Organic Chemistry
9th Edition
ISBN: 9781305080485
Author: John E. McMurry
Publisher: Cengage Learning
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Chapter 29.SE, Problem 24MP
One of the steps in the pentose phosphate pathway for glucose catabolism is the reaction of xylulose 5-phosphate with ribose 5-phosphate in the presence of a transketolase to give glyceraldehyde 3-phosphate and sedoheptulose 7-phosphate.
(a) The first part of the reaction is nucleophilic addition of thiamin diphosphate (TPP) ylide to xylulose 5-phosphate, followed by a retro-aldol cleavage to give glyceraldehyde 3-phosphate and a TPPcontaining enamine. Show the structure of the enamine and the mechanism by which it is formed.
(b) The second part of the reaction is addition of the enamine to ribose 5-phosphate followed by loss of TPP ylide to give sedoheptulose 7-phosphate. Show the mechanism.
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(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?
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.
Chapter 29 Solutions
Organic Chemistry
Ch. 29.1 - Prob. 1PCh. 29.3 - Write the equations for the remaining passages of...Ch. 29.3 - Prob. 3PCh. 29.4 - Write a mechanism for the dehydration reaction of...Ch. 29.4 - Evidence for the role of acetate in fatty-acid...Ch. 29.4 - Does the reduction of acetoacetyl ACP in step 6...Ch. 29.5 - Prob. 7PCh. 29.5 - Look at the entire glycolysis pathway, and make a...Ch. 29.6 - Prob. 9PCh. 29.7 - Prob. 10P
Ch. 29.7 - Write mechanisms for step 2 of the citric acid...Ch. 29.7 - Prob. 12PCh. 29.8 - Prob. 13PCh. 29.9 - Write all the steps in the transamination reaction...Ch. 29.9 - What -keto acid is formed on transamination of...Ch. 29.9 - Prob. 16PCh. 29.SE - Prob. 17VCCh. 29.SE - Identify the following intermediate in the citric...Ch. 29.SE - The following compound is an intermediate in the...Ch. 29.SE - Prob. 20VCCh. 29.SE - In the pentose phosphate pathway for degrading...Ch. 29.SE - Prob. 22MPCh. 29.SE - One of the steps in the pentose phosphate pathway...Ch. 29.SE - One of the steps in the pentose phosphate pathway...Ch. 29.SE - Prob. 25MPCh. 29.SE - Prob. 26MPCh. 29.SE - Prob. 27MPCh. 29.SE - Prob. 28MPCh. 29.SE - Prob. 29MPCh. 29.SE - Prob. 30MPCh. 29.SE - Prob. 31MPCh. 29.SE - Prob. 32APCh. 29.SE - Prob. 33APCh. 29.SE - Prob. 34APCh. 29.SE - Prob. 35APCh. 29.SE - Prob. 36APCh. 29.SE - Prob. 37APCh. 29.SE - Prob. 38APCh. 29.SE - Prob. 39APCh. 29.SE - Prob. 40APCh. 29.SE - Prob. 41APCh. 29.SE - Prob. 42APCh. 29.SE - Prob. 43APCh. 29.SE - Prob. 44APCh. 29.SE - Prob. 45APCh. 29.SE - Prob. 46APCh. 29.SE - Prob. 47APCh. 29.SE - Prob. 48APCh. 29.SE - Prob. 49APCh. 29.SE - Prob. 50APCh. 29.SE - In glycerol metabolism, the oxidation of...Ch. 29.SE - Prob. 52APCh. 29.SE - Prob. 53APCh. 29.SE - Prob. 54APCh. 29.SE - In step 7 of fatty-acid biosynthesis (Figure...Ch. 29.SE - Prob. 56AP
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