Textbook Question
Which of the following compounds show cis-trans isomerism? Draw the cis and trans isomers of the ones that do.
(d)
(e)
(f) CH3CH=NCH3
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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 60
Dimethyl sulfoxide (DMSO) has been used as an anti-inflammatory rub for race horses. DMSO and acetone appear to have similar structures, but the C=O carbon atom in acetone is planar, while the S=O sulfur atom in DMSO is pyramidal. Draw Lewis structures for DMSO and acetone, predict the hybridizations, and explain these observations.
Verified step by step guidance1
Begin by drawing the Lewis structure for acetone. Acetone has the formula \( \text{C}_3\text{H}_6\text{O} \). The central carbon atom is bonded to two methyl groups (\( \text{CH}_3 \)) and an oxygen atom through a double bond. The carbon atom in the \( \text{C}=\text{O} \) bond is sp² hybridized, which results in a planar geometry.
Next, draw the Lewis structure for dimethyl sulfoxide (DMSO). DMSO has the formula \( \text{C}_2\text{H}_6\text{OS} \). The sulfur atom is bonded to two methyl groups (\( \text{CH}_3 \)) and an oxygen atom through a double bond. The sulfur atom in the \( \text{S}=\text{O} \) bond is sp³ hybridized, which results in a pyramidal geometry.
To predict the hybridization of the central atoms, consider the number of electron domains around each atom. In acetone, the carbon atom has three electron domains (two single bonds and one double bond), leading to sp² hybridization. In DMSO, the sulfur atom has four electron domains (two single bonds, one double bond, and one lone pair), leading to sp³ hybridization.
Explain the difference in geometry: The sp² hybridization in acetone results in a trigonal planar geometry around the carbon atom, making the \( \text{C}=\text{O} \) bond planar. In contrast, the sp³ hybridization in DMSO results in a tetrahedral arrangement, but the presence of a lone pair on sulfur leads to a pyramidal shape for the \( \text{S}=\text{O} \) bond.
Summarize the observations: The planar geometry of acetone is due to the sp² hybridization of the carbon atom, while the pyramidal geometry of DMSO is due to the sp³ hybridization of the sulfur atom, influenced by the lone pair of electrons.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Lewis Structures
Lewis structures are diagrams that represent the bonding between atoms in a molecule and the lone pairs of electrons that may exist. They help visualize the arrangement of electrons and the connectivity of atoms, which is crucial for understanding molecular geometry and reactivity. In the case of DMSO and acetone, drawing their Lewis structures reveals the differences in bonding and electron distribution around the central atoms.
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Hybridization
Hybridization is the concept of mixing atomic orbitals to form new hybrid orbitals that can accommodate the bonding requirements of a molecule. In DMSO, the sulfur atom undergoes sp³ hybridization due to its pyramidal geometry, while the carbon atom in acetone is sp² hybridized, resulting in a planar structure. Understanding hybridization is essential for predicting molecular shapes and bond angles.
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Molecular Geometry
Molecular geometry refers to the three-dimensional arrangement of atoms within a molecule, which is influenced by the types of bonds and lone pairs present. The pyramidal shape of DMSO arises from the presence of a lone pair on sulfur, while the planar structure of acetone is due to the absence of lone pairs on the carbon atom. Recognizing these geometrical differences is key to understanding the physical and chemical properties of these compounds.
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Related Practice
Textbook Question
Give the relationships between the following pairs of structures. The possible relationships are as follows: same compound, cis-trans isomers, constitutional (structural) isomers, and not isomers (different molecular formula).
(c)
(d)
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Textbook Question
Give the relationships between the following pairs of structures. The possible relationships are as follows: same compound, cis-trans isomers, constitutional (structural) isomers, and not isomers (different molecular formula).
(a) CH3CH2CH2CH3 and (CH3)3CH
(b) CH2=CH–CH2Cl and CHCl=CH–CH3
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