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 58a,b,c
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
Verified step by step guidance1
Step 1: Understand the concept of cis-trans isomerism. Cis-trans isomerism occurs in compounds with restricted rotation around a double bond, where two substituents can be positioned on the same side (cis) or opposite sides (trans) of the double bond. For cis-trans isomerism to occur, the double-bonded carbon atoms must each have two different groups attached.
Step 2: Analyze compound (a) CH3CH=CHCH3. This compound has a double bond between the second and third carbon atoms. Each of these carbons has two different groups attached: one has a CH3 group and a hydrogen atom, and the other has a CH3 group and a hydrogen atom. Therefore, this compound can exhibit cis-trans isomerism.
Step 3: Analyze compound (b) CH3C≡CCH3. This compound has a triple bond between the second and third carbon atoms. Triple bonds do not allow for cis-trans isomerism because the linear geometry of the triple bond does not permit the spatial arrangement required for cis-trans isomerism. Thus, this compound does not exhibit cis-trans isomerism.
Step 4: Analyze compound (c) CH2=C(CH3)2. This compound has a double bond between the first and second carbon atoms. However, the second carbon atom is attached to two identical CH3 groups, which means there are not two different groups attached to the double-bonded carbons. Therefore, this compound does not exhibit cis-trans isomerism.
Step 5: Draw the cis and trans isomers for compound (a). In the cis isomer, the CH3 groups are on the same side of the double bond, while in the trans isomer, the CH3 groups are on opposite sides of the double bond. Use proper chemical drawing conventions to represent these isomers.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Cis-Trans Isomerism
Cis-trans isomerism, also known as geometric isomerism, occurs in alkenes and cyclic compounds where the arrangement of substituents around a double bond or ring structure can differ. In cis isomers, similar groups are on the same side, while in trans isomers, they are on opposite sides. This difference in spatial arrangement can significantly affect the physical and chemical properties of the compounds.
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Alkenes and Double Bonds
Alkenes are hydrocarbons that contain at least one carbon-carbon double bond (C=C). The presence of this double bond restricts rotation, allowing for the possibility of cis-trans isomerism. Understanding the structure and reactivity of alkenes is crucial for identifying which compounds can exhibit geometric isomerism.
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Criteria for Isomerism
For a compound to exhibit cis-trans isomerism, it must have restricted rotation around a double bond and must possess two different substituents on each carbon of the double bond. This means that if a compound has identical groups on both sides of the double bond, it cannot form cis-trans isomers. Recognizing these criteria is essential for determining which compounds in the question can show isomerism.
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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).
(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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Textbook Question
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.
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