18-53 In Chapter 27, we will study a metabolic pathway called the tricarboxylic acid cycle (TCA), also known as the citric acid or Krebs cycle. We have already seen examples of most of the reactions in this pathway. Following is an outline of the pathway beginning with the molecule for which the pathway is named. A particular enzyme that is highly speci?c catalyzes each of these reactions. Each enzyme-catalyzed reaction gives a high yield of the target molecule. (a) Which of these TCA-cycle intermediates are chiral? Which intermediate has the greatest number of chiral centers? Which intermediates show cis-trans isomerism? (b) Name the type of reaction that takes place in Steps 1-3. (c) Notice that the hydration of aconitic acid to give isocitric acid does not follow Markovnikov’s rule. If the hydration of aconitic acid were to follow Markovnikov’s rule, what product would be formed? Offer an explanation for the formation of this non-Markovnikov product. (d) What type of reactions take place in Steps 4-8? (e) The only reaction we have not studied is Step 5. Because it involves a loss of CO 2 , it is classi?ed as a decarboxylation. Show that it also involves oxidation. Because it involves both oxidation and decarboxylation, it is classi?ed as an oxidative decarboxylation. (f) Reaction 4 is also classi?ed as a decarboxylation. Does this decarboxylation also involve an oxidation?

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Introduction to General, Organic a...

11th Edition
Frederick A. Bettelheim + 4 others
Publisher: Cengage Learning
ISBN: 9781285869759
BuyFind

Introduction to General, Organic a...

11th Edition
Frederick A. Bettelheim + 4 others
Publisher: Cengage Learning
ISBN: 9781285869759

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Chapter 18, Problem 18.53P
Textbook Problem

18-53 In Chapter 27, we will study a metabolic pathway called the tricarboxylic acid cycle (TCA), also known as the citric acid or Krebs cycle. We have already seen examples of most of the reactions in this pathway. Following is an outline of the pathway beginning with the molecule for which the pathway is named. A particular enzyme that is highly speci?c catalyzes each of these reactions. Each enzyme-catalyzed reaction gives a high yield of the target molecule.

Chapter 18, Problem 18.53P, 18-53 In Chapter 27, we will study a metabolic pathway called the tricarboxylic acid cycle (TCA),

(a) Which of these TCA-cycle intermediates are chiral? Which intermediate has the greatest number of chiral centers? Which intermediates show cis-trans isomerism?

(b) Name the type of reaction that takes place in Steps 1-3.

(c) Notice that the hydration of aconitic acid to give isocitric acid does not follow Markovnikov’s rule. If the hydration of aconitic acid were to follow Markovnikov’s rule, what product would be formed? Offer an explanation for the formation of this non-Markovnikov product.

(d) What type of reactions take place in Steps 4-8?

(e) The only reaction we have not studied is Step 5. Because it involves a loss of CO2, it is classi?ed as a decarboxylation. Show that it also involves oxidation. Because it involves both oxidation and decarboxylation, it is classi?ed as an oxidative decarboxylation.

(f) Reaction 4 is also classi?ed as a decarboxylation. Does this decarboxylation also involve an oxidation?

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Chapter 18 Solutions

Introduction to General, Organic and Biochemistry
Ch. 18 - 18-11 Draw a structural formula for each...Ch. 18 - 18-12 Calcium oxalate is a major component of...Ch. 18 - 18-13 The monopotassium salt of oxalic acid is...Ch. 18 - 18-14 Answer true or false. (a) Carboxylic acids...Ch. 18 - 18-15 Draw a structural formula for the dimer...Ch. 18 - 18-16 Propanedioic (malonic) acid forms an...Ch. 18 - 18-17 Hexanoic (caproic) acid has a solubility in...Ch. 18 - 18-18 Propanoic acid and methyl acetate are...Ch. 18 - 18-19 The following compounds have approximately...Ch. 18 - 18-20 The following compounds have approximately...Ch. 18 - 18-21 Arrange these compounds in order of...Ch. 18 - 18-22 Answer true or false. (a) Fatty acids are...Ch. 18 - 18-23 Characterize the structural features...Ch. 18 - 18-24 The detergents illustrated in this chapter...Ch. 18 - 18-25 Following are structural formulas for two...Ch. 18 - 18-26 Answer true or false. (a) Carboxylic acids...Ch. 18 - 18-27 Alcohols, phenols, and carboxylic acids all...Ch. 18 - 18-28 Arrange these compounds in order of...Ch. 18 - 18-29 Complete the equations for these acid—base...Ch. 18 - 18-30 Complete the equations for these acid-base...Ch. 18 - 18-31 Formic acid is one of the components...Ch. 18 - 18-32 Starting with the definition of Ka of a weak...Ch. 18 - 18-33 Using the equation from Problem 18-32 that...Ch. 18 - 18-34 The pKa of acetic acid is 4.75. What form(s)...Ch. 18 - 18-35 The normal pH range for blood plasma is 7.35...Ch. 18 - 18-36 The pKa of ascorbic acid (Vitamin C, see...Ch. 18 - 18-37 Complete the equations for the following...Ch. 18 - 18-38 Which is the stronger base: CH3CH2NH2 or...Ch. 18 - 18-39 Complete the equations for the following...Ch. 18 - 18-40 Define and give an example of Fischer...Ch. 18 - 18-41 Complete these examples of Fischer...Ch. 18 - 18-42 From what carboxylic acid and alcohol is...Ch. 18 - 18-43 Methyl 2-hydroxybenzoate (methyl salicylate)...Ch. 18 - 18-44 Show how you could convert cinnamic acid to...Ch. 18 - 18-45 Give the expected organic product formed...Ch. 18 - 18-46 Procaine (its hydrochloride salt is marketed...Ch. 18 - 18-47 Methylparaben and propylparaben are used as...Ch. 18 - 18-48 4-Aminobenzoic acid is prepared from benzoic...Ch. 18 - 18-49 When 5-hydroxypentanoic acid is treated with...Ch. 18 - 18-50 We have seen that esters can be prepared by...Ch. 18 - 18-51 Draw the structural formula of a compound...Ch. 18 - 18-52 Complete the equations for these oxidations:Ch. 18 - 18-53 In Chapter 27, we will study a metabolic...Ch. 18 - 18-54 Azithromycin is a broad-spectrum antibiotic...Ch. 18 - 18-55 Below is the structural formula of a...

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