Chapter 20: Problem 43

Treatment of anthranilic acid with nitrous acid gives an intermediate, \(\mathbf{A}\), that contains a diazonium ion and a carboxylate group. When this intermediate is heated in the presence of furan, a bicyclic compound is formed. Propose a structural formula for compound \(\mathrm{A}\) and a mechanism for the formation of the bicyclic product.

Short Answer

Expert verified

Answer: The structure of intermediate A can be represented as a benzene ring with a diazonium ion (N2+) connected to one carbon atom and a carboxylate group (-COO-) connected to the adjacent carbon atom. The mechanism for the formation of the bicyclic compound involves the following steps: (1) nucleophilic attack of furan oxygen on the diazonium carbon, (2) loss of nitrogen gas, (3) rearrangement and proton transfer, and (4) deprotonation, resulting in a bicyclic product involving the benzene ring and the furan ring connected through two bridging carbons.

Step by step solution

Determine the structure of anthranilic acid

Anthranilic acid is an aromatic compound with the molecular formula \(\displaystyle C_{7} H_{7} NO_{2}\). Its structure can be represented as a benzene ring with an amine group (-NH2) connected to one carbon atom and a carboxylic acid group (-COOH) connected to the adjacent carbon atom.

Determine the structure of intermediate A

When anthranilic acid reacts with nitrous acid (HNO2), the amine group (-NH2) of anthranilic acid is converted to a diazonium ion (-N2+). We also know that intermediate A contains a carboxylate group (-COO-), which forms from the deprotonation of the carboxylic acid group. Thus, the structure of intermediate A can be represented as a benzene ring with a diazonium ion (N2+) connected to one carbon atom and a carboxylate group (-COO-) connected to the adjacent carbon atom.

Propose a mechanism for the formation of the bicyclic compound

Upon heating in the presence of furan, intermediate A undergoes a reaction with the furan ring. The mechanism proceeds as follows: 1. Nucleophilic attack: The furan oxygen atom with a lone pair of electrons acts as a nucleophile and attacks the electrophilic diazonium carbon of intermediate A. This results in the formation of a new C-O bond between furan and the intermediate. 2. Loss of nitrogen gas: The nitrogen-nitrogen bond in the diazonium group breaks, resulting in the loss of nitrogen gas (N2) and the formation of a carbocation at the previous diazonium carbon. 3. Rearrangement and proton transfer: The carbocation can rearrange by migrating the carboxylate group (-COO-) to the adjacent carbon, forming a new C-O bond. This results in a bicyclic compound with one positive charge in its structure. 4. Deprotonation: Finally, a base (likely the solvent or furan) can deprotonate the positively charged carbon, resulting in the neutral bicyclic product. This proposed mechanism should result in a bicyclic product involving the benzene ring and the furan ring connected through two bridging carbons.

Unlock Step-by-Step Solutions & Ace Your Exams!

Full Textbook Solutions
Get detailed explanations and key concepts
Unlimited Al creation
Al flashcards, explanations, exams and more...
Ads-free access
To over 500 millions flashcards
Money-back guarantee
We refund you if you fail your exam.

Start your free trial

Over 30 million students worldwide already upgrade their learning with Vaia!

Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Diazonium Ion Formation

The process of transforming an amine group into a diazonium ion is an intriguing and pivotal reaction in organic chemistry. This transformation typically involves amine compounds reacting with nitrous acid (HNO2), a reaction that's especially important when applied to an aromatic amine like anthranilic acid. When anthranilic acid's amine group reacts with nitrous acid, it leads to the formation of a diazonium ion, denoted by –N2+. This reactive ion incorporates a nitrogen double bond where the positive charge is stabilized over the two nitrogen atoms.

Diazonium ions are central to numerous synthetic applications due to their ability to be substituted with a variety of different functional groups. In this case, the diazonium ion is integral to the subsequent formation of the bicyclic compound through a reaction with furan. The synthesis processes through the diazonium ion are often exothermic and require careful control of temperature to ensure correct product formation and avoid decomposition or undesirable side reactions.

Synthesis of Bicyclic Compounds

The synthesis of bicyclic compounds is a fascinating area within organic chemistry, and it highlights the complex ways in which molecular frameworks can be constructed. Bicyclic compounds consist of two ring structures that are atomically interconnected. In the context of the exercise, the formation of a bicyclic compound occurs when intermediate A, containing the diazonium group, reacts with furan.

The reaction yields a compound where the benzene ring of anthranilic acid and the furan ring are bridged together - a transformation that implicates several key steps including nucleophilic attack, loss of nitrogen gas, and rearrangement which is followed by proton transfer. The key to the successful synthesis of a bicyclic compound often hinges on the stability of the intermediate and the correct positioning of reactive sites on the molecular scaffold, allowing the rings to form the bicyclic structure seamlessly.

Nucleophilic Attack in Organic Chemistry

A nucleophilic attack is a cornerstone reaction mechanism in organic chemistry, where a nucleophile, an electron-rich species, targets an electron-deficient site, known as an electrophile. In this example, the furan’s oxygen with lone electrons acts as the nucleophile. It attacks the positively charged carbon atom in the diazonium ion of intermediate A, which is the electrophile, thereby forming a new carbon-oxygen (C-O) bond.

This type of reaction is central to forming the structural complexity seen in organic compounds. Nucleophilic attacks are responsible for creating new bonds, thereby significantly altering the structure, and often the function, of the resultant molecule. Understanding the propensities of various nucleophiles and electrophiles, as well as the conditions under which they react, is crucial for predicting and controlling the outcomes of these reactions.

Recommended explanations on Chemistry Textbooks

View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Short Answer

Step by step solution

Determine the structure of anthranilic acid

Determine the structure of intermediate A

Propose a mechanism for the formation of the bicyclic compound

Key Concepts

Diazonium Ion Formation

Synthesis of Bicyclic Compounds

Nucleophilic Attack in Organic Chemistry

One App. One Place for Learning.

Most popular questions from this chapter

Recommended explanations on Chemistry Textbooks

Organic Chemistry

Kinetics

Inorganic Chemistry

Chemical Analysis

Making Measurements

Ionic and Molecular Compounds

Study anywhere. Anytime. Across all devices.