Ch. 11 - Properties and Synthesis of Alkyl Halides: Radical Reactions

Mullins - Organic Chemistry: A Learner Centered Approach 1st Edition

Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471Not the one you use?Change textbook

Mullins 1st Edition

Ch. 11 - Properties and Synthesis of Alkyl Halides: Radical Reactions

Problem 12

Chapter 10, Problem 12

Halohydrin formation is a stereospecific reaction. Identify the products of halohydrin formation of the following diastereomeric alkenes to demonstrate this stereospecificity.

Verified step by step guidance

Step 1: Understand the reaction mechanism for halohydrin formation. Halohydrin formation involves the addition of a halogen (Br2) and water (H2O) across an alkene. The reaction proceeds via a bromonium ion intermediate, followed by nucleophilic attack by water.

Step 2: Analyze the stereochemistry of the starting alkenes. The 'E' alkene has substituents on opposite sides of the double bond, while the 'Z' alkene has substituents on the same side of the double bond. This stereochemistry will influence the orientation of the bromonium ion intermediate.

Step 3: Predict the formation of the bromonium ion intermediate. For the 'E' alkene, the bromonium ion will form with the bromine atom bridging the double bond in a way that minimizes steric hindrance. Similarly, for the 'Z' alkene, the bromonium ion will form with the bromine atom bridging the double bond, but steric interactions will differ due to the substituent positions.

Step 4: Consider the nucleophilic attack by water. Water will attack the more substituted carbon of the bromonium ion, leading to regioselectivity. The stereochemistry of the attack will depend on the orientation of the bromonium ion and the substituents.

Step 5: Identify the final products. The 'E' alkene will yield a halohydrin with anti addition, where the bromine and hydroxyl groups are added to opposite faces of the double bond. The 'Z' alkene will also yield a halohydrin with anti addition, but the stereochemistry of the substituents will differ due to the initial configuration of the alkene.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.

Was this helpful?

Key Concepts

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

Halohydrin Formation

Halohydrin formation is a reaction where an alkene reacts with a halogen (like Br2) in the presence of water, resulting in the addition of a halogen and a hydroxyl group across the double bond. This reaction is stereospecific, meaning that the configuration of the starting alkene influences the stereochemistry of the product, leading to distinct stereoisomers based on the geometry of the alkene.

Stereospecificity

Stereospecificity refers to a reaction where the stereochemistry of the reactant determines the stereochemistry of the product. In the case of halohydrin formation, the E (trans) and Z (cis) isomers of alkenes yield different products due to the specific orientation of the reactants during the reaction, resulting in distinct stereochemical outcomes.

Diastereomers

Diastereomers are stereoisomers that are not mirror images of each other and have different physical properties. In the context of the question, the E and Z alkenes are diastereomers, and their reaction with Br2 and water will produce different halohydrin products, illustrating the concept of stereospecificity in organic reactions.

Recommended video:

Guided course

03:44

Using chiral centers to predict types of stereoisomers.

Related Practice

Textbook Question

Based on the stability of the radicals produced, predict which bond in each pair would have the higher bond-dissociation energy.

(a)

1015

views

Textbook Question

Provide a mechanism for the chlorination of cyclohexane. Be sure to include initiation, propagation, and three possible termination steps.

1432

views

Textbook Question

A radical reaction, as it progressed through its propagation steps, involved the following radical species. Suggest which products might form in all possible termination steps (six products are possible).

889

views

Textbook Question

Predict the product of the following haloalkane syntheses.

(e)

1257

views

Textbook Question

Specify the conditions that would allow the synthesis of the 1° and 3° bromoalkanes from the same starting alkene.

1406

views

Textbook Question

The most stable intermediate forms first. Explain this statement by showing a reaction coordinate diagram for the formation of a 3° carbocation over a 2° carbocation in the following alkene addition reaction.

1008

views