following questions involve the chemistry of phenylethylamines, a class of compounds known for their stimulant and psychoactive effects. 16. The structures of ephedrine and pseudoephedrine are shown below. Only the commercially-used enantiomer of each shown below. Ephedrine is a bronchodilator, and has also been used as a stimulant and weight-loss aid. Pseudoephedrine has found use as a decongestant, but in recent years has been phased out. Both have been used as precursors in the illicit synthesis of methamphetamine, and are controlled substances

a) (4 points) Label each stereocenter in the above structures with their correct IUPAC stereochemical descriptor (R or S). b) (4 points) Redraw the structures above as Fischer projections, using the templates below:

17. Not all methamphetamine is treated the same by law. The d-enantiomer (dextromethamphetamine) is a stimulant and psychoactive drug, and a Schedule II controlled substance. The l-enantiomer (levomethamphetamine) is a vasoconstrictor, and is an ingredient in over-the-counter medications such as Vicks VapoInhaler®. The “street drug” may either be a racemate, or pure dextromethamphetamine, depending on the manner of production.

a) (4 points) If d-methamphetamine is also the S-isomer, then draw the structure of levomethamphetamine with the correct stereochemistry. b) (2 points) Is the illicit enantiomer (-)-methamphetamine, or (+)-methamphetamine?

18. (6 points) Epinephrine (adrenaline) and norepinephrine (noradrenaline) are hormones and neurotransmitters. You are probably familiar with adrenaline for its involvement in the “fight or flight” response to stress or fear. The biosynthesis of these compounds involves conversion of tyrosine (an amino acid) to L-DOPA (used to treat Parkinson’s disease), then to dopamine (which is involved in reward-seeking and addictive behaviors), then norepinephrine. The final step of the biosynthesis of epinephrine is shown below:

Give an arrow-pushing mechanism for this reaction. You may abbreviate the above chemical structures using generic groups such as R, as long as your answer is clear.