Concept explainers
Interpretation:
The structures of D-xylose and D-lyxose are to be drawn.
Concept Introduction:
Carbohydrates are naturally occurring organic compounds. As the name implies carbohydrates are hydrates of carbon and have general formula of
Sugars are classified by the number of carbon atoms and functional group they contains. The monosaccharide glucose is called an Aldohexose as it contains six carbon atoms as well as an aldehyde functional group and fructose is known as ketohexose as it contains six carbons with a ketone functional group. Similarly, D-threose contain four carbon atom in a chain.
In Killiani-Fisher synthesis, hydrogen cyanide attacks the carbonyl group. The carbonyl carbon is converted to an asymmetric center. The
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Organic Chemistry
- A hexose was obtained after (+)-glyceraldehyde underwent three successive Kiliani–Fischer syntheses. Identify the hexose from the following experimental information: oxidation with nitric acid forms an optically active aldaric acid; a Wohl degradation followed by oxidation with nitric acid forms an optically inactive aldaric acid; and a second Wohl degradation forms erythrose.arrow_forwardd-Altrose is an aldohexose. Ruff degradation of d-altrose gives the same aldopentose asdoes degradation of d-allose, the C3 epimer of glucose. Give the structure of d-altrosearrow_forwardSugar 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 Xarrow_forward
- An unknown reducing disaccharide is found to be unaffected by invertase enzymes. Treatment with an a@galactosidasecleaves the disaccharide to give one molecule of d-fructose and one molecule of d-galactose. When the disaccharideis treated with excess iodomethane and silver oxide and then hydrolyzed in dilute acid, the products are2,3,4,6-tetra-O-methylgalactose and 1,3,4-tri-O-methylfructose. Propose a structure for this disaccharide, and give itscomplete systematic name.arrow_forwardAldohexoses 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 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_forward
- An unknown β-d-aldohexose has only one axial substituent. A Wohl degradation forms a compound which, when treated with sodium borohydride, forms an optically active alditol. This information allows you to arrive at two possible structures for the β-d-aldohexose. What experiment can you carry out to distinguish between the two possibilities?arrow_forwardWhich D-aldopentose is oxidized to an optically active aldaric acid and undergoes the Wohl degradation to yield a Daldotetrose that is oxidized to an optically active aldaric acid?arrow_forwardHow many stereoisomers are possible for an aldopentose?arrow_forward
- Mannose exists in aqueous solution as a mixture of a-d-mannopyranose and b-d-mannopyranose. Draw Haworth projections for these molecules.arrow_forwardWhat are the similarities and differences between the NMR of α-D-glucose and α-D-galactose?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 LearningEBK A SMALL SCALE APPROACH TO ORGANIC LChemistryISBN:9781305446021Author:LampmanPublisher:CENGAGE LEARNING - CONSIGNMENT