Textbook Question
Draw the pH–activity profile for an enzyme that has one catalytic group at the active site:
a. the catalytic group is a general-acid catalyst with a pKa = 5.6.
2
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Ch. 22 - Catalysis in Organic Reactions and in Enzymatic Reactions
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
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Bruice 8th EditionCh. 22 - Catalysis in Organic Reactions and in Enzymatic ReactionsProblem 15
Bruice 8th EditionCh. 22 - Catalysis in Organic Reactions and in Enzymatic ReactionsProblem 15Chapter 23, Problem 15
Which of the following amino acid side chains can help remove a proton from the α-carbon of an aldehyde?
Verified step by step guidance1
Step 1: Analyze the chemical structures provided in the image. The side chains correspond to amino acids: Structure 1 is glycine, Structure 2 is phenol (tyrosine-like), Structure 3 is imidazole (histidine-like), and Structure 4 is a carboxylate group (glutamate-like).
Step 2: Recall that removing a proton from the α-carbon of an aldehyde requires a base. A base is a molecule or functional group capable of accepting a proton, typically having lone pairs or negative charge.
Step 3: Evaluate the side chains for their ability to act as bases. Structure 3 (imidazole) contains a nitrogen atom with lone pairs, making it a good candidate for proton abstraction. Structure 4 (carboxylate) also has a negatively charged oxygen, which can act as a base.
Step 4: Consider the pKa values of the functional groups. Imidazole has a pKa around 6, making it effective at physiological pH for proton abstraction. Carboxylate groups are also deprotonated at physiological pH, making them strong bases.
Step 5: Conclude that the side chains in Structure 3 (imidazole) and Structure 4 (carboxylate) are capable of removing a proton from the α-carbon of an aldehyde due to their basic properties.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Amino Acid Structure
Amino acids are organic compounds that serve as the building blocks of proteins. Each amino acid consists of a central carbon atom (the alpha carbon) bonded to an amino group, a carboxyl group, a hydrogen atom, and a variable side chain (R group). The properties of the side chain determine the amino acid's characteristics and its role in biochemical reactions.
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Charged Amino Acids
Acid-Base Chemistry
Acid-base chemistry involves the transfer of protons (H+) between molecules. In this context, an amino acid can act as a base if its side chain has a functional group capable of accepting a proton. Understanding the pKa values of these side chains is crucial, as it indicates their ability to donate or accept protons under physiological conditions.
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02:49The Lewis definition of acids and bases.
Reactivity of Aldehydes
Aldehydes are organic compounds characterized by a carbonyl group (C=O) bonded to at least one hydrogen atom. They are reactive due to the electrophilic nature of the carbon atom in the carbonyl group, making them susceptible to nucleophilic attack. Certain amino acid side chains can facilitate the removal of a proton from the alpha carbon of an aldehyde, influencing the reactivity and stability of the compound.
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Related Practice
Textbook Question
Draw the pH–activity profile for an enzyme that has one catalytic group at the active site:
b. the catalytic group is a general-base catalyst with a pKa = 7.2.
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Textbook Question
The relative rate of reaction for the cis alkene (E) is given in Table 22.2. What do you expect the relative rate of reaction for the trans alkene to be?
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Textbook Question
Which of the following C-terminal peptide bonds is more readily cleaved by carboxypeptidase A? Explain your choice.
Ser-Ala-Leu or Ser-Ala-Asp
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Textbook Question
Why do the nitro groups change the relative leaving tendencies of the carboxy and 2,4-dinitrophenoxy groups in the tetrahedral intermediate in Problem 11?
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Textbook Question
Show all the products, including their configurations, that are obtained from the above reaction.
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