Textbook Question
Determine whether the following pairs of structures are actually different compounds or simply resonance forms of the same compounds.
a.
b.
c.
d.
2
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Ch.1 - Structure and Bonding
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 1, Problem 42j,k
Draw the important resonance forms to show the delocalization of charges in the following ions. In each case, indicate the major resonance form(s).
(j) 
(k) 
Verified step by step guidance1
Identify the conjugated system in each ion. For ion j, [CH3CH=CHCH=CHCH2CH2]+, the conjugated system involves the alternating single and double bonds starting from the second carbon. For ion k, [CH2CH=CHOCH=CH2]+, the conjugated system involves the alternating single and double bonds starting from the first carbon.
For ion j, draw the initial structure with the positive charge on the terminal carbon (CH2). Then, move the pi electrons from the double bond between the second and third carbon to form a new double bond between the first and second carbon, shifting the positive charge to the third carbon.
Continue the resonance for ion j by moving the pi electrons from the double bond between the fourth and fifth carbon to form a new double bond between the third and fourth carbon, shifting the positive charge to the fifth carbon. Repeat this process to explore all possible resonance structures.
For ion k, start with the initial structure where the positive charge is on the oxygen atom. Move the pi electrons from the double bond between the first and second carbon to form a new double bond between the oxygen and the second carbon, shifting the positive charge to the first carbon.
Continue the resonance for ion k by moving the pi electrons from the double bond between the fourth and fifth carbon to form a new double bond between the third and fourth carbon, shifting the positive charge to the fifth carbon. Explore all possible resonance structures and identify the major resonance form based on the stability of the structures (e.g., full octets, charge distribution).
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Resonance Structures
Resonance structures are different Lewis structures for a molecule that depict the same arrangement of atoms but differ in the distribution of electrons. They are used to represent delocalized electrons within certain molecules or polyatomic ions where the bonding cannot be expressed by a single Lewis structure. The true structure is a hybrid of all possible resonance forms.
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Delocalization of Charges
Delocalization of charges refers to the distribution of electron density across multiple atoms, which can stabilize ions or molecules. In resonance, this involves the movement of electrons, typically pi electrons or lone pairs, across adjacent atoms, reducing the energy of the system. This concept is crucial for understanding the stability and reactivity of organic ions.
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Major and Minor Resonance Forms
In resonance, not all structures contribute equally to the resonance hybrid. Major resonance forms are those that are more stable, typically having full octets on atoms, minimal formal charges, and negative charges on more electronegative atoms. Minor forms are less stable and contribute less to the overall hybrid. Identifying these helps predict the most likely structure and properties of the ion.
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Related Practice
Textbook Question
Determine whether the following pairs of structures are actually different compounds or simply resonance forms of the same compounds.
e.
f.
g.
h.
3
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Textbook Question
In the following sets of resonance forms, label the major and minor contributors and state which structures would be of equal energy. Add any missing important resonance forms.
(d)
(e)
1
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Textbook Question
For each of these ions, draw the important resonance forms and predict which resonance form is likely to be the major contributor.
(a)
2
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Textbook Question
Determine whether the following pairs of structures are actually different compounds or simply resonance forms of the same compounds.
i.
j.
k.
l.
2
views
Textbook Question
For each of these ions, draw the important resonance forms and predict which resonance form is likely to be the major contributor.
(b)
3
views