Textbook Question
The specific rotation of (R)-(+)-glyceraldehyde is +8.7. If the observed specific rotation of a mixture of (R)-glyceraldehyde and (S)-glyceraldehyde is +1.4, what percent of glyceraldehyde is present as the R enantiomer?
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Ch. 4 - Isomers: The Arrangement of Atoms in Space
Bruice8th EditionOrganic ChemistryISBN: 9780135213711
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Table of contents
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 1)31
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 2)65
- Ch. 2 - Acids and Bases: Central to Understanding Organic Chemistry84
- Ch. 3 - An Introduction to Organic Compounds:Nomenclature, Physical Properties, and Structure183
- Ch. 4 - Isomers: The Arrangement of Atoms in Space121
- Ch. 5 - Alkenes: Structure, Nomenclature, and an Introduction to Reactivity • Thermodynamics and Kinetics83
- Ch. 6 - The Reactions of Alkenes • The Stereochemistry of Addition Reactions175
- Ch. 7 - The Reactions of Alkynes • An Introduction to Multistep Synthesis119
- Ch. 8 - Delocalized Electrons: Their Effect on Stability, pKa, and the Products of a Reaction • Aromaticity and Electronic Effects: An Introduction to the Reactions of Benzene148
- Ch. 9 - Substitution and Elimination Reactions of Alkyl Halides212
- Ch. 10 - Reactions of Alcohols, Ethers, Epoxides, Amines, and Sulfur-Containing Compounds131
- Ch. 11 - Organometallic Compounds60
- Ch. 12 - Radicals90
- Ch. 13 - Mass Spectrometry; Infrared Spectroscopy; UV/Vis Spectroscopy62
- Ch. 14 - NMR Spectroscopy95
- Ch. 15 - Reactions of Carboxylic Acids and Carboxylic Acid Derivatives123
- Ch. 16 - Reactions of Aldehydes and Ketones • More Reactions of Carboxylic Acid Derivatives141
- Ch. 17 - Reactions at the Alpha-Carbon101
- Ch. 18 - Reactions of Benzene and Substituted Benzenes144
- Ch. 19 - More About Amines • Reactions of Heterocyclic Compounds49
- Ch. 20 - The Organic Chemistry of Carbohydrates80
- Ch. 21 - Amino Acids, Peptides, and Proteins57
- Ch. 22 - Catalysis in Organic Reactions and in Enzymatic Reactions35
- Ch. 23 - The Organic Chemistry of the Coenzymes—Compounds Derived from Vitamins1
- Ch. 28 - Pericyclic Reactions58
Chapter 5, Problem 80b
Citrate synthase, one of the enzymes in the series of enzyme-catalyzed reactions known as the citric acid cycle, catalyzes the synthesis of citric acid from oxaloacetic acid and acetyl-CoA. If the synthesis is carried out with acetyl-CoA that contains radioactive carbon (14C) in the indicated position, the isomer shown here is obtained.
b. If the acetyl-CoA used in the synthesis contains 12C instead of 14C, will the product of the reaction be chiral or achiral?
Verified step by step guidance1
Step 1: Understand the reaction mechanism. Citrate synthase catalyzes the reaction between oxaloacetic acid and acetyl-CoA to form citric acid. The acetyl group from acetyl-CoA is added to oxaloacetic acid, forming a new carbon-carbon bond.
Step 2: Analyze the chirality of the product. Chirality arises when a molecule has a carbon atom bonded to four different groups, making it asymmetric. In the case of citric acid, the chirality depends on the arrangement of substituents around the carbon atoms.
Step 3: Consider the isotopic substitution. If acetyl-CoA contains radioactive carbon (14C), the product will have a labeled carbon atom, which can affect the symmetry of the molecule. However, if acetyl-CoA contains 12C instead of 14C, the molecule's symmetry remains unchanged.
Step 4: Evaluate the symmetry of the product. Citric acid is inherently achiral because it has a plane of symmetry. The substitution of 12C does not introduce asymmetry, so the product remains achiral.
Step 5: Conclude the chirality of the product. When acetyl-CoA contains 12C, the product of the reaction will be achiral, as the molecule retains its symmetry and does not have any asymmetric carbon centers.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Chirality
Chirality refers to the geometric property of a molecule that makes it non-superimposable on its mirror image, much like left and right hands. A chiral molecule typically has at least one carbon atom bonded to four different substituents, resulting in two distinct enantiomers. Understanding chirality is crucial in organic chemistry, especially in the context of biological systems where the activity of molecules can differ significantly between enantiomers.
Acetyl-CoA
Acetyl-CoA is a central metabolite in cellular metabolism, serving as a key substrate in the citric acid cycle. It is formed from the breakdown of carbohydrates, fats, and proteins and is essential for the synthesis of fatty acids and the production of energy. The presence of isotopes like 14C in acetyl-CoA can be used in tracing experiments to study metabolic pathways and the fate of carbon atoms in biochemical reactions.
Isomerism
Isomerism is the phenomenon where two or more compounds have the same molecular formula but different structural arrangements or spatial orientations. In organic chemistry, isomers can be classified as structural isomers, which differ in the connectivity of atoms, or stereoisomers, which differ in the orientation of atoms in space. The question of whether the product is chiral or achiral relates to the type of isomerism present in the synthesized compound, particularly in the context of the arrangement of substituents around chiral centers.
Related Practice
Textbook Question
A solution of an unknown compound (3.0 g of the compound in 200 mL of solution), when placed in a polarimeter tube 2.0 dm long, was found to rotate the plane of polarized light 18° in a counterclockwise direction. What is the specific rotation of the compound?
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Textbook Question
Which of the following has an achiral stereoisomer?
i. 1,2-dimethylcyclopentane
j, 1,2-dimethylcyclobutane
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Textbook Question
Are the following pairs identical, enantiomers, diastereomers, or constitutional isomers?
c.
d.
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Textbook Question
Are the following pairs identical, enantiomers, diastereomers, or constitutional isomers?
a.
b.
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Textbook Question
Citrate synthase, one of the enzymes in the series of enzyme-catalyzed reactions known as the citric acid cycle, catalyzes the synthesis of citric acid from oxaloacetic acid and acetyl-CoA. If the synthesis is carried out with acetyl-CoA that contains radioactive carbon (14C) in the indicated position, the isomer shown here is obtained.
a. Which stereoisomer of citric acid is synthesized: R or S?
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