Organic Chemistry (8th Edition)
8th Edition
ISBN: 9780134042282
Author: Paula Yurkanis Bruice
Publisher: PEARSON
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Chapter 20, Problem 48P
Interpretation Introduction
Interpretation:
The two possible structures for the
Concept Introduction:
The Wohl-degradation is opposite of the Killiani-Fisher synthesis. It shortens an aldoses chain by one carbon. Hexoses are converted to pentoses and pentoses are converted to tetroses.
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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?
An 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.
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.)
Chapter 20 Solutions
Organic Chemistry (8th Edition)
Ch. 20.1 - Prob. 1PCh. 20.2 - Prob. 2PCh. 20.2 - Prob. 3PCh. 20.3 - Prob. 4PCh. 20.3 - Prob. 5PCh. 20.3 - Prob. 6PCh. 20.4 - Prob. 7PCh. 20.4 - Prob. 8PCh. 20.5 - Prob. 9PCh. 20.5 - Prob. 10P
Ch. 20.5 - Prob. 11PCh. 20.6 - Prob. 12PCh. 20.6 - Prob. 13PCh. 20.6 - Prob. 14PCh. 20.7 - Prob. 15PCh. 20.8 - Prob. 16PCh. 20.9 - Prob. 18PCh. 20.10 - Prob. 20PCh. 20.10 - Prob. 21PCh. 20.10 - Prob. 22PCh. 20.11 - Prob. 23PCh. 20.11 - Prob. 24PCh. 20.12 - Prob. 25PCh. 20.12 - Prob. 26PCh. 20.14 - Prob. 28PCh. 20.15 - Prob. 29PCh. 20.15 - Prob. 30PCh. 20.16 - Prob. 31PCh. 20.17 - Prob. 32PCh. 20.18 - Refer to Figure 20.5 to answer the following...Ch. 20 - Prob. 34PCh. 20 - Prob. 35PCh. 20 - Prob. 36PCh. 20 - Prob. 37PCh. 20 - Prob. 38PCh. 20 - Prob. 39PCh. 20 - Prob. 40PCh. 20 - Prob. 41PCh. 20 - Prob. 42PCh. 20 - Prob. 43PCh. 20 - Prob. 44PCh. 20 - Prob. 45PCh. 20 - Prob. 46PCh. 20 - Prob. 47PCh. 20 - Prob. 48PCh. 20 - The 1H NMR spectrum of D-glucose in D2O exhibits...Ch. 20 - Prob. 50PCh. 20 - Prob. 51PCh. 20 - Prob. 52PCh. 20 - Prob. 53PCh. 20 - Prob. 54PCh. 20 - Prob. 55PCh. 20 - Prob. 56PCh. 20 - Prob. 57PCh. 20 - Prob. 58PCh. 20 - Prob. 59PCh. 20 - Prob. 60PCh. 20 - Prob. 61PCh. 20 - A hexose is obtained when the residue of a shrub...Ch. 20 - Prob. 63PCh. 20 - Prob. 64PCh. 20 - Prob. 65PCh. 20 - Prob. 66PCh. 20 - Prob. 67PCh. 20 - Prob. 68PCh. 20 - Prob. 69PCh. 20 - Prob. 70PCh. 20 - Prob. 71PCh. 20 - Prob. 72PCh. 20 - Prob. 73P
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- When an optically active D-aldopentose was subjected to Kiliani-Fischer synthesis, followed by NaBH4/H2O, it produced a mixture of an optically active and an optically inactive alditol. When the same D-aldopentose was subjected to Wohl degradation followed by HNO3 it produced an optically inactive aldaric acid. Provide the structure of this D-aldopentose. Н- НО- н- H -ОН НО -H Н- -Н CH₂OH 1 A) 1 B) II C) III осн H D) IV НО осн -H Н- -OH H- H HỌ CH₂OH П -OH H -OH H Н -H CH₂OH Ш _H -OH HO -OH H- -OH H- осн -H -OH CH₂OH IV -OH CH₂OH Varrow_forwardIllustrate the treatment of methyl α-D-glucopyranoside with aqueous acid forms a mixture of α- and β-D-glucose and methanol ?arrow_forwardCarbohydrates 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_forward
- Which D-aldopentoses are reduced to optically inactive alditols using NaBH4, CH3OH?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 2-ketohexose is reduced with NABH4 in CH3OH to form a mixture of D-galactitol and D-talitol. What is the structure of the 2-ketohexose?arrow_forward
- The most stable conformation of the pyranose ring of most D-aldohexoses places the largest group, CH2OH, in the equatorial position. An exception to this is the aldohexose D-idose. Draw the two possible chair conformations of either the α or β anomer of D-idose. Explain why the more stable conformation has the CH2OH group in the axial position.arrow_forwardThe 1H NMR spectrum of d-glucose in D2O exhibits two high-frequency doublets. What is responsible for these doublets?arrow_forwardIn 1891, Emil Fischer determined the structures of glucose and the seven other d-aldohexoses using only simple chemical reactions and clever reasoning about stereochemistry andsymmetry. He received the Nobel Prize for this work in 1902. Fischer had determined thatd-glucose is an aldohexose, and he used Ruff degradations to degrade it to (+)-glyceraldehyde. Therefore, the eight d-aldohexose structures shown in Figure 23-3 are the possiblestructures for glucose.Pretend that no names are shown in Figure 23-3 except for glyceraldehyde, and usethe following results to prove which of these structures represent glucose, mannose,arabinose, and erythrose.(a) Upon Ruff degradation, glucose and mannose give the same aldopentose: arabinose.Nitric acid oxidation of arabinose gives an optically active aldaric acid. What are thetwo possible structures of arabinose?(b) Upon Ruff degradation, arabinose gives the aldotetrose erythrose. Nitric acid oxidation of erythrose gives an optically inactive…arrow_forward
- In 1891, Emil Fischer determined the structures of glucose and the seven other d-aldohexoses using only simple chemical reactions and clever reasoning about stereochemistry andsymmetry. He received the Nobel Prize for this work in 1902. Fischer had determined thatd-glucose is an aldohexose, and he used Ruff degradations to degrade it to (+)-glyceraldehyde. Therefore, the eight d-aldohexose structures shown in Figure 23-3 are the possiblestructures for glucose.Pretend that no names are shown in Figure 23-3 except for glyceraldehyde, and usethe following results to prove which of these structures represent glucose, mannose,arabinose, and erythrose.(a) Upon Ruff degradation, glucose and mannose give the same aldopentose: arabinose.Nitric acid oxidation of arabinose gives an optically active aldaric acid. What are thetwo possible structures of arabinose?(b) Upon Ruff degradation, arabinose gives the aldotetrose erythrose. Nitric acid oxidation of erythrose gives an optically inactive…arrow_forwardList all possible D-2-ketohexoses. One of these D-2-ketohexoses is called sorbose. When sorbose is treated with sodium borohydride it produces a mixture of glucitol and iditol. What is the structure of sorbose? Another D-2-ketohexose, psychosa produces a mixture of alitol and altritol when reduced with sodium borohydride, which is the structure of psychosearrow_forwardChoose the product that is expected when the β-pyranose form of compound A is treated with excess ethyl iodide in the presence of silver oxide. The following information can be used to determine the identity of compound A: 1. The molecular formula of compound A is C6H12O6.2. Compound A is a reducing sugar.3. When compound A is subjected to a Wohl degradation two times sequentially, D-erythrose is obtained.4. Compound A is epimeric with D-glucose at C3.5. The configuration at C2 is R.arrow_forward
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