Draw the product(s) of each of the following reactions: a. benzoic acid + HNO3/H2SO4 b. isopropylbenzene + Cl2 + FeCl3

Ch. 18 - Reactions of Benzene and Substituted Benzenes

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Bruice 8th Edition

Ch. 18 - Reactions of Benzene and Substituted Benzenes

Problem 48a,b

Chapter 19, Problem 48a,b

Draw the product(s) of each of the following reactions:
a. benzoic acid + HNO₃/H₂SO₄
b. isopropylbenzene + Cl₂ + FeCl₃

Verified step by step guidance

Step 1: Analyze the reaction conditions for part (a). The reagents HNO3 (nitric acid) and H2SO4 (sulfuric acid) indicate a nitration reaction, which is an electrophilic aromatic substitution. Benzoic acid is the substrate, and the nitro group (-NO2) will be introduced onto the benzene ring.

Step 2: Determine the directing effects of the substituent on benzoic acid. The carboxylic acid group (-COOH) is an electron-withdrawing group and a meta-director. This means the nitro group will preferentially substitute at the meta position relative to the -COOH group.

Step 3: Draw the product for part (a). The benzene ring of benzoic acid will have a nitro group (-NO2) added at the meta position relative to the carboxylic acid group.

Step 4: Analyze the reaction conditions for part (b). The reagents Cl2 and FeCl3 indicate a chlorination reaction, which is another example of electrophilic aromatic substitution. Isopropylbenzene (cumene) is the substrate, and a chlorine atom will be introduced onto the benzene ring.

Step 5: Determine the directing effects of the substituent on isopropylbenzene. The isopropyl group (-CH(CH3)2) is an electron-donating group and an ortho/para-director. This means the chlorine atom will preferentially substitute at the ortho or para positions relative to the isopropyl group. Draw the product with chlorine added at one of these positions.

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Key Concepts

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

Electrophilic Aromatic Substitution (EAS)

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 the question, benzoic acid reacts with a mixture of nitric acid and sulfuric acid, generating a nitronium ion (NO2+) that acts as the electrophile, leading to nitration of the aromatic ring.

Nitration of Benzoic Acid

The nitration of benzoic acid involves the introduction of a nitro group (-NO2) into the aromatic ring. The position of substitution is influenced by the electron-withdrawing carboxylic acid group, which directs the electrophile to the meta position relative to itself, resulting in the formation of meta-nitrobenzoic acid as a product.

Free Radical Halogenation

Free radical halogenation is a reaction where alkanes or aromatic compounds react with halogens in the presence of a catalyst to form haloalkanes or haloaromatic compounds. In the case of isopropylbenzene (cumene) reacting with chlorine in the presence of FeCl3, the reaction proceeds via a free radical mechanism, leading to the formation of chlorinated products, typically at the benzylic position.