Textbook Question
a. Draw the structure of cis-CH3CH=CHCH2CH3 showing the pi bond with its proper geometry.
b. Circle the six coplanar atoms in this compound.
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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 57
In pent-2-yne (CH3CCCH2CH3), there are four atoms in a straight line. Use dashed lines and wedges to draw a three-dimensional representation of this molecule, and circle the four atoms that are in a straight line.
Verified step by step guidance1
Identify the structure of pent-2-yne: The molecule is an alkyne, which means it contains a carbon-carbon triple bond. The structure is CH3-C≡C-CH2-CH3.
Determine the geometry around the triple bond: The carbon atoms involved in the triple bond (C≡C) are linear, meaning they form a straight line with a bond angle of 180 degrees.
Draw the three-dimensional structure: Start by drawing the linear portion of the molecule, which includes the carbon atoms involved in the triple bond and the adjacent carbon atoms. Use dashed lines and wedges to represent the spatial orientation of the remaining bonds. Dashed lines indicate bonds going away from the viewer, while wedges indicate bonds coming towards the viewer.
Circle the atoms in a straight line: In the structure of pent-2-yne, the four atoms in a straight line are the two carbon atoms involved in the triple bond and the two adjacent carbon atoms. Circle these atoms to highlight their linear arrangement.
Review the representation: Ensure that the three-dimensional drawing accurately reflects the linear geometry of the alkyne portion and that the spatial orientation of the other bonds is correctly depicted using dashed lines and wedges.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Molecular Geometry
Molecular geometry refers to the three-dimensional arrangement of atoms within a molecule. In organic chemistry, understanding the spatial orientation of atoms is crucial for visualizing molecular structures. For alkynes like pent-2-yne, the linear geometry around the triple bond is a key feature, as it dictates the alignment of atoms in a straight line.
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Molecular Geometry Explained.
Alkyne Structure
Alkynes are hydrocarbons characterized by a carbon-carbon triple bond, which imparts a linear geometry to the bonded carbon atoms. In pent-2-yne, the triple bond between the second and third carbon atoms results in a linear arrangement of these carbons and the adjacent hydrogen atoms, forming a straight line in the molecule.
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Dash and Wedge Notation
Dash and wedge notation is a method used to depict three-dimensional molecular structures on a two-dimensional plane. Solid wedges represent bonds coming out of the plane towards the viewer, while dashed lines indicate bonds going behind the plane. This notation helps visualize the spatial arrangement of atoms, essential for identifying linear alignments in molecules like pent-2-yne.
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Related Practice
Textbook Question
Circle the coplanar atoms in the following structure:
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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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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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Textbook Question
Which of the following compounds show cis-trans isomerism? Draw the cis and trans isomers of the ones that do.
(a) CH3CH=CHCH3
(b) CH3C≡CCH3
(c) CH2=C(CH3)2
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Textbook Question
Draw orbital pictures of the pi bonding in the following compounds:
f. CH3CH=NCH=C=O
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