Ch. 15 - Conjugated Systems, Orbital Symmetry, and Ultraviolet Spectroscopy

Wade9th EditionOrganic ChemistryISBN: 9780135213728Not the one you use?Change textbook

Wade 9th Edition

Ch. 15 - Conjugated Systems, Orbital Symmetry, and Ultraviolet Spectroscopy

Problem 25a

Chapter 15, Problem 25a

Predict the products of the following reactions.
(a) allyl bromide + cyclohexyl magnesium bromide

Verified step by step guidance

Identify the type of reaction: This reaction involves an organometallic reagent (cyclohexyl magnesium bromide, a Grignard reagent) and an alkyl halide (allyl bromide). Grignard reagents typically act as nucleophiles in reactions with electrophiles.

Analyze the reactivity of the Grignard reagent: The cyclohexyl magnesium bromide contains a cyclohexyl group bonded to magnesium. The carbon attached to magnesium is highly nucleophilic due to the polar carbon-magnesium bond.

Determine the electrophilic site in allyl bromide: In allyl bromide, the carbon bonded to the bromine atom is electrophilic because bromine is more electronegative and withdraws electron density from the carbon.

Predict the nucleophilic attack: The nucleophilic cyclohexyl group from the Grignard reagent will attack the electrophilic carbon of allyl bromide, displacing the bromide ion (Br⁻) as a leaving group. This results in the formation of a new carbon-carbon bond.

Write the product structure: The product will be an alkane where the cyclohexyl group is bonded to the allyl group (CH₂=CH-CH₂). The bromide ion (Br⁻) is a byproduct of the reaction.

Verified video answer for a similar problem:

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

Video duration:

Was this helpful?

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 the case of allyl bromide, the bromine atom acts as a leaving group, allowing the nucleophile (cyclohexyl magnesium bromide) to form a new bond with the carbon atom that was previously bonded to bromine.

Grignard Reagents

Grignard reagents are organomagnesium compounds that act as strong nucleophiles in organic reactions. Cyclohexyl magnesium bromide is a Grignard reagent that can react with electrophiles, such as allyl bromide, to form new carbon-carbon bonds. This reaction is crucial for building complex organic molecules and is a key tool in synthetic organic chemistry.

Reaction Mechanism

Understanding the reaction mechanism is essential for predicting the products of organic reactions. In this case, the mechanism involves the nucleophilic attack of the Grignard reagent on the allyl bromide, leading to the formation of a new carbon-carbon bond. Analyzing the mechanism helps in anticipating the structure of the final product and understanding the steps involved in the reaction.

Recommended video:

Guided course

02:16

Heck Reaction Mechanism

Related Practice

Textbook Question

Match four of the following UV absorption maxima (λ_max) with the corresponding compounds: (1) 232 nm; (2) 256 nm; (3) 273 nm; (4) 292 nm; (5) 313 nm; (6) 353 nm.

1796

views

Textbook Question

Predict the products of the following reactions.

(b) cyclopentadiene + anhydrous HCl

1777

views

Textbook Question

Predict the products of the following reactions.

2388

views

Textbook Question

Phenolphthalein is an acid–base indicator that is colorless below pH 8 and red above pH 8. Explain briefly why the first structure is colorless and the second structure is colored.

1009

views

Textbook Question

Predict the products of the following reactions.

(d) furan + trans-1,2-dicyanoethylene

Classify the following dienes and polyenes as isolated, conjugated, cumulated, or some combination of these classifications.

(a) cycloocta-1,4-diene

(b) cycloocta-1,3-diene