Deck 28: Carbohydrates

Question 1

Which of the following is a reducing sugar?

A) A
B) B
C) C
D) D

Answer 1

D

Question 2

Which of the following compounds is an aldose?

A) A
B) B
C) C
D) D

Answer 2

B

Question 3

Which of the following reagents would convert glucose into ethyl glucopyranoside?

A) EtBr, aq. HCl
B) EtOH, aq. HCl
C) EtOH, NaOH
D) Ag₂O in NH₄OH

Answer 3

EtOH, aq. HCl

Question 4

Amylose is a polysaccharide with ________________________ linkages.

A) " $\beta$ -1,4'-glycosidic"
B) " $\alpha$ -1,4'-glycosidic"
C) " $\beta$ -1,6'-glycosidic"
D) " $\alpha$ -1,6'-glycosidic"

Question 5

How many carbons does a pentose sugar have?

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

Question 6

Which of the following compounds is a $\beta$ anomer?

A) A
B) B
C) C
D) D

Question 7

Which is the correct Haworth projection for the $\beta$ anomer of D-glucose?

A) A
B) B
C) C
D) D

Question 8

What is the correct chair form for the $\beta$ anomer of D-glucose?

A) A
B) B
C) C
D) D

Question 9

Does a monosaccharide prefer to exist in the open-chain or closed-ring form?

A) open
B) closed
C) Both forms exist in equal ratios.

Question 10

Which is the correct Haworth projection for the $\alpha$ anomer of allose?

A) A
B) B
C) C
D) D

Question 11

Which of the following compounds is not a valid representation for D-glucose?

A) A
B) B
C) C
D) D
E) E

Question 12

What are the products of the following reaction?

A) A
B) B
C) C
D) D

Question 13

Which is the correct Fischer projection for the open-chain form of the carbohydrate shown below?

A) A
B) B
C) C
D) D

Question 14

What is the process called for the interconversion of one anomer to the other?

A) racemization
B) mutarotation
C) epimerization
D) enolization

Question 15

Which of the following pairs of carbohydrates will afford the same product from a Wohl degradation?

A) xylose/glucose
B) ribose/arabinose
C) fructose/mannose
D) lyxose/threose

Question 16

Is the following carbohydrate D or L? Provide an explanation for your answer.

A) It is D because the OH group on C2 is on the right.
B) It is L because the OH group on C4 is on the left.
C) It is L because the OH group on C3 is on the left.
D) It is D because the sugar is not symmetric.

Question 17

How many possible stereoisomers are there of the following heptose?

A) 16
B) 21
C) 32
D) 64

Question 18

What is the correct chair form for the $\alpha$ anomer of D-mannose?

A) A
B) B
C) C
D) D

Question 19

Which of the following reagents will selectively oxidize an aldose to an aldonic acid?

A) PCC
B) Ag₂O in NH₄OH
C) FeCl₃
D) HNO₃

Question 20

Cellulose is a polysaccharide with ________________________ linkages.

A) " $\beta$ -1,4'-glycosidic"
B) " $\alpha$ -1,4'-glycosidic"
C) " $\beta$ -1,6'-glycosidic"
D) " $\alpha$ -1,6'-glycosidic"

Question 21

From the sugars shown below, which one is a non-reducing sugar?

A) A
B) B
C) C
D) D

Question 22

Upon hydrolysis of cellulose, what sugar is formed?

A) sucrose
B) maltose
C) lactose
D) glucose

Question 23

Upon hydrolysis of amylose, what sugar is formed?

A) sucrose
B) maltose
C) lactose
D) glucose

Question 24

The branching units in amylopectin, a polysaccharide, which enable this molecule to be water soluble are connected with __________________________ linkages.

A) " $\beta$ -1,4'-glycosidic"
B) " $\alpha$ -1,4'-glycosidic"
C) " $\alpha$ -1,6'-glycosidic"
D) " $\beta$ -1,6'-glycosidic"

Question 25

From the disaccharides listed below, which one will not undergo mutarotation?

A) sucrose
B) maltose
C) lactose
D) xylobiose

Question 26

After a series of Kiliani-Fischer syntheses on D-glyceraldehyde, an unknown sugar was isolated from the reaction mixture. The following experimental data was obtained. What is the structure of this unknown sugar? Data:
- Molecular formula: C₆H₁₂O₆
- Reacts with phenylhydrazine to give an osazone, mp 178°C.
- Reacts with HNO₃ to give an optically active aldaric acid.
- Wohl degradation followed by HNO₃ oxidation gives an optically inactive
Aldaric acid.
- Two Wohl degradations followed by HNO₃ oxidation give a meso-tartaric acid.

A) A
B) B
C) C
D) D

Question 27

From the sugars shown below, which one will not give a positive test with Tollens reagent?

A) A
B) B
C) C
D) D

Question 28

Which of the following sugars can be classified as a ketopentose?

A) A
B) B
C) C
D) D

Question 29

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

A) enantiomers
B) epimers
C) anomers
D) constitutional isomers

Question 30

What is the best description of the product formed in the following reaction sequence?

A) The product is an optically active aldonic acid.
B) The product is an optically inactive aldonic acid.
C) The product is an optically active aldaric acid.
D) The product is an optically inactive aldaric acid.

Question 31

The following reaction is an example of a base-catalyzed epimerization reaction in which a ketose is converted to a pair of aldoses. What are the products from this reaction?

A) D-glucose and D-mannose
B) D-galactose and D-talose
C) D-talose and D-idose
D) D-glucose and D-idose

Question 32

Oxidation of a D-hexose with nitric acid forms an optically active aldaric acid. A Wohl degradation of the same D-hexose followed by oxidation with nitric acid forms an optically active aldaric acid. What are the three possible D-hexoses that fit this data?

A) D-allose, D-altrose and D-glucose
B) D-glucose, D- mannose and D-talose
C) D-glucose, D-idose and D-altrose
D) D-galactose, D-talose and D-mannose

Question 33

Which sugar is represented by the line angle structure below?

A) D-fructose
B) D-sorbose
C) L-psicose
D) L-tagatose

Question 34

What is the composition of sucrose?

A) two glucose units with a $\alpha$ -1,4'-glycoside bond
B) one glucose and one fructose unit with a $\alpha$ -glycosidic bond to the 2'carbon of a fructofuranose ring
C) one galactose and one glucose unit with a $\beta$ -1,4'-glycoside bond
D) repeating unit of glucose units joined in a $\beta$ -1,4'-glycosidic linkage

Question 35

What is the composition of maltose?

A) two glucose units with a $\alpha$ -1,4'-glycoside bond
B) one glucose and one fructose unit with a $\alpha$ -glycosidic bond to the 2'carbon of a fructofuranose ring
C) one galactose and one glucose unit with a $\beta$ -1,4'-glycoside bond
D) repeating unit of glucose units joined in a $\beta$ -1,4'-glycosidic linkage

Question 36

Upon hydrolysis of amylopectin, what sugar is formed?

A) sucrose
B) maltose
C) lactose
D) glucose

Question 37

Which of the following sugars can be classified as a ketohexose?

A) A
B) B
C) C
D) D

Question 38

What is the composition of lactose?

A) two glucose units with a $\alpha$ -1,4'-glycoside bond
B) one glucose and one fructose unit with a $\alpha$ -glycosidic bond to the 2'carbon of a fructofuranose ring
C) one galactose and one glucose unit with a $\beta$ -1,4'-glycoside bond
D) repeating unit of glucose units joined in a $\beta$ -1,4'-glycosidic linkage

Question 39

Which of the following sugars can be classified as a ketotetrose?

A) A
B) B
C) C
D) D

Question 40

Which of the following sugars can be classified as an aldohexose?

A) A
B) B
C) C
D) D

Question 41

What is the classification of pyranose forms of monosaccharides?

A) 5-membered cyclic hemiacetals
B) 6-membered cyclic acetals
C) 5-membered cyclic acetals
D) 6-membered cyclic hemiacetals