Domanda del libro di testo
What substitution products are obtained when each of the following compounds is added to a solution of sodium acetate in acetic acid?
a. 2-chloro-2-methyl-3-hexene
b. 3-bromo-1-methylcyclohexene
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Ch. 9 - Substitution and Elimination Reactions of Alkyl Halides
Bruice8th EditionOrganic ChemistryISBN: 9780135213711
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TOC.tableOfContents
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding31
- Ch. 2 - Acids and Bases: Central to Understanding Organic Chemistry84
- Ch. 3 - An Introduction to Organic Compounds: Nomenclature, Physical Properties, and Structure183
- Ch. 4 - Isomers: The Arrangement of Atoms in Space121
- Ch. 5 - Alkenes: Structure, Nomenclature, and an Introduction to Reactivity • Thermodynamics and Kinetics83
- Ch. 6 - The Reactions of Alkenes • The Stereochemistry of Addition Reactions175
- Ch. 7 - The Reactions of Alkynes • An Introduction to Multistep Synthesis119
- Ch. 8 - Delocalized Electrons: Their Effect on Stability, pKa, and the Products of a Reaction • Aromaticity and Electronic Effects: An Introduction to the Reactions of Benzene148
- Ch. 9 - Substitution and Elimination Reactions of Alkyl Halides212
- Ch. 10 - Reactions of Alcohols, Ethers, Epoxides, Amines, and Sulfur-Containing Compounds131
- Ch. 11 - Organometallic Compounds60
- Ch. 12 - Radicals90
- Ch. 13 - Mass Spectrometry; Infrared Spectroscopy; UV/Vis Spectroscopy62
- Ch. 14 - NMR Spectroscopy95
- Ch. 15 - Reactions of Carboxylic Acids and Carboxylic Acid Derivatives123
- Ch. 16 - Reactions of Aldehydes and Ketones • More Reactions of Carboxylic Acid Derivatives141
- Ch. 17 - Reactions at the Alpha-Carbon101
- Ch. 18 - Reactions of Benzene and Substituted Benzenes144
- Ch. 19 - More About Amines • Reactions of Heterocyclic Compounds49
- Ch. 20 - The Organic Chemistry of Carbohydrates80
- Ch. 21 - Amino Acids, Peptides, and Proteins57
- Ch. 22 - Catalysis in Organic Reactions and in Enzymatic Reactions35
- Ch. 23 - The Organic Chemistry of the Coenzymes—Compounds Derived from Vitamins1
- Ch. 28 - Pericyclic Reactions58
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Bruice 8th EditionCh. 9 - Substitution and Elimination Reactions of Alkyl HalidesProblema 102
Bruice 8th EditionCh. 9 - Substitution and Elimination Reactions of Alkyl HalidesProblema 102Capitolo 9, Problema 102
cis-1-Bromo-4-tert-butylcyclohexane and trans-1-bromo-4-tert-butylcyclohexane both react with sodium ethoxide in ethanol to form 4-tert-butylcyclohexene. Explain why the cis isomer reacts much more rapidly than the trans isomer.
Guida verificata passo dopo passo1
Analyze the structure of cis-1-bromo-4-tert-butylcyclohexane and trans-1-bromo-4-tert-butylcyclohexane. In both cases, the cyclohexane ring adopts a chair conformation, and the bulky tert-butyl group will preferentially occupy the equatorial position to minimize steric strain.
In the cis isomer, the bromine atom is in the axial position when the tert-butyl group is equatorial. This arrangement allows for a favorable anti-periplanar geometry between the β-hydrogen (on the adjacent carbon) and the leaving group (bromine), which is a requirement for the E2 elimination mechanism.
In the trans isomer, the bromine atom is in the equatorial position when the tert-butyl group is equatorial. This arrangement does not provide the necessary anti-periplanar geometry between the β-hydrogen and the leaving group, making the E2 elimination less favorable.
The anti-periplanar geometry is critical for the E2 mechanism because it allows for the proper orbital alignment for the base (sodium ethoxide) to abstract the β-hydrogen and for the leaving group (bromine) to depart simultaneously, forming the double bond.
As a result, the cis isomer reacts much more rapidly than the trans isomer because the anti-periplanar geometry is readily available in the cis isomer, facilitating the elimination reaction to form 4-tert-butylcyclohexene.
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Steric Hindrance
Steric hindrance refers to the repulsion between atoms that occurs when they are brought close together, which can affect the reactivity of molecules. In the case of cis-1-bromo-4-tert-butylcyclohexane, the bulky tert-butyl group is positioned on the same side as the bromine atom, allowing for a more favorable transition state during the reaction. In contrast, the trans isomer has the tert-butyl group on the opposite side, leading to increased steric hindrance and a less favorable reaction pathway.
Video consigliato:
02:53
Understanding steric effects.
E2 Elimination Mechanism
The E2 elimination mechanism involves the simultaneous removal of a leaving group and a hydrogen atom from adjacent carbon atoms, resulting in the formation of a double bond. For the cis isomer, the spatial arrangement allows for the necessary anti-periplanar orientation of the leaving bromine and the hydrogen atom, facilitating a faster reaction. The trans isomer, however, may not achieve this optimal orientation as easily, leading to a slower reaction rate.
Video consigliato:
09:36Drawing the E2 Mechanism.
Conformational Analysis
Conformational analysis studies the different spatial arrangements of a molecule that can occur due to rotation around single bonds. In cyclohexane derivatives, the chair conformation is the most stable, but the positioning of substituents can significantly influence reactivity. The cis isomer can adopt a conformation that minimizes steric strain and maximizes the accessibility of the bromine for elimination, while the trans isomer may have a less favorable conformation, contributing to its slower reaction rate.
Video consigliato:
03:29Understanding what a conformer is.
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