Textbook Question
Explain why cyclopentadiene (pKa = 15) is more acidic than pyrrole (pKa ∼17), even though nitrogen is more electronegative than carbon.
Ch. 19 - More About Amines • Reactions of Heterocyclic Compounds
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. 19 - More About Amines • Reactions of Heterocyclic CompoundsProblem 5d
Bruice 8th EditionCh. 19 - More About Amines • Reactions of Heterocyclic CompoundsProblem 5dChapter 20, Problem 5d
Draw the product of each of the following reactions:
d. 
Verified step by step guidance1
Step 1: Identify the reactants. The left structure is a ketone (2-pentanone), and the right structure is an amine (ethylamine). The reaction occurs in the presence of HCl, which acts as a catalyst.
Step 2: Recognize the type of reaction. This is an imine formation reaction, where a ketone reacts with a primary amine under acidic conditions to form an imine.
Step 3: Understand the mechanism. The ketone undergoes nucleophilic attack by the amine, forming a tetrahedral intermediate. Protonation and dehydration follow, leading to the formation of the imine.
Step 4: Predict the product structure. Replace the oxygen of the ketone with the nitrogen from the amine, and attach the ethyl group to the nitrogen. The double bond forms between the carbon and nitrogen.
Step 5: Verify the stereochemistry and connectivity. Ensure the carbon-nitrogen double bond is correctly placed, and the ethyl group is bonded to the nitrogen atom in the final imine product.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Imine Formation
Imine formation occurs when a carbonyl compound, such as an aldehyde or ketone, reacts with an amine. The reaction involves the nucleophilic attack of the amine on the carbonyl carbon, leading to the formation of a tetrahedral intermediate. This intermediate then loses a water molecule, resulting in the formation of an imine, characterized by a C=N bond.
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Imine Mechanism
Enamine Formation
Enamines are formed when a carbonyl compound reacts with a secondary amine. Similar to imine formation, the amine attacks the carbonyl carbon, forming a tetrahedral intermediate. However, in this case, the intermediate undergoes dehydration to yield an enamine, which features a C=C bond adjacent to a nitrogen atom, providing unique reactivity in organic synthesis.
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Role of HCl in Reactions
Hydrochloric acid (HCl) serves as a catalyst in the formation of imines and enamines by protonating the carbonyl oxygen. This protonation increases the electrophilicity of the carbonyl carbon, facilitating the nucleophilic attack by the amine. Additionally, HCl can help drive the dehydration step, promoting the formation of the final imine or enamine product.
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Related Practice
Textbook Question
When pyrrole is added to a dilute solution of D2SO4 in D2O, 2-deuteriopyrrole is formed. Propose a mechanism to account for the formation of this compound.
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Textbook Question
Draw the product formed when pyridine reacts with ethyl bromide
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Textbook Question
Draw the product of each of the following reactions:
b.
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Name the following:
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Textbook Question
Why is the conjugate acid of morpholine more acidic than the conjugate acid of piperidine?
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