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Ch. 9 - Substitution and Elimination Reactions of Alkyl Halides
Bruice - Organic Chemistry 8th Edition
Bruice8th EditionOrganic ChemistryISBN: 9780135213711Not the one you use?Change textbook
Chapter 10, Problem 109

Two bromoethers are obtained from the reaction of the following alkyl dihalide with methanol. Draw the structures of the ethers.
Chemical structure of an alkyl dihalide reacting with methanol to form bromoethers.

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1
Analyze the given alkyl dihalide structure: The molecule contains a cyclopentane ring with two chlorine atoms attached to adjacent carbons. One chlorine is on a wedge (indicating it is above the plane), and the other is on a dash (indicating it is below the plane). Additionally, there is a benzyl group attached to the cyclopentane ring.
Understand the reaction conditions: The reaction involves methanol (CH3OH), which acts as a nucleophile. Methanol can substitute the halide groups (chlorine atoms) via an SN2 mechanism, leading to the formation of ethers.
Consider the stereochemistry: Since the reaction proceeds via an SN2 mechanism, the stereochemistry at the carbon centers will invert. This means that the configuration of the carbon bonded to the chlorine will flip when the methanol replaces the chlorine.
Predict the products: Two bromoethers will be formed because the reaction can occur at either of the two carbons bearing chlorine. The first product will have methanol substituting the chlorine on the wedge, while the second product will have methanol substituting the chlorine on the dash. Both products will retain the benzyl group and the cyclopentane ring structure.
Draw the structures of the ethers: For each product, replace one chlorine atom with an OCH3 group (from methanol) while ensuring the stereochemistry is inverted at the substitution site. The remaining chlorine atom stays in its original position.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Nucleophilic Substitution

Nucleophilic substitution is a fundamental reaction in organic chemistry where a nucleophile attacks an electrophile, resulting in the replacement of a leaving group. In this case, methanol acts as the nucleophile, attacking the carbon atom bonded to the halogen in the alkyl dihalide, leading to the formation of bromoethers.
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Nucleophiles and Electrophiles can react in Substitution Reactions.

Ethers

Ethers are organic compounds characterized by an oxygen atom connected to two alkyl or aryl groups. They are formed through the reaction of alcohols with alkyl halides, where the hydroxyl group of the alcohol replaces a halogen atom. Understanding the structure and properties of ethers is crucial for predicting the products of the reaction shown.
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Stereochemistry

Stereochemistry refers to the spatial arrangement of atoms in molecules and how this affects their chemical behavior. In the reaction of the alkyl dihalide with methanol, the stereochemistry of the resulting bromoethers can vary depending on the configuration of the starting material and the mechanism of substitution, which can lead to different isomers.
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Related Practice
Textbook Question

The rate of the reaction of methyl iodide with quinuclidine was measured in nitrobenzene, and then the rate of the reaction of methyl iodide with ­triethylamine was measured in the same solvent. The concentration of the reagents was the same in both experiments.

b. The same experiment was done using isopropyl iodide instead of methyl iodide. Which reaction had the larger rate constant?

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Textbook Question

The rate of the reaction of methyl iodide with quinuclidine was measured in nitrobenzene, and then the rate of the reaction of methyl iodide with ­triethylamine was measured in the same solvent. The concentration of the reagents was the same in both experiments.

c. Which alkyl halide has the larger kquinuclidine/ktriethylamine ratio?

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Textbook Question

Draw the substitution products for each of the following SN2 reactions. If the ­products can exist as stereoisomers, show which stereoisomers are formed:

a. (3S,4S)-3-bromo-4-methylhexane + CH3O-

b. (3S,4R)-3-bromo-4-methylhexane + CH3O-

958
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Textbook Question

The rate of the reaction of methyl iodide with quinuclidine was measured in nitrobenzene, and then the rate of the reaction of methyl iodide with ­triethylamine was measured in the same solvent. The concentration of the reagents was the same in both experiments.

a.Which reaction had the larger rate constant?

696
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Textbook Question

Draw the elimination products for each of the following E2 reactions; if the products can exist as stereoisomers, indicate which stereoisomers are obtained.

a. (2S,3S)-2-chloro-3-methylpentane + high concentration of CH3O

b. (2S,3R)-2-chloro-3-methylpentane + high concentration of CH3O

726
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Textbook Question

Draw the substitution products for each of the following SN2 reactions. If the ­products can exist as stereoisomers, show which stereoisomers are formed:

c. (3R,4R)-3-bromo-4-methylhexane + CH3O-

d. (3R,4S)-3-bromo-4-methylhexane + CH3O-

863
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