Deck 5: Stereoisomers

Question 1

Which of the following molecules have the S configuration?

A) I,II
B) I,III
C) III,IV
D) I,II,IV
E) All of the above.

Answer 1

I,II

Question 2

How many stereogenic (chiral)centers are found in Rhizoxin?

A) 5
B) 7
C) 9
D) 11
E) 14

Answer 2

11

Question 3

Which of the following Fischer projections represents (2R,3R)-tartaric acid?

A)

B)

C)

D)

E) None of the above.

Answer 3

Question 4

What (R)or (S)stereochemistry is proper for the following molecule?

A) (2R,3R)
B) (2R,3S)
C) (2S,3S)
D) (2S,3R)
E) None of the above.

Question 5

The meso isomer of 3,4-dibromohexane has what stereochemical configuration?

A) 3R,4S
B) 3R,4R
C) 3S,4S
D) 3S,4R
E) both A and D

Question 6

How many total stereoisomers of the following are possible?

A) 1
B) 2
C) 3
D) 4
E) 6

Question 7

How many total stereoisomers of the following are possible?

A) 1
B) 2
C) 3
D) 4
E) 6

Question 8

How many chiral centers are present in $\beta$ -cadinene?

A) none
B) 1
C) 2
D) 3
E) 4

Question 9

How many total stereoisomers of the following are possible?

A) 1
B) 2
C) 3
D) 4
E) 6

Question 10

(S)-Naproxen,[ $\alpha$ ]_D = + 66 $\degree$ ,is an analgesic (pain reliever),while its enantiomer is toxic.Say that you were given a solution that contains 1 g of Naproxen in 20 mL of liquid,but the optical purity is not specified.You place it in a polarimeter tube (10 cm)and get a reading of + 3.3 $\degree$ from the polarimeter.What is the percent optical purity of the sample?

A) 50
B) 100
C) 0
D) 10
E) 75

Question 11

The correct structure for (R)-bromofluoroiodomethane is:

A)

B)

C)

D)

E)

Question 12

Counting all stereoisomers,how many monochlorinated products of the free-radical chlorination of (R)-2-bromobutane are possible? (Note that the starting compound is one enantiomer only.)

A) 3
B) 4
C) 5
D) 6
E) 8

Question 13

The following molecule has how many possible stereoisomers?

A) 1
B) 4
C) 8
D) 16
E) 32

Question 14

What would be the complete name of the following?

A) (2R,4S)-2-bromopentane
B) (R)-2-bromo-4-methylpentane
C) (S)-4-bromo-2-methylpentane
D) (2R,4R)-2-bromo-4-methylpentane
E) (S)-2-bromo-4-methylpentane

Question 15

Which of the amines below might be appropriate for the resolution of racemic Ibuprofen?

A)

B)

C)

D)

E)

Question 16

The relationship between the following two compounds is:

A) same molecule
B) enantiomers
C) diastereomers
D) mesos
E) conformers

Question 17

A particular reaction produces the following two alcohols in a ratio of 95:5. The enantiomeric excess (% ee)is:

A) 100
B) 95
C) 90
D) 85
E) None of the above.

Question 18

The following two molecules may be described as:

A) constitutional isomers
B) diastereomers
C) enantiomers
D) structural isomers
E) None of the above.

Question 19

Optically pure (S)-monosodium glutamate has a specific rotation of + 24 $\degree$ .What specific rotation would (R)-monosodium glutamate of 50% optical purity have?

A) + 24 $\degree$
B) - 24 $\degree$
C) - 18 $\degree$
D) - 12 $\degree$
E) + 18 $\degree$

Question 20

Which of the following statements is not true?

A) Enantiomers have identical properties except in chiral environments or with plane-polarized light.
B) Reactions involving only achiral or racemic materials must produce achiral or racemic products.
C) Diastereomers have identical properties in all environments.
D) Enantiomers exhibit equal and opposite optical rotations.
E) All of the above are true.

Question 21

The best (most reliable)test for the presence of chirality in a molecule is

A) carbon attached to four different groups.
B) existance of a mirror image.
C) non-superimposability on mirror image.
D) two or more isomers possible.
E) observation of optical rotation in a sample.

Question 22

What technique(s)can be used to obtain non-racemic compounds from racemic material?

A) resolution
B) distillation
C) extraction
D) column chromatography
E) both B and C

Question 23

How are the following compounds related?

A) diastereomers
B) enantiomers
C) meso compounds
D) same compound
E) not related

Question 24

How many stereogenic (chiral)centers are present in the following molecule:

A) none
B) one
C) two
D) three
E) four

Question 25

How are the following compounds related?

A) Diastereomers
B) Enantiomers
C) Meso compounds
D) Same compound
E) They are not related.

Question 26

A graduate student wishes to separate a racemic mixture of acids prepared in the laboratory as shown below.The best way(s)to accomplish this task is:

A) distillation.
B) water solubility.
C) reaction with a chiral amine to form diastereomers,then crystallization.
D) column chromatography.
E) both A and B

Question 27

What is the correct structure for (R)- 4-methyl-2-heptanone?

A)

B)

C)

D)

E)

Question 28

Penicillin V was discovered in the late 1920s by Sir Alexander Fleming in which he won the Nobel Prize for the development of this wonder drug.How many sterogenic centers does penicillin V contain?

A) 1
B) 2
C) 3
D) 4
E) 5

Question 29

Which of the structures below are pairs of enantiomers?

A) (1+2)and (3+4)
B) (1+4)and (2+3)
C) (1+3)and (2+4)
D) All of the above.
E) None of the above.

Question 30

Which of the following molecules represents a meso compound?

A)

B)

C)

D)

E)

Question 31

How would you most accurately describe the relationship between the following two molecules?

A) enantiomers
B) diastereomers
C) meso compounds
D) same compound
E) Both C and D

Question 32

What is the R and S configuration for each stereogenic center of the following sugar from top to bottom?

A) R,S,R
B) S,S,R
C) R,R,S
D) R,R,R
E) S,S,S

Question 33

An unknown compound has been isolated in pure form and found to exhibit [ $\alpha$ ]_D = + 15 $\degree$ (c = 4,CH₂Cl₂).Which of the following might be the structure of the compound?

A)

B)

C)

D)

E)

Question 34

The structure of (-)-geosmin is shown below.Which structure would be that of its enantiomer,(+)-geosmin?

A)

B)

C)

D)

E) None of the above.

Question 35

Sharpless epoxidation of geraniol gave two products,epoxide I (85%)and epoxide II (15%).This mixture of epoxides represents what percent optical purity (or percent enantiomeric excess,% ee)?

A) 0%
B) 15%
C) 70%
D) 85%
E) 100%

Question 36

Which of the structures below are pairs of diastereomers?

A) (1+4)and (2+3)
B) (1+3)and (2+4)
C) (1+2)and (3+4)
D) both A and B
E) both B and C

Question 37

Which of the following is not true for a meso compound:

A) It is achiral.
B) It will rotate plane polarized light.
C) It may be cyclic or acyclic.
D) It is a stereoisomer.
E) It has a mirror plane.

Question 38

Which of the following molecules is not chiral?

A)

B)

C)

D)

E)

Question 39

What would be the proper name of the following?

A) (1R,2R)-trans-1,2-cyclohexanediol
B) (1R,2S)-trans-1,2-cyclohexanediol
C) (1S,2R)-trans-1,2-cyclohexanediol
D) (1S,2S)-trans-1,2-cyclohexanediol
E) (1S,2R)-cis-1,2-cyclohexanediol

Question 40

How are the following compounds related?

A) diastereomers
B) enantiomers
C) meso compounds
D) same compound
E) not related

Question 41

Label the following carbons as either (R)or (S).

A) A = R,B = R,C = R,D = R,E = R
B) A = S,B = S,C = S,D = S,E = S
C) A = S,B = R,C = S,D = S,E = S
D) A = S,B = S,C = R,D = S,E = S
E) A = S,B = S,C = S,D = R,E = S

Question 42

How are the following compounds related?

A) diastereomers
B) enantiomers
C) meso compounds
D) same compound
E) Both meso and the same compound

Question 43

A racemic mixture will rotate light?

A) 0 degrees
B) 180 degrees
C) need more information
D) There is no such thing as a racemic mixture of enantiomers.
E) none of the above

Question 44

How are the following compounds related?

A) diastereomers
B) enantiomers
C) meso compounds
D) same compound
E) They are not related.