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Ch. 12 - Substitution and Elimination: Reactions of Haloalkanes
Mullins - Organic Chemistry: A Learner Centered Approach 1st Edition
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471Not the one you use?Change textbook
All textbooksMullins 1st EditionCh. 12 - Substitution and Elimination: Reactions of HaloalkanesProblem 56d
Chapter 11, Problem 56d

Predict the product(s) of the following substitution or elimination reactions, paying close attention to the stereochemical outcome of the reactions.
(d)

Verified step by step guidance
1
Identify the type of reaction: The reagent triphenylphosphine (Ph₃P) in tetrahydrofuran (THF) is commonly used in nucleophilic substitution reactions, particularly in the formation of phosphonium salts.
Analyze the substrate: The given substrate is a secondary alkyl bromide. Secondary alkyl halides can undergo nucleophilic substitution reactions, and the bromine atom is a good leaving group.
Determine the mechanism: Triphenylphosphine (Ph₃P) acts as a nucleophile and attacks the carbon atom bonded to the bromine, displacing the bromide ion (Br⁻) in an SN2 mechanism. This results in the formation of a phosphonium salt.
Consider stereochemistry: Since the reaction proceeds via an SN2 mechanism, the configuration at the carbon center will invert. If the starting material has a chiral center, the product will have the opposite stereochemistry.
Write the product: The product will be a phosphonium salt where the triphenylphosphine group (Ph₃P⁺) is bonded to the carbon that originally held the bromine atom, with inversion of configuration if applicable.

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Key Concepts

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

Nucleophilic Substitution Reactions

Nucleophilic substitution reactions involve the replacement of a leaving group in a molecule by a nucleophile. These reactions can occur via two main mechanisms: SN1, which is a two-step process involving carbocation formation, and SN2, which is a one-step process where the nucleophile attacks the substrate simultaneously as the leaving group departs. Understanding the mechanism is crucial for predicting the products and their stereochemistry.
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Elimination Reactions

Elimination reactions involve the removal of a leaving group and a hydrogen atom from adjacent carbon atoms, resulting in the formation of a double bond. The two primary types are E1, which proceeds through a carbocation intermediate, and E2, which is a concerted mechanism. The choice between substitution and elimination often depends on the structure of the substrate and the reaction conditions, influencing the stereochemical outcome.
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Stereochemistry

Stereochemistry refers to the spatial arrangement of atoms in molecules and how this affects their chemical behavior. In substitution and elimination reactions, the stereochemical outcome can lead to different isomers, such as cis/trans or R/S configurations. Understanding stereochemistry is essential for predicting the specific products formed, especially in reactions involving chiral centers or when stereoselectivity is a factor.
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Related Practice
Textbook Question

Predict the major product(s) of the following elimination reactions, paying close attention to the stereochemical outcome of the reactions.

(d)

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Textbook Question

Predict the product(s) of the following substitution or elimination reactions, paying close attention to the stereochemical outcome of the reactions.

(h)

2
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Textbook Question

Predict the major product(s) of the following elimination reactions, paying close attention to the stereochemical outcome of the reactions.

(f)

2
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Textbook Question

Predict the product(s) of the following substitution or elimination reactions, paying close attention to the stereochemical outcome of the reactions.

(e)

1
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Textbook Question

Predict the product(s) of the following substitution or elimination reactions, paying close attention to the stereochemical outcome of the reactions.

(a)

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Textbook Question

Predict the product(s) of the following substitution or elimination reactions, paying close attention to the stereochemical outcome of the reactions.

(g)

2
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