Deck 20: The Organic Chemistry of Carbohydrates

Question 1

Which of the following best describes the sugar D-galactose?

A)D-aldohexose
B)D-ketohexose
C)L-aldohexose
D)L-ketohexose
E)D-aldopentose

Answer 1

D-aldohexose

Question 2

At which carbon are the following sugars epimers of each other?

A)C-1
B)C-2
C)C-3
D)C-4
E)C-5

Answer 2

C-3

Question 3

The open-chain form of D-idose is shown below.Draw the open-chain form of the C-3 epimer of D-idose.

Answer 3

Question 4

Which of the following compounds is a D-sugar?

A)
B)
C)
D)
E)

Question 5

Draw L-erythrose.

Question 6

All chiral D-sugars rotate plane-polarized light

A)clockwise.
B)counterclockwise.
C)+20.0°.
D)in a direction that cannot be predicted but must be determined experimentally.
E)since they are optically inactive.

Question 7

Which of the following corresponds to the definition of an aldopentose? I.It is a monosaccharide.
II)It contains a CHO group
III)It is a disaccharide.
IV)It is an oligosaccharide.

A)I and II
B)II and III
C)I and IV
D)I and III
E)I,II,and III

Question 8

Draw the Fischer projection for the open-chain form of D-glucose.

Question 9

At which carbon are the following sugars epimers of each other?

A)C-1
B)C-2
C)C-3
D)C-4
E)C-5

Question 10

What is the relationship between the following compounds?

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

Question 11

How many chirality centers are there in an aldohexose?

A)2
B)3
C)4
D)5
E)6

Question 12

A carbohydrate composed of three to ten sugar molecules is called a(n)

A)single carbohydrate.
B)disaccharide.
C)oligosaccharide.
D)polysaccharide.
E)monosaccharide.

Question 13

How many chirality centers are there in a 2-ketohexose?

A)2
B)3
C)4
D)5
E)6

Question 14

At which carbon are the following sugars epimers of each other?

A)C-1
B)C-2
C)C-3
D)C-4
E)C-5

Question 15

Draw the Fischer projection for the open-chain form of D-erythrose.

Question 16

Assign the proper configurational descriptor to each asymmetric center in D-glucose below.

Question 17

How many stereoisomers are possible for a 2-ketohexose?

A)2
B)4
C)8
D)16
E)32

Question 18

Is the following structure of glucose a D or L configuration? Explain.

Question 19

Which of the following statements best describes the difference between amylose and amylopectin?

A)Amylose is a branched polysaccharide while amylopectin is a chain polysaccharide.
B)Amylose is a straight-chain polysaccharide while amylopectin is a branched polysaccharide.
C)Amylose contains α-1,6-glycosidic linkage which amylopectin does not contain.
D)Amylose is composed of thousands of D-glucose units while amylopectin is composed of thousands of D-galactose units.
E)Amylose is one of the largest molecules found in nature while amylopectin is one of the smallest molecules found in nature.

Question 20

Is L-glucose the enantiomer of D-glucose,the C-5 epimer of D-glucose,or both?

Question 21

Give the major product(s)for the reaction.You may choose more than one answer.

A)
B)
C)
D)
E)

Question 22

Provide the Fischer projection of the open-chain form of the aldonic acid which results when L-glucose is treated with bromine water.

Question 23

An optically active D-aldopentose produced an optically active alditol upon treatment with NaBH₄.When this aldopentose was subjected to a Ruff degradation,a D-aldotetrose was generated.This aldotetrose gave an optically active aldaric acid upon oxidation with HNO₃.Use these data to provide the structure of the starting D-aldopentose.

Question 24

Provide the major organic product(s)of the reaction below.

Question 25

Which of the D-aldopentoses yields an optically inactive aldonic acid upon oxidation with bromine water? Explain your answer.

Question 26

An optically active D-aldopentose produced an optically inactive aldaric acid upon treatment with HNO₃.When this aldopentose was subjected to a Ruff degradation,a D-aldotetrose was generated.This aldotetrose gave an optically inactive alditol upon reduction with NaBH₄.Use these data to provide the structure of the starting D-aldopentose.

Question 27

An optically active D-aldopentose A produced an optically active alditol B upon treatment with sodium borohydride.When this aldopentose was subjected to a Ruff degradation,a D-aldotetrose C was generated.This aldotetrose yielded an optically inactive aldaric acid D upon oxidation with nitric acid.Use these data to provide the structures of compounds A,B,C,and D.

Question 28

Provide the major organic product(s)of the reaction below.

Question 29

Name the following compound.

A)D-glucose
B)D-galactose
C)D-fructose
D)D-arabinose
E)D-talose

Question 30

Which of the following sugars yields the same alditol upon reduction with NaBH₄ as does D-glucose?

A)D-fructose
B)D-mannose
C)L-glucose
D)D-arabinose
E)none of the above

Question 31

Which of the following monosaccharides will form D-glucaric acid upon oxidation with nitric acid?

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

Question 32

Provide the structure of the product which results when D-ribose is treated with bromine water.

Question 33

Which of the following is/are the product(s)obtained from the reduction of D-fructose?

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

Question 34

Reduction of a 2-ketohexose with NaBH₄ yields

A)a single aldohexose.
B)a mixture of acetals.
C)a mixture of alditols.
D)a mixture of cyclic hemiacetals.
E)a single pyranose.

Question 35

An optically active D-aldopentose produced an optically inactive alditol upon treatment with NaBH₄.When this aldopentose was subjected to a Ruff degradation,a D-aldotetrose was generated.This aldotetrose gave an optically active aldaric acid upon oxidation with HNO₃.Use these data to provide the structure of the starting D-aldopentose.

Question 36

When D-sorbose (shown below)is treated with NaBH₄,which of the following is produced?

A)a single optically active alditol
B)a single optically inactive alditol
C)a racemic mixture of alditols
D)an optically inactive mixture of epimeric alditols
E)an optically active mixture of epimeric alditols

Question 37

Draw the Fischer projection for the open-chain form of D-fructose.

Question 38

When D-tagatose is added to a basic aqueous solution,an equilibrium mixture of three monosaccharides is obtained.Identify the monosaccharides.

Question 39

When D-threose is treated with NaBH₄

A)a 70:30 mixture of enantiomeric alditols results.
B)a 50:50 mixture of enantiomeric alditols results.
C)a meso alditol is produced.
D)the product mixture contains two diastereomeric alditols.
E)an optically active alditol is produced.

Question 40

Give the major product(s)for the reaction.

A)
B)
C)
D)
E)

Question 41

Give the product(s)for each step of the following reaction.

Question 42

Provide the open-chair structures of the two monosaccharides that result when D-threose undergoes the Kiliani-Fischer synthesis.

Question 43

What nucleophilic carbon species is used in the Kiliani-Fischer synthesis?

Question 44

Give the major product(s)for the following reaction.

A)no reaction
B)
C)
D)
E)

Question 45

Which of the following is the Haworth projection of a α-D-tagatofuranose?

A)I
B)II
C)III
D)IV
E)V

Question 46

Give the product(s)for each step of the following reaction.

Question 47

Two D-aldopentoses give the same D-aldotetrose upon Ruff degradation.The two aldopentoses are

A)enantiomers.
B)meso compounds.
C)C2 epimers.
D)C4 epimers.
E)D-glucose and D-galactose.

Question 48

Which of the following is the Haworth projection of β-D-galactopyranose?

A)I
B)II
C)III
D)IV
E)V

Question 49

Give the major product(s)for the following reaction.

A)no reaction
B)
C)
D)
E)

Question 50

Which of the following statements best describes the meaning of mutorotation?

A)a rapid exchange between the α and β forms of diasternomeric sugars
B)a rapid exchange between the D and L forms
C)a slow exchange between hydrogen and deuterated hydrogen
D)a slow change in optical rotation to reach an equilibrium value
E)a slow change in absolute configuration to reach an equilibrium value

Question 51

Which of the following sequences is known as a Kiliani-Fischer chain elongation?

A)1)Fe³⁺,H₂O₂ 2.Br₂,H₂O 3.Ca(OH)₂
B)1)CN^- 2.H₂,Pd/BaSO₄ 3.H₃O⁺
C)1)NaBH₄ 2.H₂O 3.Br₂,H₂O
D)1)acetic anhydride (excess),pyridine 2.CH₃I (excess),Ag₂O
E)1)CH₃OH,H⁺,Δ 2.AgNO₃,Δ

Question 52

Give the major product(s)for the following reaction.

A)no reaction
B)
C)
D)
E)

Question 53

In solution,glucose exists as

A)the open-chain form only.
B)the cyclic hemiacetal form only.
C)the cyclic acetal form only.
D)an equilibrium mixture of the open-chain form and cyclic acetal forms.
E)an equilibrium mixture of the open-chain form and cyclic hemiacetal forms.

Question 54

Which monosaccharides are formed in the Kiliani-Fischer synthesis starting with D-xylose?

A)D-glucose and D-mannose
B)D-glucose and D-idose
C)D-galactose and D-talose
D)D-allose and D-altrose
E)D-ribose and D-arabinose

Question 55

Give the major product(s)for the following reaction.

A)no reaction
B)
C)
D)
E)

Question 56

Which two monosaccharides can be degraded by the Ruff Degradation to D-arabinose?

A)D-allose and D-altrose
B)D-glucose and D-idose
C)D-galactose and D-talose
D)D-erythrose and D-threose
E)D-glucose and D-mannose

Question 57

Which of the following is the cyclic hemiacetal formed from 4-hydroxyheptanal?

A)I
B)II
C)III
D)IV
E)V

Question 58

Give the major product(s)for the following reaction.

A)no reaction
B)
C)
D)
E)

Question 59

When a monosaccharide reacts to give the pyranose form from its open-chain form,how many distinct pyranose forms are possible?

A)1
B)2
C)2ⁿ,where n is the number of carbons present
D)4n + 2,where n is the number of carbons present
E)4

Question 60

An aqueous solution of glucose behaves as an aldehyde because

A)it is hydrolyzed by water to the free aldehyde.
B)it is a ketone,but is in equilibrium with the aldehyde form.
C)glucose is actually a cyclic aldehyde.
D)its cyclic hemiacetal,the predominant form,is in equilibrium with the free aldehyde form.
E)it can be oxidized with periodic acid.

Question 61

Draw the Haworth structure of α-D-ribofuranose.

Question 62

Six-membered cyclic hemiacetals and five-membered cyclic hemiacetals are called,respectively

A)mannoses and xyloses.
B)maltoses and arabinoses.
C)pyranoses and fructoses.
D)glycoses and fructoses.
E)none of the above.

Question 63

The open-chain form of D-idose is shown below.Draw the Haworth projection of a-D-idopyranose.

Question 64

Given the structure of D-altrose below,provide the Haworth structure of β-D-altropyranose.

Question 65

Provide the Haworth projection of ethyl-β-D-mannopyranoside.

Question 66

Draw the Haworth structure of β-D-glucopyranose

Question 67

A pyranose with the hydroxyl group on the anomeric carbon pointing up in the Haworth structure is designated

A)a'.
B)b'.
C)α)
D)β)
E)f)

Question 68

Why is β-D-glucopyranose more stable in nature than α-D-glucopyranose?

Question 69

Which of the following is methyl-α-D-glucopyranoside?

A)I
B)II
C)III
D)IV
E)V

Question 70

Draw the more stable chair conformer of α-D-glucopyranose.

Question 71

Anomers of D-glucopyranose differ in their stereochemistry at

A)C1.
B)C2.
C)C3.
D)C4.
E)C5.

Question 72

Which of the following statements best describes the meaning of a glycoside?

A)It is the mirror image of a sugar.
B)It is the hemiacetal of a sugar.
C)It is the acetal of a sugar.
D)It is the enantiomer of a sugar.
E)It is the enol-keto form of a sugar.

Question 73

Which of the following statements regarding methyl-β-L-glucopyranoside is correct?

A)This glycoside is a reducing sugar.
B)This glycoside undergoes mutorotation in aqueous base.
C)This glycoside will undergo no reaction when treated with excess CH₃I/Ag₂O.
D)This glycoside will be hydrolyzed to the cyclic hemiacetal in dilute aqueous acid.
E)This glycoside will readily undergo Kiliani-Fischer chain elongation.

Question 74

Under what conditions is the methyl glycoside of galactose prepared?

Question 75

When pure α-D-glucopyranose is dissolved in water,the optical rotation of the resulting solution changes over a period of time.What is the name of this phenomenon and why does it occur?

Question 76

The open-chain form of D-idose is shown below.Draw the Haworth projection of b-D-idopyranose.

Question 77

Given the structure of D-arabinose below,provide the structure of the glycoside methyl α-D-arabinofuranoside.

Question 78

Which of the following compounds is a nonreducing sugar?

A)I
B)II
C)III
D)IV
E)V

Question 79

Give the name for the following structure.

Question 80

Given the structure of D-talose below,provide the Haworth structure of α-D-talopyranose.