Organic Chemistry

234 CHAPTER 5 Stereochemistry

58. a. Give the product(s) that would be obtained from the reaction of cis-2-butene and trans-2-butene with each of the following
    reagents. If the products can exist as stereoisomers, show which stereoisomers are obtained.
    
    
    1. HCl 5.
    
    
    2. followed by 6.
    
    
    3. 
       
       
       
       7. 
          
       
       
       
       
    
    
    4. in 8.
       b. With which reagents do the two alkenes react to give different products?
    
    
    
    


59. Which of the following compounds have an achiral stereoisomer?
    a. 2,3-dichlorobutane f. 2,4-dibromopentane
    b. 2,3-dichloropentane g. 2,3-dibromopentane
    c. 2,3-dichloro-2,3-dimethylbutane h. 1,4-dimethylcyclohexane
    d. 1,3-dichlorocyclopentane i. 1,2-dimethylcyclopentane
    e. 1,3-dibromocyclobutane j. 1,2-dimethylcyclobutane


60. Give the products and their configurations obtained from the reaction of 1-ethylcyclohexene with the following reagents:

a. HBr d. followed by

b. e.

c.

61. Citrate synthase, one of the enzymes in the series of enzyme-catalyzed reactions known as the Krebs cycle, catalyzes the synthesis
    of citric acid from oxaloacetic acid and acetyl-CoA. If the synthesis is carried out with acetyl-CoA that has radioactive carbon
    in the indicated position, the isomer shown here is obtained.

a. Which stereoisomer of citric acid is synthesized,Ror S?

b. Why is the other stereoisomer not obtained?

c. If the acetyl-CoA used in the synthesis does not contain will the product of the reaction be chiral or achiral?

62. Give the products of the following reactions. If the products can exist as stereoisomers, show which stereoisomers are obtained.

a. f.

b. g.

c. h.

d. i.

e. j.

63. The specific rotation of (R)- -glyceraldehyde is If the observed specific rotation of a mixture of (R)-glyceraldehyde and
    (S)-glyceraldehyde is what percent of glyceraldehyde is present as the Renantiomer?


64. Indicate whether each of the following structures is (R)-2-chlorobutane or (S)-2-chlorobutane. (Use models, if necessary.)

a. c. e.

b. d. f.

65. A solution of an unknown compound (3.0 g of the compound in 20 mL of solution), when placed in a polarimeter tube 2.0 dm
    long, was found to rotate the plane of polarized light 1.8°in a counterclockwise direction. What is the specific rotation of the
    compound?

Cl

C

CH 3

H

Cl CH 2 CH 3

H

H

CH 3

CH 3

H

H Cl

Cl

CH 3

HCl

CH 2 CH 3

H

H

Cl

H

H 3 C

H CH 3

+1.4°,

(+) +8.7°.

1,2-dimethylcyclohexene+HCl 1-chloro-2-ethylcyclohexene+H 2 ,Pt>C

1,2-diethylcyclohexene+H 3 O+ (Z)-3,4-dimethyl-3-heptene+H 2 ,Pt>C

1-ethylcyclohexene+H 3 O+ (E)-3,4-dimethyl-3-heptene+H 2 ,Pt>C

trans-2-pentene+HCl 3,3-dimethyl-1-pentene+Br 2 >CH 2 Cl 2

cis-2-pentene+HCl 1,2-dideuteriocyclohexene+H 2 ,Pt>C

(^14) C,
CH 2 COOH
CH 2 COOH
14
COOH
CH 3 CSCoA C
14
HO
citrate synthase
O
HOOCCH 2 CCOOH
O

• oxaloacetic acid acetyl-CoA
  citric acid
  (^14 C)
  H 2 ,Pt>C
  HBr+peroxide Br 2 >CH 2 Cl 2
  BH 3 >THF HO-,H 2 O 2
  Br 2 CH 2 Cl 2 HCl+CH 3 OH
  HBr+peroxide HCl+H 2 O
  BH 3 >THF HO-,H 2 O 2 H 2 >Pt>C
  Br 2 +H 2 O