Domanda del libro di testo
(a) The isoelectric point (pI) of phenylalanine is pH 5.5. Draw the structure of the major form of phenylalanine at pH values of 1, 5.5, and 11.
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Ch. 24 - Amino Acids, Peptides, and Proteins
Wade9th EditionOrganic ChemistryISBN: 9780135213728
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TOC.tableOfContents
- Ch.1 - Structure and Bonding107
- Ch. 2 - Acids and Bases; Functional Groups115
- Ch.3 - Structure and Stereochemistry of Alkanes100
- Ch.4 - The Study of Chemical Reactions99
- Ch.5 - Stereochemistry93
- Ch.6 - Alkyl Halides; Nucleophilic Substitution118
- Ch. 7 - Structure and Synthesis of Alkenes; Elimination158
- Ch.8 - Reactions of Alkenes171
- Ch.9 - Alkynes91
- Ch.10 - Structure and Synthesis of Alcohols143
- Ch.11 - Reactions of Alcohols104
- Ch. 12 - Infrared Spectroscopy and Mass Spectrometry22
- Ch. 13 - Nuclear Magnetic Resonance Spectroscopy45
- Ch. 14 - Ethers, Epoxides, and Thioethers72
- Ch. 15 - Conjugated Systems, Orbital Symmetry, and Ultraviolet Spectroscopy89
- Ch. 16 - Aromatic Compounds74
- Ch. 17 - Reactions of Aromatic Compounds126
- Ch. 18 - Ketones and Aldehydes193
- Ch. 19 - Amines129
- Ch. 20 - Carboxylic Acids77
- Ch. 21 - Carboxylic Acid Derivatives141
- Ch. 22 - Condensations and Alpha Substitutions of Carbonyl Compounds175
- Ch. 23 - Carbohydrates and Nucleic Acids93
- Ch. 24 - Amino Acids, Peptides, and Proteins54
Capitolo 24, Problema 24a
Propose a mechanism for the coupling of acetic acid and aniline using DCC as a coupling agent.
Guida verificata passo dopo passo1
Identify the role of DCC (dicyclohexylcarbodiimide) in the reaction: DCC is a coupling agent that activates the carboxylic acid group of acetic acid, making it more reactive toward nucleophilic attack by the amine group of aniline.
Step 1: Activation of acetic acid by DCC. The lone pair of electrons on the oxygen atom of the carboxylic acid group in acetic acid attacks the carbon atom of the carbodiimide group in DCC, forming an O-acylisourea intermediate. This intermediate is highly reactive and facilitates the coupling reaction.
Step 2: Nucleophilic attack by aniline. The lone pair of electrons on the nitrogen atom of aniline attacks the carbonyl carbon of the O-acylisourea intermediate, forming a tetrahedral intermediate.
Step 3: Collapse of the tetrahedral intermediate. The tetrahedral intermediate collapses, leading to the formation of the amide bond between acetic acid and aniline, and dicyclohexylurea (DCU) as a byproduct.
Step 4: Final product formation. The reaction results in the formation of acetanilide (an amide) as the final product, along with DCU, which can be removed by filtration due to its insolubility in many solvents.
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Concetti chiave
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Coupling Reactions
Coupling reactions involve the formation of a new bond between two molecules, typically involving a nucleophile and an electrophile. In this context, acetic acid acts as a carboxylic acid nucleophile, while aniline serves as an amine nucleophile. Understanding the nature of these reactants and their reactivity is crucial for proposing a mechanism.
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02:54
Sonogashira Coupling Reaction
DCC (Dicyclohexylcarbodiimide)
DCC is a commonly used coupling agent in organic synthesis that facilitates the formation of amide bonds between carboxylic acids and amines. It activates the carboxylic acid by converting it into a more reactive intermediate, allowing for the nucleophilic attack by the amine. Familiarity with DCC's role and mechanism is essential for understanding how it aids in the coupling of acetic acid and aniline.
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02:32Synthesis of Amides
Mechanism of Amide Formation
The mechanism of amide formation typically involves the nucleophilic attack of an amine on the activated carboxylic acid. In the presence of DCC, the carboxylic acid forms an O-acylurea intermediate, which is then attacked by the amine, leading to the formation of the amide bond and the release of dicyclohexylurea as a byproduct. Understanding this stepwise process is vital for accurately proposing the overall reaction mechanism.
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01:33Amide Nomenclature
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