Textbook Question
Draw complete Lewis structures for the following condensed structural formulas.
(d) CH2CHCHO
(e) (CH3)3CCOCHCH2
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 10c
Use resonance structures to identify the areas of high and low electron density in the following compounds:
(c) 
Verified step by step guidance1
Identify the functional groups in the molecule. The given compound is an amide, specifically formamide, with a carbonyl group (C=O) and an amine group (NH2) attached to the same carbon.
Draw the Lewis structure of the molecule to visualize the distribution of electrons. The carbonyl group has a double bond between carbon and oxygen, and the amine group has a lone pair on the nitrogen.
Consider the resonance structures. In formamide, resonance can occur between the lone pair on the nitrogen and the carbonyl group. This involves the movement of electrons from the nitrogen to form a double bond with the carbon, while the double bond between carbon and oxygen shifts to give oxygen a negative charge.
Analyze the resonance structures to determine areas of high and low electron density. The oxygen in the carbonyl group, due to its electronegativity and resonance, will have a partial negative charge, indicating high electron density. The carbonyl carbon, being electron-deficient, will have a partial positive charge, indicating low electron density.
Conclude that the nitrogen atom, due to its lone pair and involvement in resonance, can also have areas of high electron density, especially when considering the resonance structure where it forms a double bond with carbon.
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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 help in understanding the delocalization of electrons within a molecule, which can affect the molecule's stability, reactivity, and electron density distribution. In the given compound, resonance can occur between the carbonyl group and the adjacent nitrogen atom.
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Electron Density
Electron density refers to the probability of finding electrons in a particular region of a molecule. Areas of high electron density are typically associated with lone pairs or π-bonds, while areas of low electron density are often found around atoms with partial positive charges. In the compound shown, the carbonyl oxygen is likely to have high electron density due to its electronegativity and lone pairs.
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Carbonyl Group
The carbonyl group (C=O) is a functional group characterized by a carbon atom double-bonded to an oxygen atom. It is highly polar due to the difference in electronegativity between carbon and oxygen, leading to a partial positive charge on carbon and a partial negative charge on oxygen. This polarity influences the electron density distribution and reactivity of the molecule, making the carbonyl carbon an electrophilic center.
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Related Practice
Textbook Question
For each of the following compounds, draw the important resonance forms. Indicate which structures are major and minor contributors or whether they have the same energy.
(g)
(h)
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Textbook Question
Give Lewis structures corresponding to the following line–angle structures. Give the molecular formula for each structure.
(a)
(b)
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Textbook Question
Use resonance structures to identify the areas of high and low electron density in the following compounds:
(d)
2
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Textbook Question
For each of the following compounds, draw the important resonance forms. Indicate which structures are major and minor contributors or whether they have the same energy.
(e) [CH3C(OH)2]+
(f) [CH2CHNH]–
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Textbook Question
Draw the important resonance forms of the following cations and anions:
(c)
(d)
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