Textbook Question
Draw and name all stereoisomers of 3-chlorohepta-2,4-diene
b. using the E-Z nomenclature.
Ch. 7 - Structure and Synthesis of Alkenes; Elimination
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 7, Problem 46b
For each alkene, indicate the direction of the dipole moment. For each pair, determine which compound has the larger dipole moment
b. cis-1,2-dibromoethene or trans-2,3-dibromobut-2-ene
Verified step by step guidance1
Identify the molecular structure of each compound: cis-1,2-dibromoethene and trans-2,3-dibromobut-2-ene. Draw their structures to visualize the arrangement of atoms and substituents.
Understand the concept of dipole moment: It is a vector quantity that depends on the difference in electronegativity between atoms and the distance between them. In alkenes, the dipole moment is influenced by the substituents attached to the double bond.
For cis-1,2-dibromoethene, note that both bromine atoms are on the same side of the double bond, which can lead to a net dipole moment due to the additive effect of the individual dipoles from each C-Br bond.
For trans-2,3-dibromobut-2-ene, observe that the bromine atoms are on opposite sides of the double bond, which can cause the dipoles to cancel each other out, resulting in a smaller net dipole moment.
Compare the net dipole moments: The cis isomer typically has a larger dipole moment than the trans isomer due to the alignment of dipoles in the same direction, leading to a greater overall dipole moment in the cis compound.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Dipole Moment
The dipole moment is a measure of the separation of positive and negative charges in a molecule. It is a vector quantity, having both magnitude and direction, and is influenced by the electronegativity of atoms and the geometry of the molecule. In alkenes, the dipole moment is affected by the presence and orientation of substituents around the double bond.
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How dipole-dipole forces work.
Cis-Trans Isomerism
Cis-trans isomerism is a type of stereoisomerism where the relative orientation of functional groups within a molecule differs. In 'cis' isomers, similar groups are on the same side of the double bond, while in 'trans' isomers, they are on opposite sides. This orientation affects the molecule's physical properties, including its dipole moment, due to differences in spatial arrangement.
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Electronegativity and Bond Polarity
Electronegativity is the tendency of an atom to attract electrons in a bond. When two atoms with different electronegativities form a bond, the electrons are not shared equally, resulting in bond polarity. In alkenes, the presence of electronegative atoms like bromine can create polar bonds, contributing to the overall dipole moment of the molecule.
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Related Practice
Textbook Question
A double bond in a six-membered ring is usually more stable in an endocyclic position than in an exocyclic position. Hydrogenation data on two pairs of compounds follow. One pair suggests that the energy difference between endocyclic and exocyclic double bonds is about 9 kJ/mol. The other pair suggests an energy difference of about 5 kJ/mol. Which number do you trust as being more representative of the actual energy difference? Explain your answer.
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Textbook Question
Draw and name all stereoisomers of 3-chlorohepta-2,4-diene
a. using the cis-trans nomenclature.
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Textbook Question
For each alkene, indicate the direction of the dipole moment. For each pair, determine which compound has the larger dipole moment.
c. cis-1,2-dibromo-1,2-dichloroethene or cis-1,2-dichloroethene
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Textbook Question
For each alkene, indicate the direction of the dipole moment. For each pair, determine which compound has the larger dipole moment.
a. cis-1,2-difluoroethene or trans-1,2-difluoroethene
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Textbook Question
The energy difference between cis- and trans-but-2-ene is about 4 kJ/mol; however, the trans isomer of 4,4-dimethylpent-2-ene is nearly 16 kJ/mol more stable than the cis isomer. Explain this large difference.
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