Textbook Question
One of the following compounds undergoes electrophilic aromatic substitution predominantly at C-3, and one undergoes electrophilic aromatic substitution predominantly at C-4. Which is which?
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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 28
Bruice 8th EditionCh. 19 - More About Amines • Reactions of Heterocyclic CompoundsProblem 28Chapter 20, Problem 28
Pyrrole reacts with excess para-(N,N-dimethylamino)benzaldehyde to form a highly colored compound. Draw the structure of the colored compound.
Verified step by step guidance1
Understand the reaction: Pyrrole is a five-membered aromatic heterocycle with a nitrogen atom. It is highly reactive in electrophilic aromatic substitution reactions due to the electron-donating nature of the nitrogen atom. Para-(N,N-dimethylamino)benzaldehyde contains an electron-donating N,N-dimethylamino group and an aldehyde functional group, making it an electrophile in this reaction.
Recognize the reaction type: This is a condensation reaction, specifically a type of electrophilic aromatic substitution followed by a series of steps leading to the formation of a conjugated system. Pyrrole reacts with the aldehyde group of para-(N,N-dimethylamino)benzaldehyde to form a conjugated product.
Determine the mechanism: The reaction begins with the nucleophilic attack of the pyrrole on the carbonyl carbon of the aldehyde group. This forms an intermediate that undergoes dehydration (loss of water) to form a double bond, resulting in a conjugated imine structure.
Consider the excess reagent: Since excess para-(N,N-dimethylamino)benzaldehyde is used, multiple aldehyde molecules can react with pyrrole. This leads to the formation of a highly conjugated system, which is responsible for the intense coloration of the product.
Draw the final structure: The final product is a conjugated compound where pyrrole is linked to multiple para-(N,N-dimethylamino)benzaldehyde units through imine bonds. The extended conjugation and the electron-donating N,N-dimethylamino groups contribute to the compound's color.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Pyrrole Structure and Reactivity
Pyrrole is a five-membered aromatic heterocycle containing a nitrogen atom. Its structure allows for nucleophilic attack due to the electron-rich nature of the nitrogen, making it reactive towards electrophiles. Understanding pyrrole's reactivity is crucial for predicting its behavior in reactions, such as with para-(N,N-dimethylamino)benzaldehyde.
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Reactions of Pyrrole, Furan, and Thiophene Example 1
Electrophilic Aromatic Substitution
Electrophilic aromatic substitution (EAS) is a fundamental reaction mechanism in organic chemistry where an electrophile replaces a hydrogen atom on an aromatic ring. In this case, the para-(N,N-dimethylamino)benzaldehyde acts as an electrophile, and recognizing how EAS occurs helps in determining the structure of the resulting compound formed from pyrrole.
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Color in Organic Compounds
The color of organic compounds often arises from the presence of conjugated systems, where alternating double and single bonds allow for delocalization of electrons. This delocalization can absorb visible light, leading to the appearance of color. Understanding how conjugation affects the electronic structure is essential for predicting the color of the compound formed in this reaction.
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Related Practice
Textbook Question
Name the following:
a.
b.
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Textbook Question
Benzene undergoes electrophilic aromatic substitution reactions with aziridines in the presence of a Lewis acid such as AlCl3.
a. What are the major and minor products of the following reaction?
b. Would you expect epoxides to undergo similar reactions?
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Textbook Question
Name the following:
c.
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Textbook Question
Rank the following compounds from most reactive to least reactive in an electrophilic aromatic substitution reaction:
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Textbook Question
A tertiary amine reacts with hydrogen peroxide to form a tertiary amine oxide.
Tertiary amine oxides undergo a reaction similar to the Hofmann elimination reaction (Section 10.10), called a Cope elimination. In this reaction, a tertiary amine oxide, rather than a quaternary ammonium ion, undergoes elimination. A strong base is not needed for a Cope elimination because the amine oxide acts as its own base.
Does the Cope elimination have an alkene-like transition state or a carbanion-like transition state?
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