Textbook Question
Draw the structure of each compound.
(m) p-toluenesulfonic acid
(n) o-xylene
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 29a,b
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) 
Verified step by step guidance1
Step 1: Analyze the conjugation in the first pair of compounds. The compound on the left has a conjugated system due to the presence of alternating double bonds in the ring, which allows for delocalization of electrons. This delocalization increases the stability of the compound and enhances its basicity compared to the non-conjugated compound on the right.
Step 2: Consider the resonance effects in the first pair. The conjugated system on the left can stabilize the negative charge formed when the compound acts as a base, making it more favorable for the compound to accept a proton. The compound on the right lacks this resonance stabilization, making it less basic.
Step 3: For the second pair of compounds, examine the ionization process. The compound on the left has a conjugated system that allows for resonance stabilization of the positive charge formed after ionization. This stabilization makes ionization more favorable compared to the non-conjugated compound on the right.
Step 4: Evaluate the role of the chlorine atom in the second pair. The chlorine atom is an electron-withdrawing group, which can stabilize the positive charge formed during ionization. In the conjugated system on the left, the electron-withdrawing effect of chlorine is complemented by resonance stabilization, further enhancing ionization.
Step 5: Summarize the enhanced reactivity. In both pairs, the conjugated systems exhibit increased reactivity due to resonance stabilization, which either enhances basicity (first pair) or facilitates ionization (second pair). The lack of conjugation in the non-conjugated systems reduces their reactivity.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Conjugation
Conjugation refers to the overlap of p-orbitals across adjacent double bonds or lone pairs, allowing for delocalization of electrons. This delocalization stabilizes the molecule and can enhance its reactivity by lowering the energy barrier for reactions. In organic compounds, conjugated systems often exhibit increased stability and reactivity compared to their non-conjugated counterparts.
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03:27
Conjugated states
Resonance
Resonance is a concept in organic chemistry where a molecule can be represented by two or more valid Lewis structures, known as resonance structures. The actual structure is a hybrid of these forms, leading to increased stability and reactivity. Compounds with significant resonance stabilization often react more readily due to the distribution of electron density across the molecule.
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03:04Drawing Resonance Structures
Equilibrium Constant
The equilibrium constant (K) is a numerical value that expresses the ratio of the concentrations of products to reactants at equilibrium for a given reaction. A larger K indicates a more favorable reaction, meaning products are favored over reactants. Understanding how structural features, such as conjugation and resonance, influence K is crucial for predicting the reactivity of different compounds.
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02:19The relationship between equilibrium constant and pKa.
Related Practice
Textbook Question
Draw the structure of each compound.
(i) tropylium chloride
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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)
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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)
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Textbook Question
Name the following compounds:
(a)
(b)
(c)
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Textbook Question
One of the following hydrocarbons is much more acidic than the others. Indicate which one, and explain why it is unusually acidic.
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