Textbook Question
What is the major elimination product obtained from an E2 reaction of each of the following alkyl halides with hydroxide ion?
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Ch. 9 - Substitution and Elimination Reactions of Alkyl Halides
Bruice8th EditionOrganic ChemistryISBN: 9780135213711
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Table of contents
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 1)31
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 2)65
- 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 HalidesProblem 24c,d
Bruice 8th EditionCh. 9 - Substitution and Elimination Reactions of Alkyl HalidesProblem 24c,dChapter 10, Problem 24c,d
Which alkyl halide in each pair is more reactive in an E2 reaction with hydroxide ion?
c. 
d. 
Verified step by step guidance1
Step 1: Understand the E2 reaction mechanism. E2 reactions are bimolecular elimination reactions where a base (such as hydroxide ion) removes a proton from a β-carbon, and a leaving group (such as Br or Cl) departs simultaneously, forming a double bond.
Step 2: Analyze the structure of the alkyl halides. The reactivity in E2 reactions depends on steric hindrance and the ability of the β-hydrogens to be abstracted. Less steric hindrance around the β-hydrogens generally increases reactivity.
Step 3: Compare the first pair of alkyl halides (bromine-containing compounds). The compound on the left has a secondary bromine atom, while the compound on the right has a tertiary bromine atom. Tertiary alkyl halides are more sterically hindered, making it harder for the base to access the β-hydrogens, thus less reactive in E2 reactions.
Step 4: Compare the second pair of alkyl halides (chlorine-containing compounds). The compound on the left has a secondary chlorine atom, while the compound on the right has a tertiary chlorine atom. Similar to the bromine pair, the tertiary alkyl halide is more sterically hindered, reducing its reactivity in E2 reactions.
Step 5: Conclude that in both pairs, the secondary alkyl halides (left structures) are more reactive in E2 reactions with hydroxide ion due to reduced steric hindrance and better accessibility of β-hydrogens.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
E2 Reaction Mechanism
The E2 (bimolecular elimination) reaction is a concerted process where a base removes a proton from a β-carbon while a leaving group departs from the α-carbon, resulting in the formation of a double bond. The reaction rate depends on the concentration of both the alkyl halide and the base, making it a second-order reaction. The steric hindrance and the nature of the leaving group significantly influence the reactivity of the alkyl halide.
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Drawing the E2 Mechanism.
Leaving Group Ability
The ability of a leaving group to depart from the substrate is crucial in determining the reactivity of alkyl halides in E2 reactions. Good leaving groups, such as iodide (I-) and bromide (Br-), stabilize the negative charge better than poorer leaving groups like chloride (Cl-). Therefore, alkyl halides with better leaving groups will generally react more readily in elimination reactions.
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Steric Hindrance
Steric hindrance refers to the crowding around a reactive center in a molecule, which can impede the approach of the base in an E2 reaction. Tertiary alkyl halides are typically more reactive than primary ones due to less steric hindrance, allowing the base to effectively abstract a proton. In the context of the provided pairs, the structure of the alkyl halide influences its reactivity based on steric factors.
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Related Practice
Textbook Question
Which alkyl halide in each pair is more reactive in an E2 reaction with hydroxide ion?
c.
d.
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Textbook Question
Which alkyl halide in each pair is more reactive in an E2 reaction with hydroxide ion?
a.
b.
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Textbook Question
Four alkenes are formed from the E1 reaction of 3-bromo-2,3-dimethylpentane and methanol. Draw the structures of the alkenes and rank them according to the amount that would be formed.
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Textbook Question
What is the major elimination product obtained from an E2 reaction of each of the following alkyl halides with hydroxide ion?
e.
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Textbook Question
Which alkyl halide in each pair is more reactive in an E2 reaction with hydroxide ion?
a.
b.
2
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