Concept explainers
Interpretation:
The structures of
Concept introduction:
舧 A carbohydrate is a
舧
舧 Carbohydrates are oxidized by
舧 Aldaric acids are carbohydrates having two
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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Organic Chemistry
- 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-Glyceraldehydearrow_forwardRegarding 4-O- (α-D-psychofuranosyl) -β-D-allopyranose. Please indicate the RIGHT alternative: (a) The disaccharide reacts with CH3OH in an acid medium to form a glycoside that cannot be oxidized with HNO3. (b) It is a reducing disaccharide only in basic medium. (c) In the structure there is only one glycosidic bond that is of the type β 1-O-4 ' (d) The hydrolysis products of this disaccharide do not show mutarrotation. (e) The disaccharide structure contains two six-membered rings.arrow_forwardWhich D-aldopentoses are reduced to optically inactive alditols using NaBH4, CH3OH?arrow_forward
- Draw the structure of: (a) a polysaccharide formed by joining D-mannose units in 1->4-ß-glycosidic linkages; (b) a polysaccharide formed by joining D-glucose units in 1->6-a-glycosidic linkages. The polysaccharide in (b) is dextran, a component of dental plaque.arrow_forwardA D-aldopentose A is reduced to an optically active alditol. Upon Kiliani–Fischer synthesis, A is converted to two D-aldohexoses, B and C. B is oxidized to an optically inactive aldaric acid. C is oxidized to an optically active aldaric acid. What are the structures of A–C?arrow_forwardMonosaccharide A is a diastereomer of d-lyxose. Treatment of A with nitric acid forms an optically inactive aldaric acid. A undergoes a Kiliani-Fischer synthesis to form B and C. B is oxidized by nitric acid to an optically active aldaric acid, and C is oxidized to an optically inactive aldaric acid. Wohl degradation of A forms D, which is oxidized by nitric acid to an optically inactive aldaric acid. Wohl degradation of D forms a d-aldotriose. Identify A, B, C, and D.arrow_forward
- A D-aldopentose A is oxidized to an optically inactive aldaric acid with HNO3. A is formed by the Kiliani–Fischer synthesis of a D-aldotetrose B, which is also oxidized to an optically inactive aldaric acid with HNO3. What are the structures of A and B?arrow_forwardWhich D-aldopentoses are reduced to optically inactive alditols using NaBH,, CH;OH?arrow_forwardCompound 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.)arrow_forward
- Aldohexoses A and B are formed from aldopentose C via a Kiliani–Fischer synthesis. Nitric acid oxidizes A to an optically active aldaric acid, B to an optically inactive aldaric acid, and C to an optically active aldaric acid. Wohl degradation of C forms D, which is oxidized by nitric acid to an optically active aldaric acid. Wohl degradation of D forms (+)-glyceraldehyde. Identify A, B, C, and D.arrow_forwardAn optically active D-aldopentose (A) produced an optically inactive alditol (B) upon treatment with H2/Pt. When the aldopentose (A) was subjected to a Ruff degradation, D-aldotetrose (C) was generated. The aldotetrose (C) gave an optically active aldaric acid (D) upon oxidation with HNO3. D-aldopentose (A) can be prepared from D-threose by a Killani Fischer synthesis. Propose structure of A through D.arrow_forwardThere are three (3) vials labeled A, B, and C known to contain the following monosaccharides. All three samples reduce Tollens and Fehling. By oxidation with dilute HNO3 an optically active aldaric acid is obtained for sample A and the remaining two give products without optical activity. When the three samples were subjected to an alkaline medium, it was observed that, after a certain time, samples A and C reached the same value of the specific rotation [α]. Select the RIGHT alternative: (a) Sample A is Galactose. (b) Sample B is Alosa. (c) Samples A and C are not related to each other by an epimerization process. (d) Sample C is Talose. (e) Samples B and C are epimers.arrow_forward
- Chemistry for Today: General, Organic, and Bioche...ChemistryISBN:9781305960060Author:Spencer L. Seager, Michael R. Slabaugh, Maren S. HansenPublisher:Cengage Learning