Question 1

Which of the following best describes the structure shown in the first image (a five-membered ring with one oxygen atom)?

Accepted Answer

It is a furanose ring, commonly found in the cyclic form of fructose.

Question 2

What is the main difference between a Haworth projection and a chair conformation for carbohydrates?

Accepted Answer

A Haworth projection is a planar representation, while a chair conformation shows the three-dimensional arrangement of atoms.

Question 3

Which reagent selectively oxidizes the aldehyde group of a monosaccharide to a carboxylic acid without affecting primary alcohols?

Accepted Answer

$$\mathrm{Br_2$,\ H_2O}$$

Question 4

What is the product of the following reaction sequence: 1. $$\mathrm{$$NaBH_4$$,\ H_2O} 2$$. $$\mathrm{Br_2$,\ H_2O} on a $$glucose molecule?

Accepted Answer

A sugar acid with the aldehyde group reduced to an alcohol, then the new primary alcohol oxidized to a carboxylic acid (aldonic acid).

Question 5

Which of the following statements about glycoside formation is correct?

Accepted Answer

Glycoside formation involves the reaction of a hemiacetal with an alcohol to form an acetal.

Question 6

Which of the following best describes an epimer in carbohydrate chemistry?

Accepted Answer

A diastereomer that differs by exactly one chiral center.

Question 7

What is the consequence of epimerization at the C-2 position of glucose?

Accepted Answer

It converts glucose into mannose.

Question 8

Which of the following is true regarding the equilibrium between hemiacetal and open-chain forms of glucose?

Accepted Answer

The hemiacetal form is in equilibrium with the open-chain aldehyde form, allowing for mutarotation.

Question 9

Which reaction sequence is used to lengthen a carbohydrate chain by one carbon atom?

Accepted Answer

Kiliani-Fischer synthesis

Question 10

Which of the following statements about acetals and hemiacetals in carbohydrate chemistry is correct?

Accepted Answer

Acetals are stable and do not equilibrate with the open-chain form, while hemiacetals do.

Question 11

Which of the following best describes the product when glucose is treated with $$\mathrm{$$HNO_3$$,\ H_2O,\ \Delta}$$?

Accepted Answer

Both the aldehyde and the primary alcohol are oxidized to carboxylic acids.

Question 12

Which of the following is NOT a property of glycosides?

Accepted Answer

They are in equilibrium with their open-chain forms.

Question 13

Which of the following is the correct Haworth projection for D-glucose?

Accepted Answer

Option B in the fifth image.

Question 14

What is the effect of $$\mathrm{$$NaBH_4$$} on a $$carbohydrate in its acetal (glycoside) form?

Accepted Answer

No reaction occurs because acetals are not in equilibrium with the open-chain form.

Question 15

Which of the following best describes the mechanism of epimerization?

Accepted Answer

Interconversion between two sugars that differ at a single chiral center via enolization.

Carbohydrate Structure and Reactions: Projections, Epimerization, Redox, and Chain Modification

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