Concept explainers
(a)
Interpretation: The aldoses formed when D-threose is subjected to the Kiliani–Fischer synthesis are to be predicted.
Concept introduction: Kiliani–Fischer synthesis is a method which is used for the elongation of the carbon chains in aldose. In this method, the aldose chain is elongated by the formation of new stereogenic centre at
(b)
Interpretation: The aldoses formed when D-ribose is subjected to the Kiliani–Fischer synthesis are to be predicted.
Concept introduction: Kiliani–Fischer synthesis is a method which is used for the elongation of the carbon chains in aldose. In this method, the aldose chain is elongated by the formation of new stereogenic centre at
(c)
Interpretation: The aldoses formed when D-galactose is subjected to the Kiliani–Fischer synthesis are to be predicted.
Concept introduction: Kiliani–Fischer synthesis is a method which is used for the elongation of the carbon chains in aldose. In this method, the aldose chain is elongated by the formation of new stereogenic centre at
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Organic Chemistry
- (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_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_forwardWhich D-aldopentoses are reduced to optically inactive alditols using NaBH4, CH3OH?arrow_forward
- 1. Draw Haworth projections of B-D-arabinofuranose and a-L-mannopyranose. 2. Consider the structure of the disaccharide drawn at right: НО `CH2 В ОН (a) Give the names and D/L designation for the two monosaccharides linked together. H,C-O OHO „OH OH А: НО НО A В: ОН (b) In the structure, circle the anomeric carbon of each saccharide. (c) Is each saccharide present in its a or ß anomer? Specify both A and B (d) Would this disaccharide undergo mutarotation? Why or why not? (e) Would this disaccharide react with Tollens and/or Benedicts reagent? Why or why not? (f) There are two reasons this is very unlikely to be a naturally occurring disaccharide. What about its structure suggests this is true? Give both reasons.arrow_forwardThe anticoagulant heparin is a polysaccharide that contains alternating residues of -D- glucuronic acid-6- sulfate and N-sulfo-D-glucosamine-6sulfate connected by (1 B 4)- glycosidic linkages. Draw a part of heparin that shows one each of the two residues.arrow_forwardA 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_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_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_forwardTreatment with NaBH 4 converts aldose U into an optically inactive (meso) alditol V. Ruff degradation ofU gives W, whose alditol is optically inactive. Ruff degradation of W forms D-glyceraldehyde, thesimplest aldose. Upon Kiliani-Fischer synthesis, U is converted to two aldoses, X and Y. X is oxidized toan optically active aldaric acid Z. Y is oxidized to an optically inactive aldaric acid. Draw the structuresof D-glyceraldehyde, V, W, X, Y, and Z. Structure of compound U is shown below.arrow_forward
- Although reaction occurs in sugars also. H, OH H H-C-OH Oxidizing agent OH OH Н-С-ОН Н-С-ОН C=0 R OH R R R Aldose Aldonic acid anion Ketose Enediol Copyright © 2007 Pearson Prentice Hall, Inc. Draw the reaction above substituting D-fructose instead of the generalized ketose structure shown above (you need to draw all 4 structures). Slan and upload your drawing.arrow_forwardIdentify compounds A–D. A D-aldopentose A is oxidized with HNO3 to an optically inactive aldaric acid B. A undergoes the Kiliani–Fischer synthesis to yield C and D. C is oxidized to an optically active aldaric acid. D is oxidized to an optically inactive aldaric acidarrow_forwardPredict the products obtained when d-galactose reacts with each reagent. (h) NaBH4(i) Br2, H2O, then H2O2 and Fe2(SO4)3arrow_forward
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