Deck 7: Chirality

Question 1

Which of the following molecules are chiral?

A) only II
B) only III
C) II and III
D) I, II, and III

Answer 1

only II

Question 2

How many stereogenic centers are there in the following molecule?

A) only 1
B) two
C) three
D) four

Answer 2

two

Question 3

What is the IUPAC name of the following compound?

A) (2S, 3S)-2,3-dibromopentane
B) (2S, 3R)-2,3-dibromopentane
C) (2R, 3S)-2,3-dibromopentane
D) (2R, 3R)-2,3-dibromopentane

Answer 3

(2R, 3R)-2,3-dibromopentane

Question 4

What is the relationship between the following two molecules?

A) identical
B) enantiomers
C) diastereomers
D) constitutional isomers

Question 5

What are the configurations of carbons 2 and 3 in the Fischer projection below?

A) 2R, 3R
B) $2 \mathrm{R}, 3 \mathrm{~S}$
C) 2S, 3R
D) 2S, 3S

Question 6

Compound $\mathrm{X}, \mathrm{C}_{5} \mathrm{H}_{10} \mathrm{O}$ , is optically active. The compound consumes one equivalent of hydrogen to give $\mathrm{C}_{5} \mathrm{H}_{12} \mathrm{O}$ . The hydrogenation product is also optically active. Which compound below matches the information?

A)

B)

C)

D)

Question 7

A pure sample of (S)-phenylalanine has a specific rotation of $+70^{\circ}$ . A mixture of the two enantiomers of phenylalanine has a specific rotation of $+7.0^{\circ}$ . What are the percentages of the $S$ and $R$ enantiomers in the mixture?

A) $95 \% \mathrm{~S}, 5 \% \mathrm{R}$
B) $90 \% \mathrm{~S}, 10 \% \mathrm{R}$
C) $55 \% \mathrm{~S}, 45 \% \mathrm{R}$
D) $52.5 \% \mathrm{~S}, 47.5 \% \mathrm{R}$

Question 8

Which of the following has a meso stereoisomer?
I. 2,4-dichloropentane
II. 1,3-dimethylcyclopentane
III. 2,3-dichloropentane

A) only I
B) only II
C) I and III
D) I and II

Question 9

How many stereoisomers are there of D-fructose (including D-fructose), shown below?

A) four
B) six
C) eight
D) twelve

Question 10

Which compound below has no stereoisomers?

A) 1,2-dichlorobutane
B) 1,3-dichlorobutane
C) 2,3-dichlorobutane
D) 1,4-dichlorobutane

Question 11

Which one of the following is a diastereomer of (2R,3R)-2,3-dibromopentane?

A) (2S,3S)-2,3-dibromopentane
B) (2S,3R)-2,3-dibromopentane
C) R-1,2-dibromopentane
D) (2R,4R)-2,4-dibromopentane

Question 12

The tartaric acid found in fruits, when isolated, exhibits $[\alpha]=+12^{\circ}$ . Which configuration is NOT possible for this naturally-occurring material?

A) R, R
B) R, S
C) S, S
D) there is no way to tell