CHEMISTRY 211 EXAM 3 Friday, November 5, 2004

Name . Hold .

Answer all 14 questions (150 pts).

1. (14) Designate either R or S to each of the following molecules. You must show the priorities (#1 = highest) of all 4 attached groups (in each case) to receive full credit.

a) b) 2 3 HN CH2Cl 2 CH2OH O Br 1 (S) 4 (R) NH2 4 1 O 3

2. (8) Name the following molecule using IUPAC rules. Do not assign E or Z.

2 4 8 F 7 1-fluoro-3,5-dimethyl-1-octen-6-yne 3 5 6 1

3. (3) True or False? The pKa of a proton attached to the C of a terminal alkyne is less acidic than that of water.

4. (3) True or False? A meso compound must have a superimposable mirror image.

5. (10) (Z) 9-Tricosene is the sex pheromone of the female housefly. Write a synthesis of (Z) 9- tricosene using acetylene and any necessary organic or inorganic reagents.

H H

CH (CH ) (CH ) CH (Z) 9-Tricosene acetylene 3 2 7 2 12 3

1 eq. NaNH2

H2 Lindlar's catalyst CH3(CH2)7Br

1 eq. NaNH2 CH3(CH2)12Br CH3(CH2)7- H CH3(CH2)7- (CH2)12CH3

6. (10) In part a) only, draw the consequence of the arrows shown. Examine the resulting 2 resonance forms and circle the one which would be the greater contributor to the overall resonance hybrid. In part b) only, draw the arrow(s) which would lead to the resonance form on the right. a) OH OH b) N N

7. (7.5) For the following questions match each definition to a term from the list below. A. racemic mixture B. constitutional isomers C. chirality D. diastereomer E. enantiomer F. meso compound

a) enantiomer a stereoisomer which is not superimposable on its mirror image.

b) diastereomer a stereoisomer which is not an enantiomer.

c) meso compound an achiral compound with more than 1 chiral center .

8. (42) In each of the following reactions, reactants, products or simple statements are missing. Fill in the blanks with the appropriate molecules or answers. If more than one reaction step is involved, indicate this by using 1)...... ; 2)...... Show product stereochemistry, as appropriate. a) 2 HBr Br Br b) O HgSO4 + H3O O c) KMnO4 HO + OH H3O O

HCl OH Cl

H H e) excess H2 / Pd

H3C H3C H H f) Et2CuLi

Cl g) Br NBS +

9. (7.5) Fill in the blanks: Unlike alkenes or alkanes, a hydrogen attached to the carbon of an alkyne triple bond can be abstracted using a base which is stronger (stronger / weaker) than the conjugate base of the alkyne. The approximate pKa of an alkyne proton is 25 and it is more acidic than an alkene because the resultant anion is more (more / less) stable than that from the alkene.

10. (9) For each pair indicated below, indicate by yes or no whether or not they represent resonance forms.

• Yes

• No

• Yes

N O N O • No

c) • Yes

N C S S C N • No

11. (18) For each of the following pairs, circle all of the statements to their right which are correct.

CH OH CH OH

2 2 • mirror images

• enantiomers

HO H H OH

• identical

and

• meso

HO H H OH

• stereoisomers

• diastereomers

CH OH CH OH

2 2

Br • mirror images Br

• enantiomers

H CH H C H 3 3 • identical

and

• meso

H CH CH CH CH • diastereomers H 2 3 3 2

Cl Cl

• mirror images

• enantiomers H C F

• identical

and H N CH

2 3

• meso

• diastereomers HOH C NH

2 2 CH OH

12. (8) By analogy with what you have seen before, show likely products for each of the following reactions:

D D D 2

H C C C CH CH

3 2 3

Lindlar's catalyst

[Note: D = deuterium, an isotope of H]

H b)

1) NaNH 1 eq. 2 H3C C C Si CH3 H C C C H

H 2) H

H C Si Br

13. (7) In principle, how many different, mono-bromo products could be formed from the reaction shown below? In practice, only one product is formed, draw this major product.

Br 2 3 products, CH 2 C Br major

light in principle H2

14. (3) Which Fischer projection is the same as the molecule in the box?

CH3 NH2 COOH NH2 NH2 C H NH H HOOC CH3 2 CH3 COOH COOH H CH3 H (A) (B) (C)