Concept explainers
Interpretation:
The series of
Concept introduction:
舧 Formation of isomers is called isomerization. Monosaccharides undergo a series of keto-enol tautomerizations and enolizations and to produce different isomeric forms. In order to preserve the stereochemical nature of the compounds, the formation of such isomeric forms needs to be prevented.
舧 Stereochemistry: A carbon atom is attached to four distinct groups is said to be a stereogenic or chirality center of that molecule. A stereocenter is that point in a molecule where any two groups exchange their positions to form stereoisomers.
舧 The pair of diastereomers that shows different configuration at the chirality center are called epimers. The aldohexoses,
舧 A carbohydrate is a
舧
舧 Carbohydrates are oxidized by
舧 Aldaric acids are carbohydrates having two
舧 Monosaccharides containing six carbon atoms and an
舧 Alditols are compounds produced from aldoses or ketoses on reduction with certain reagents such as sodium borohydride (
舧 Compounds formed by the reaction of reducing sugars with excess of phenyl hydrazine are called osazones. Osazones are products of oxidation and are produced by all reducing sugars.
舧
舧 Fischer projection is a way of representing the structural formulae of compounds through cross formulation of their open chain structures.
舧 Bromine water is an effective reagent that selectively oxidizes the
舧 While dissolved in aqueous bases such as pyridine, monosaccharides undergo complex isomerization as they form different enols and keto-enols. Aldonic acids form epimers (usually at the
Want to see the full answer?
Check out a sample textbook solutionChapter 22 Solutions
Organic Chemistry
- Emil Fischer synthesized l-gulose, an unusual aldohexose that reduces to give d-glucitol.Suggest a structure for this l sugar, and show how l-gulose gives the same alditol asd-glucose. (Hint: d-Glucitol has ¬CH2OH groups at both ends. Either of these primaryalcohol groups might have come from reduction of an aldehyde.)arrow_forwardA D-aldohexose A is formed from an aldopentose B by the Kiliani-Fischer synthesis. Reduction of A with NABH4 forms an optically inactive alditol. Oxidation of B forms an optically active aldaric acid. What are the structures of A and B?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_forward
- (a) Which of the d-aldopentoses will give optically active aldaric acids on oxidation with HNO3 ?(b) Which of the d-aldotetroses will give optically active aldaric acids on oxidation with HNO3 ?(c) Sugar X is known to be a d-aldohexose. On oxidation with HNO3, X gives an optically inactive aldaric acid. WhenX is degraded to an aldopentose, oxidation of the aldopentose gives an optically active aldaric acid. Determine thestructure of X.(d) Even though sugar X gives an optically inactive aldaric acid, the pentose formed by degradation gives an opticallyactive aldaric acid. Does this finding contradict the principle that optically inactive reagents cannot form opticallyactive products?(e) Show what product results if the aldopentose formed from degradation of X is further degraded to an aldotetrose.Does HNO3 oxidize this aldotetrose to an optically active aldaric acid?arrow_forwardIf lactose is first hydrolyzed (by addition of sulfuric acid) into its constituent monosaccharide, and then subjected to complete methylation, what methylated products do you expect?arrow_forwardMonosaccharide A is a D-aldotetrose. Treatment of A with nitric acid gives an optically inactive aldaric acid (B). Killiani-Fischer chain extension of A gives two products (C & D). C on treatment with NABH4, gives an alditol (E) that is optically active. D gives an alditol (F) that is NOT optically active. Give Fischer projections for A, B, CD, E, and E.arrow_forward
- What is the product of the starting material D-glyceraldehyde which will (1) produce aldaric acid upon reacting with HNO3 + H2O, NaOCH2, NH2OH, and (CH3CO)2O + NaOCOCH3 (2) produce tartaric acid upon reacting with HNO3 + H2O, NaOCH3, NH2OH, and (CH3CO)2O + NaOCOCH3arrow_forwardAn important technique for establishing relative configurations among isomeric aldoses and ketoses is to convert both terminal carbon atoms to the same functional group. This can be done either by selective oxidation or reduction. As a specific example, nitric acid oxidation of d-erythrose gives meso-tartaric acid . Similar oxidation of d-threose gives (2S,3S)-tartaric acid. Given this information and the fact that d-erythrose and d-threose are diastereomers, draw Fischer projections for d-erythrose and d-threose. Check your answers against Table 25.1.arrow_forwardPredict the products formed when the following sugars react with excess acetic anhydrideand pyridine.(a) a-d-glucopyranose (b) b-d-ribofuranosearrow_forward
- The reagent periodate (IO,") oxidatively cleaves the carbon-carbon bonds between two adjacent carbons carrying hydroxyl groups. Explain how pe- riodate oxidation might be used to distinguish between methyl glycosides of glucose in the pyranose and furanose forms.arrow_forwardTrehalose, C12H22O11, is a nonreducing sugar that is only 45% as sweet as sugar. When hydrolyzed by aqueous acid or the enzyme maltase, it formsonly d-glucose. When it is treated with excess methyl iodide in the presence of Ag2O and then hydrolyzed with water under acidic conditions, only2,3,4,6-tetra-O-methyl-d-glucose is formed. Draw the structure of trehalose.arrow_forwardIllustrate the treatment of methyl α-D-glucopyranoside with aqueous acid forms a mixture of α- and β-D-glucose and methanol ?arrow_forward
- ChemistryChemistryISBN:9781305957404Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCostePublisher:Cengage LearningChemistryChemistryISBN:9781259911156Author:Raymond Chang Dr., Jason Overby ProfessorPublisher:McGraw-Hill EducationPrinciples of Instrumental AnalysisChemistryISBN:9781305577213Author:Douglas A. Skoog, F. James Holler, Stanley R. CrouchPublisher:Cengage Learning
- Organic ChemistryChemistryISBN:9780078021558Author:Janice Gorzynski Smith Dr.Publisher:McGraw-Hill EducationChemistry: Principles and ReactionsChemistryISBN:9781305079373Author:William L. Masterton, Cecile N. HurleyPublisher:Cengage LearningElementary Principles of Chemical Processes, Bind...ChemistryISBN:9781118431221Author:Richard M. Felder, Ronald W. Rousseau, Lisa G. BullardPublisher:WILEY