Textbook Question
The following molecules and ions are grouped by similar structures. Classify each as aromatic, antiaromatic, or nonaromatic. For the aromatic and antiaromatic species, give the number of pi electrons in the ring.
(a)
1
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Ch. 16 - Aromatic Compounds
Wade9th EditionOrganic ChemistryISBN: 9780135213728
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Table of contents
- 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
Chapter 16, Problem 30
One of the following hydrocarbons is much more acidic than the others. Indicate which one, and explain why it is unusually acidic.
Verified step by step guidance1
Step 1: Analyze the structures of the hydrocarbons provided in the image. Each structure contains a five-membered ring with varying substituents. Pay attention to the presence of double bonds and the type of substituents attached to the ring.
Step 2: Recall that acidity in hydrocarbons is influenced by the stability of the conjugate base formed after deprotonation. A more stable conjugate base corresponds to a more acidic compound.
Step 3: Examine the substituents on the ring. In structure C, the substituent is an electron-withdrawing carbonyl group (C=O). Electron-withdrawing groups stabilize the negative charge on the conjugate base through resonance or inductive effects.
Step 4: Compare the other structures (A, B, and D). These structures lack electron-withdrawing groups like the carbonyl group in C. Their conjugate bases are less stabilized, making them less acidic.
Step 5: Conclude that structure C is unusually acidic due to the presence of the carbonyl group, which stabilizes the conjugate base through resonance and inductive effects, making it much more acidic than the other hydrocarbons.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Acidity of Hydrocarbons
The acidity of hydrocarbons is determined by their ability to donate protons (H+ ions). In organic chemistry, the presence of electronegative atoms or groups can stabilize the negative charge of the conjugate base formed after deprotonation, thus increasing acidity. Aromatic compounds often exhibit unique acidity due to resonance stabilization.
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Aromatic hydrocarbon acidity
Resonance Stabilization
Resonance stabilization occurs when a molecule can be represented by multiple valid Lewis structures, allowing for the delocalization of electrons. This delocalization can stabilize the negative charge on a conjugate base, making the corresponding acid more acidic. In aromatic compounds, resonance can significantly influence acidity by distributing charge over the aromatic system.
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Aromaticity
Aromaticity refers to the enhanced stability of cyclic compounds with conjugated pi electron systems that follow Huckel's rule (4n + 2 pi electrons). Aromatic compounds are often more stable than their non-aromatic counterparts, which can affect their reactivity and acidity. The unique electronic structure of aromatic compounds can lead to unusual acidity patterns among different hydrocarbons.
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Related Practice
Textbook Question
Four pairs of compounds are shown. In each pair, one of the compounds reacts more quickly, or with a more favorable equilibrium constant, than the less conjugated system. In each case, explain the enhanced reactivity.
(d)
2
views
Textbook Question
The following molecules and ions are grouped by similar structures. Classify each as aromatic, antiaromatic, or nonaromatic. For the aromatic and antiaromatic species, give the number of pi electrons in the ring.
(c)
4
views
Textbook Question
The following molecules and ions are grouped by similar structures. Classify each as aromatic, antiaromatic, or nonaromatic. For the aromatic and antiaromatic species, give the number of pi electrons in the ring.
(b)
Textbook Question
Four pairs of compounds are shown. In each pair, one of the compounds reacts more quickly, or with a more favorable equilibrium constant, than the less conjugated system. In each case, explain the enhanced reactivity.
(a)
(b)
1
views
Textbook Question
Four pairs of compounds are shown. In each pair, one of the compounds reacts more quickly, or with a more favorable equilibrium constant, than the less conjugated system. In each case, explain the enhanced reactivity.
(c)
2
views