Deck 5: Stereochemistry

Question 1

What term describes the structural relationship between (2R,3R,4S)-2,3,4-trichloroheptane and (2S,3S,5R)-2,3,5-trichloroheptane?

A) not isomers
B) constitutional isomers
C) enantiomers
D) diastereomers
E) conformers

Answer 1

constitutional isomers

Question 2

How many asymmetric carbon atoms are present in the following compound?

A) 0
B) 1
C) 2
D) 3
E) 4

Answer 2

1

Question 3

What is the structural relationship between the two molecule shown below?

A) constitutional isomers
B) enantiomers
C) diastereomers
D) conformational isomers
E) not isomers

Answer 3

constitutional isomers

Question 4

Which of the following terms best describes the pair of compounds shown: $\underline{\text{ enantiomers, diastereomers }}$ , or $\underline{\text{ the same compound? }}$

Question 5

Which of the following $\underline{\text{ incorrectly }}$ describes $\underline{\text{ cis }}$ -1,2-dimethylcyclopentane?

A) It is a meso compound.
B) It is achiral.
C) It contains two asymmetric carbons.
D) Its diastereomer is $\underline{\text{trans }}$ -1,2-dimethylcyclopentane.
E) It has an enantiomer.

Question 6

How many enantiomers are there of the molecule shown below?

A) 0
B) 1
C) 2
D) 3
E) 6

Question 7

What term describes the structural relationship between (2R,3R,4S)-2,3,4-trichloroheptane and (2S,3S,4R)-2,3,4-trichloroheptane?

A) not isomers
B) constitutional isomers
C) enantiomers
D) diastereomers
E) conformers

Question 8

How many asymmetric carbon atoms are present in the molecule shown?

A) 0
B) 1
C) 2
D) 3
E) 4

Question 9

Is the molecule shown below chiral or achiral?
(CH₃)₃CCH(CH₃)₂

Question 10

How many asymmetric carbons are present in the compound below?

Question 11

How many asymmetric carbon atoms are present in the molecule shown?

A) 0
B) 1
C) 2
D) 3
E) 4

Question 12

How many asymmetric carbons are present in the compound below?

Question 13

________ are isomers which have the same bonding sequence but differ in the orientation of their atoms in space.

Question 14

Which of the following terms best describes the pair of compounds shown: $\underline{\text{ enantiomers, diastereomers }}$ , or $\underline{\text{ the same compound? }}$

Question 15

How many asymmetric carbon atoms are present in the molecule shown?

A) 0
B) 1
C) 2
D) 3
E) 4

Question 16

What term describes the structural relationship between $\underline{\text{ cis }}$ -1,2-dimethylcyclopentane and trans-1,3-dimethylcyclopentane?

A) not isomers
B) constitutional isomers
C) enantiomers
D) diastereomers
E) conformers

Question 17

How many asymmetric carbons are present in the compound below?

Question 18

How many asymmetric carbon atoms are present in the molecule shown?

A) 0
B) 1
C) 2
D) 3
E) 4

Question 19

Which of the following terms best describes the pair of compounds shown: $\underline{\text{ enantiomers, diastereomers }}$ , or $\underline{\text{ the same compound? }}$

Question 20

How many asymmetric carbon atoms are present in the following compound?

A) 0
B) 1
C) 2
D) 3
E) 4

Question 21

Is the molecule shown below chiral or achiral?
CH₃CH₂CH(CH₃)CH₂CH₃

Question 22

Is the molecule shown below chiral or achiral?

Question 23

How many asymmetric carbons are present in the compound below?

Question 24

If possible, draw the structure of the enantiomer of the molecule shown below.

Question 25

Is the molecule shown below chiral or achiral?

Question 26

Which of the following terms best describes the pair of compounds shown: $\underline{\text{ enantiomers, diastereomers }}$ , or $\underline{\text{ the same compound? }}$

Question 27

Which of the statements below correctly describes an achiral molecule?

A) The molecule has a nonsuperimposable mirror image.
B) The molecule exhibits optical activity when it interacts with plane-polarized light.
C) The molecule has an enantiomer.
D) The molecule might be a meso form.
E) None of the above

Question 28

Is the molecule shown below chiral or achiral?

Question 29

Circle each chiral molecule among those shown below.

Question 30

Is the molecule shown below chiral or achiral?

Question 31

Is the molecule shown below chiral or achiral?

Question 32

Is the molecule shown below chiral or achiral?

Question 33

Which of the following terms best describes the pair of compounds shown: $\underline{\text{ enantiomers, diastereomers }}$ , or $\underline{\text{ the same compound? }}$

Question 34

Circle all structures shown below that are chiral.

Question 35

Is the molecule shown below chiral or achiral?

Question 36

Is the mirror image of the following molecule an enantiomer or is it superimposable with it?

Question 37

Draw the enantiomer of the molecule shown below.

Question 38

Circle each chiral molecule among those shown below.

Question 39

Is the molecule shown below chiral or achiral?

Question 40

How many asymmetric carbons are present in the compound below?
3-ethyl-2,2,4-trimethylpentane

Question 41

Draw the structure of (2R,3S)-2,3-dichloropentane. Take particular care to indicate three-dimensional stereochemical detail properly.

Question 42

Label each asymmetric carbon in the compound below as R or S.

Question 43

Draw the Fischer projection of (S)-2-bromobutane.

Question 44

Assign the proper configurational label, R or S, to the chiral carbon in the molecule shown below.

Question 45

Draw the structure of (S)-3-chloro-3-methylhexane. Take particular care to indicate stereochemistry properly.

Question 46

Assign the proper configurational label, R or S, to each chiral carbon in the molecule below.

Question 47

Label each asymmetric carbon in the compound below as R or S.

Question 48

Which of the following structures are achiral and meso?

A) 1, 2, 3 & 4
B) 1 &2
C) 2 & 3
D) 1 & 4

Question 49

Label each asymmetric carbon in the compound below as R or S.

Question 50

Draw the structure of (1R, 2R)-1-bromo-2-chlorocyclobutane. Take particular care to indicate stereochemistry properly.

Question 51

Label each asymmetric carbon in the molecule below as having the R or S configuration.

Question 52

How many asymmetric carbons are present in the compound below?

Question 53

Draw the structure of the enantiomer of (2S, 3R)-2,3-dichloropentane. Take particular care to indicate three-dimensional stereochemical detail properly.

Question 54

Draw the structure of any diastereomer of (2S, 3R)-2,3-dichloropentane. Take particular care to indicate three-dimensional stereochemical detail properly.

Question 55

Draw the structure of (S)-1-bromo-1-chloropropane. Take particular care to indicate three-dimensional stereochemical detail properly.

Question 56

Draw the structure of (2R,3R)-2,3-dibromo-3-chloropentane.

Question 57

Does the molecule shown below contain asymmetric carbon atoms? Is this molecule chiral?

Question 58

Label each asymmetric carbon in the compound below as R or S.

Question 59

Draw the structure of (1R, 2S, 3S)-1,2-dibromo-3-ethylcyclohexane. Take particular care to indicate stereochemistry properly.

Question 60

Label each asymmetric carbon in the compound below as R or S.

Question 61

If a mixture contains 75% of one compound and 25% of its enantiomer, what is the e.e. of the mixture?

A) 100
B) 75
C) 50
D) 25
E) 3

Question 62

Label each asymmetric carbon in the compound below as R or S.

Question 63

Can one predict whether a compound with a single asymmetric carbon is dextro- or levorotatory based on the R/S assignment at this asymmetric carbon? Explain briefly.

Question 64

Given that glucose has a specific rotation of +52.8°. Predict the concentration of a glucose aqueous solution contained in a 10 cm long polarimetry tube if a rotation of +15.8° was observed.

A) 0.299 g/mL
B) 0299 g/mL
C) 3.34 g/mL
D) 334 g/mL

Question 65

A mixture of equal amounts of two enantiomers ________.

A) is called a racemic mixture
B) is optically inactive
C) implies that the enantiomers are meso forms
D) both A and B
E) none of the above

Question 66

Which of the following statements correctly pertains to a pair of enantiomers?

A) They rotate the plane of polarized light by exactly the same amount and in opposite directions.
B) They rotate the plane of polarized light by differing amounts and in opposite directions.
C) They rotate the plane of polarized light by differing amounts and in the same direction.
D) The have different melting points.
E) They have the same melting point, but they have different boiling points.

Question 67

Which of the following statements is (are) true for the compound (R)-2-butanol?

A) This compound is chiral.
B) This compound is optically active.
C) This compound has an enantiomer.
D) all of the above
E) none of the above

Question 68

A mixture of two enantiomers with a composition of 65.0% R has an observed rotation of -25.3° in a polarimeter tube. If the mixture has a concentration of 2.038 g/mL at 25°C, what is the predicted [α]²⁵D of an optically pure sample of the S enantiomer?

A) -25.3°
B) -53.5°
C) +12.4°
D) +41.3°
E) +53.5°

Question 69

A student measured the optical activity of an unknown sugar at two different concentrations. The results of his measurements are shown below. Given that the sample cell had a path length of 10.0 cm, calculate the specific rotation for the unknown sugar. (Hint: Consider each measurement of plane polarized light has a true reading and a "ghost" reading 180° from the true reading).

A) -10.5^∘
B) +25.6^∘
C) +79.5^∘
D) -105^∘
E) +256^∘

Question 70

Compounds that rotate the plane of polarized light clockwise are called ________.

Question 71

Would a 50:50 mixture of (2R,3R)-2,3-dibromobutane and (2R,3S)-2,3-dibromobutane be optically active? Explain.

Question 72

Which of the following configurations corresponds to the structure below?

A) (4R, 5R)
B) (4R, 5S)
C) (4S, 5R)
D) (4S, 5S)

Question 73

If (S)-glyceraldehyde has a specific rotation of -8.7°, what is the specific rotation of (R)-glyceraldehyde?

A) 0.0°
B) -8.7°
C) +8.7°
D) cannot be determined from the information given

Question 74

Captopril is used to treat high blood pressure and congestive heart failure. Label the chiral centers as R or S.

Question 75

For the structure shown below, draw the stereoisomer having a configuration of (1R,3S,4S) in a perspective structure.

Question 76

Predict the specific rotation of the compound shown.

A) It is impossible to predict; it must be determined experimentally.
B) Because both asymmetric centers are R, the compound is dextrorotatory.
C) Because both asymmetric centers are S, the compound is levorotatory.
D) Zero; the compound is achiral.
E) Because this compound represents a racemic mixture, the compound is dextrorotatory.

Question 77

Label each asymmetric carbon in the compound below as R or S.

Question 78

A newly isolated natural product was shown to be optically active. If a solution of 2.0 g in 10 mL of ethanol in a 50 cm tube gives a rotation of +2.57°, what is the specific rotation of this natural product?

Question 79

Calculate the e.e. of a mixture containing 8.0 g of (-)-glyceraldehyde and 2.0 g of (+)-glyceraldehyde.

Question 80

Phantasmidine, shown below, is found in poisonous frog skin and has analgesic properties (J. Nat. Prod. $\textbf{ 2010, }$ 331). Assign each chiral center as having either R or S configuration.