The structures of D – ( + ) – xylose , which oxidized to optically inactive aldaric acid and D – ( − ) – lyxose , which oxidized to optically active product, are to be determined. Concept introduction: 舧 A carbohydrate is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen-oxygen atom ratio of 2:1 舧 HNO 3 is an oxidizing agent. 舧 Carbohydrates are oxidized by HNO 3 to give aldaric acid as a product. 舧 Aldaric acids are carbohydrates having two carboxylic acids. They are formed due to oxidation reaction of aldoses with dilute HNO 3 and their general reaction can be represented as: 舧 The molecules that are nonsuperimposable or not identical with their mirror images are known as chiral molecules. 舧 A pair of two mirror images that are nonidentical is known as enantiomers, which are optically active. 舧 The stereoisomers that are nonsuperimposable on each other and not mirror images of each other are known as diastereomers. 舧 The achiral compounds in which plane of symmetry is present internally and consists of chiral centres are known as meso compounds, but they are optically inactive. 舧 Compounds that have a plane of symmetry tend to exist in meso forms. A meso form arises when the two stereoisomers produce superimposable images, and hence, compounds having meso forms are optically inactive. 舧 The Kiliani-Fischer reaction is used for increasing the number of carbon atoms of respective aldoses, thereby, lengthening the carbon chain of the compound. It is used to produce epimers of higher aldoses from a lower aldose, i.e., an aldose with a lesser number of carbon atoms produces a mixture having two epimeric aldoses with a higher number of carbon atoms. 舧 Oxidation of aldoses by nitric acid produces optically inactive aldaric acids. This is due to the formation of meso compounds. Compounds that do not form meso structures are optically active.

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Answer 1

Question

Definition Definition Class of organic compounds that contain a carboxyl group ( - COOH ) and has a general formula R - COOH or R - CO 2 H , where R refers to the alkyl, alkenyl, aryl, or other groups. They can undergo different chemical reactions, such as acid-base reactions, esterification, and oxidation. These are essential components of living organisms, playing important roles in metabolic processes, signaling, and as pharmaceuticals.

Chapter 22, Problem 15PP

Interpretation Introduction

Interpretation:

The structures of D–(+)–xylose, which oxidized to optically inactive aldaric acid and D–(−)–lyxose, which oxidized to optically active product, are to be determined.

Concept introduction:

舧 A carbohydrate is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen-oxygen atom ratio of 2:1

舧 HNO3 is an oxidizing agent.

舧 Carbohydrates are oxidized by HNO3 to give aldaric acid as a product.

舧 Aldaric acids are carbohydrates having two carboxylic acids. They are formed due to oxidation reaction of aldoses with dilute HNO3 and their general reaction can be represented as:

舧 The molecules that are nonsuperimposable or not identical with their mirror images are known as chiral molecules.

舧 A pair of two mirror images that are nonidentical is known as enantiomers, which are optically active.

舧 The stereoisomers that are nonsuperimposable on each other and not mirror images of each other are known as diastereomers.

舧 The achiral compounds in which plane of symmetry is present internally and consists of chiral centres are known as meso compounds, but they are optically inactive.

舧 Compounds that have a plane of symmetry tend to exist in meso forms. A meso form arises when the two stereoisomers produce superimposable images, and hence, compounds having meso forms are optically inactive.

舧 The Kiliani-Fischer reaction is used for increasing the number of carbon atoms of respective aldoses, thereby, lengthening the carbon chain of the compound. It is used to produce epimers of higher aldoses from a lower aldose, i.e., an aldose with a lesser number of carbon atoms produces a mixture having two epimeric aldoses with a higher number of carbon atoms.

舧 Oxidation of aldoses by nitric acid produces optically inactive aldaric acids. This is due to the formation of meso compounds. Compounds that do not form meso structures are optically active.

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Compound A is a D-aldopentose that can be oxidized to an optically inactive aldaric acid B. On Kiliani-Fischer chain extension, A is converted into C and D; C can be oxidized to an optically active aldaric acid E, but D is oxidized to an optically inactive aldaric acid F. What is the structure of compound F? • Use the wedge/hash bond tools to indicate stereochemistry where it exists. You do not have to explicitly draw H atoms. If a group is achiral, do not use wedged or hashed bonds on it. • Show stereochemistry in a meso compound. • Do not include lone pairs in your answer. They will not be considered in the grading.

Draw the structure of: (a) a polysaccharide formed by joining D-mannose units in 1→4-β- glycosidic linkages; (b) a polysaccharide formed by joining D-glucose units in 1→6-α- glycosidic linkages. The polysaccharide in (b) is dextran, a component of dental plaque.

Carbohydrates a. Compound Z is an aldopentose. If Z is oxidized with nitric acid the product is optically active. If Z undergoes one Ruff degradation and the product of that degradation is reduced to the alditol using H₂/Ni the resulting product is optically inactive. If compound Z undergoes two Ruff degradations, D-glyceraldehyde (shown below) is obtained. Draw the usual Fischer projection of Z (aldehyde at the top). (Hint: work backwards from D- glyceraldehyde.) H HIC OH CH₂OH D-Glyceraldehyde

Answer 2

Question

Definition Definition Class of organic compounds that contain a carboxyl group ( - COOH ) and has a general formula R - COOH or R - CO 2 H , where R refers to the alkyl, alkenyl, aryl, or other groups. They can undergo different chemical reactions, such as acid-base reactions, esterification, and oxidation. These are essential components of living organisms, playing important roles in metabolic processes, signaling, and as pharmaceuticals.

Chapter 22, Problem 15PP

Interpretation Introduction

Interpretation:

The structures of D–(+)–xylose, which oxidized to optically inactive aldaric acid and D–(−)–lyxose, which oxidized to optically active product, are to be determined.

Concept introduction:

舧 A carbohydrate is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen-oxygen atom ratio of 2:1

舧 HNO3 is an oxidizing agent.

舧 Carbohydrates are oxidized by HNO3 to give aldaric acid as a product.

舧 Aldaric acids are carbohydrates having two carboxylic acids. They are formed due to oxidation reaction of aldoses with dilute HNO3 and their general reaction can be represented as:

舧 The molecules that are nonsuperimposable or not identical with their mirror images are known as chiral molecules.

舧 A pair of two mirror images that are nonidentical is known as enantiomers, which are optically active.

舧 The stereoisomers that are nonsuperimposable on each other and not mirror images of each other are known as diastereomers.

舧 The achiral compounds in which plane of symmetry is present internally and consists of chiral centres are known as meso compounds, but they are optically inactive.

舧 Compounds that have a plane of symmetry tend to exist in meso forms. A meso form arises when the two stereoisomers produce superimposable images, and hence, compounds having meso forms are optically inactive.

舧 The Kiliani-Fischer reaction is used for increasing the number of carbon atoms of respective aldoses, thereby, lengthening the carbon chain of the compound. It is used to produce epimers of higher aldoses from a lower aldose, i.e., an aldose with a lesser number of carbon atoms produces a mixture having two epimeric aldoses with a higher number of carbon atoms.

舧 Oxidation of aldoses by nitric acid produces optically inactive aldaric acids. This is due to the formation of meso compounds. Compounds that do not form meso structures are optically active.

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Answer 3

Question

Definition Definition Class of organic compounds that contain a carboxyl group ( - COOH ) and has a general formula R - COOH or R - CO 2 H , where R refers to the alkyl, alkenyl, aryl, or other groups. They can undergo different chemical reactions, such as acid-base reactions, esterification, and oxidation. These are essential components of living organisms, playing important roles in metabolic processes, signaling, and as pharmaceuticals.

Chapter 22, Problem 15PP

Interpretation Introduction

Interpretation:

The structures of D–(+)–xylose, which oxidized to optically inactive aldaric acid and D–(−)–lyxose, which oxidized to optically active product, are to be determined.

Concept introduction:

舧 A carbohydrate is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen-oxygen atom ratio of 2:1

舧 HNO3 is an oxidizing agent.

舧 Carbohydrates are oxidized by HNO3 to give aldaric acid as a product.

舧 Aldaric acids are carbohydrates having two carboxylic acids. They are formed due to oxidation reaction of aldoses with dilute HNO3 and their general reaction can be represented as:

舧 The molecules that are nonsuperimposable or not identical with their mirror images are known as chiral molecules.

舧 A pair of two mirror images that are nonidentical is known as enantiomers, which are optically active.

舧 The stereoisomers that are nonsuperimposable on each other and not mirror images of each other are known as diastereomers.

舧 The achiral compounds in which plane of symmetry is present internally and consists of chiral centres are known as meso compounds, but they are optically inactive.

舧 Compounds that have a plane of symmetry tend to exist in meso forms. A meso form arises when the two stereoisomers produce superimposable images, and hence, compounds having meso forms are optically inactive.

舧 The Kiliani-Fischer reaction is used for increasing the number of carbon atoms of respective aldoses, thereby, lengthening the carbon chain of the compound. It is used to produce epimers of higher aldoses from a lower aldose, i.e., an aldose with a lesser number of carbon atoms produces a mixture having two epimeric aldoses with a higher number of carbon atoms.

舧 Oxidation of aldoses by nitric acid produces optically inactive aldaric acids. This is due to the formation of meso compounds. Compounds that do not form meso structures are optically active.

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Answer 4

Question

Definition Definition Class of organic compounds that contain a carboxyl group ( - COOH ) and has a general formula R - COOH or R - CO 2 H , where R refers to the alkyl, alkenyl, aryl, or other groups. They can undergo different chemical reactions, such as acid-base reactions, esterification, and oxidation. These are essential components of living organisms, playing important roles in metabolic processes, signaling, and as pharmaceuticals.

Chapter 22, Problem 15PP

Interpretation Introduction