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Ch. 16 - Aromatic Compounds
Wade - Organic Chemistry 9th Edition
Wade9th EditionOrganic ChemistryISBN: 9780135213728Not the one you use?Change textbook
Chapter 16, Problem 14

When 3-chlorocyclopropene is treated with AgBF4, AgCl precipitates. The organic product can be obtained as a crystalline material, soluble in polar solvents such as nitromethane but insoluble in hexane. When the crystalline material is dissolved in nitromethane containing KCl, the original 3-chlorocyclopropene is regenerated. Determine the structure of the crystalline material, and write equations for its formation and its reaction with chloride ion.

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1
Step 1: Analyze the reaction of 3-chlorocyclopropene with AgBF4. The Ag+ ion reacts with the Cl- ion from 3-chlorocyclopropene to form AgCl as a precipitate. This indicates that the Cl- ion is removed from the cyclopropene ring, leaving behind a positively charged cyclopropene cation.
Step 2: Consider the structure of the organic product. The removal of Cl- from 3-chlorocyclopropene results in the formation of a cyclopropene cation. This cation is stabilized by resonance and can interact with BF4- to form a crystalline salt, [cyclopropene]+[BF4]-.
Step 3: Write the equation for the formation of the crystalline material. The reaction can be represented as: CH(2)(3)Cl+Ag(BF4)CH(2)(3)+Ag(Cl)
Step 4: Analyze the reaction of the crystalline material with KCl in nitromethane. The cyclopropene cation reacts with Cl- from KCl to regenerate 3-chlorocyclopropene. This demonstrates the reversible nature of the reaction.
Step 5: Write the equation for the regeneration of 3-chlorocyclopropene. The reaction can be represented as: CH(2)(3)+K(Cl)CH(2)(3)+K(BF4)

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Key Concepts

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

Electrophilic Aromatic Substitution

Electrophilic aromatic substitution is a fundamental reaction in organic chemistry where an electrophile replaces a hydrogen atom on an aromatic ring. In the context of 3-chlorocyclopropene, the presence of the chlorine atom makes the compound more reactive towards electrophiles, facilitating the formation of a new product when treated with AgBF4. Understanding this mechanism is crucial for predicting the structure of the resulting crystalline material.

Solubility Principles

Solubility principles dictate that 'like dissolves like,' meaning polar substances tend to dissolve in polar solvents, while nonpolar substances dissolve in nonpolar solvents. The crystalline material's solubility in nitromethane (a polar solvent) but not in hexane (a nonpolar solvent) suggests that it possesses polar functional groups or characteristics, which is essential for determining its structure and behavior in reactions.

Nucleophilic Substitution Reactions

Nucleophilic substitution reactions involve the replacement of a leaving group (like Cl) by a nucleophile (such as KCl in this case). The regeneration of 3-chlorocyclopropene from the crystalline material upon treatment with KCl indicates that the crystalline product likely contains a reactive site that can undergo nucleophilic attack, leading to the reformation of the original compound. This concept is vital for writing the reaction equations and understanding the transformation processes involved.