Question 1

Which of the following statements about Fischer projections is CORRECT?

Accepted Answer

A 180-degree rotation of a Fischer projection is allowed and does not change the molecule's configuration.

Question 2

Given the Fischer projection below, what is the D/L configuration of the sugar?

$$\begin{array}{c}
\mathrm{CHO} \
\mathrm{H}~|~\mathrm{OH} \
\mathrm{HO}~|~\mathrm{H} \
\mathrm{H}~|~\mathrm{OH} \
\mathrm{CH_2OH}
\end{array}$$

Accepted Answer

D

Question 3

Which operation on a Fischer projection will produce an enantiomer of the original molecule?

Accepted Answer

Swapping any two groups at a single chiral center

Question 4

Which of the following best describes the difference between anomers?

Accepted Answer

They differ at the configuration of the anomeric carbon after cyclization.

Question 5

What is the product when D-glucose cyclizes to form a pyranose ring?

Accepted Answer

A six-membered ring with an oxygen atom

Question 6

Which of the following is TRUE regarding the interconversion of alpha and beta anomers of glucose?

Accepted Answer

It is called mutarotation and occurs in aqueous solution.

Question 7

Given the following Fischer projection, which Haworth projection correctly represents the beta-anomer of D-glucose?

Accepted Answer

The anomeric OH is cis to the CH$$_2OH $$group.

Question 8

Which of the following is a correct statement about the chair conformation of cyclohexane derivatives?

Accepted Answer

Equatorial substituents are generally more stable due to less steric hindrance.

Question 9

Which of the following best describes the process of hemiacetal formation in carbohydrates?

Accepted Answer

An aldehyde reacts with an alcohol to form a hemiacetal.

Question 10

How many possible stereoisomers exist for a carbohydrate with 4 chiral centers?

Accepted Answer

$$2^4 = 16$

Question 11

Which of the following is NOT a valid operation on a Fischer projection?

Accepted Answer

Swapping two groups at a chiral center

Question 12

Which of the following best describes the relationship between D-glucose and D-fructose?

Accepted Answer

They are constitutional isomers.

Question 13

Which of the following is TRUE about the conversion between open and closed forms of carbohydrates?

Accepted Answer

The open and closed forms are in equilibrium in aqueous solution.

Question 14

Which of the following is a correct statement about the Haworth projection of a pyranose ring?

Accepted Answer

The anomeric carbon is the carbonyl carbon in the open-chain form.

Question 15

Which of the following best describes the difference between a pyranose and a furanose?

Accepted Answer

A pyranose has a six-membered ring, while a furanose has a five-membered ring.

Question 16

Which of the following is TRUE regarding the stereochemistry of carbohydrates?

Accepted Answer

Carbohydrates can have multiple chiral centers, leading to many possible stereoisomers.

Question 17

Which of the following is a valid method for drawing the enantiomer of a given Fischer projection?

Accepted Answer

Swap any two groups at every chiral center.

Question 18

Which of the following best describes the relationship between the chair and Haworth projections of glucose?

Accepted Answer

The chair projection is a more accurate 3D representation of the Haworth projection.

Question 19

Which of the following is TRUE about the mechanism of carbohydrate cyclization?

Accepted Answer

The nucleophilic attack of an alcohol group on the carbonyl carbon forms a hemiacetal.

Representations and Stereochemistry of Carbohydrates

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