Textbook Question
Show how each of the following compounds can be synthesized from benzene:
f. m-xylene
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19. Reactions of Aromatics: EAS and Beyond
EAS:Retrosynthesis
7:24 minutesProblem 52f
Textbook Question
Show how the following compounds can be synthesized from benzene:
f. m-hydroxybenzoic acid
Verified step by step guidance1
Step 1: Begin with benzene as the starting material. Perform a nitration reaction by treating benzene with a mixture of concentrated HNO₃ and H₂SO₄. This introduces a nitro group (-NO₂) onto the benzene ring, forming nitrobenzene.
Step 2: Reduce the nitro group (-NO₂) in nitrobenzene to an amino group (-NH₂) using a reducing agent such as Sn/HCl or Fe/HCl. This forms aniline.
Step 3: Protect the amino group (-NH₂) by acetylation. React aniline with acetic anhydride to form acetanilide. This step prevents unwanted reactions during subsequent steps.
Step 4: Perform a Friedel-Crafts acylation reaction on acetanilide using CO₂ and AlCl₃ to introduce a carboxylic acid group (-COOH) in the meta position relative to the protected amino group. This forms m-acetylaminobenzoic acid.
Step 5: Hydrolyze the acetanilide group under acidic or basic conditions to remove the acetyl group and regenerate the amino group. Then oxidize the amino group to a hydroxyl group (-OH) using a suitable oxidizing agent, such as NaNO₂/HCl, to yield m-hydroxybenzoic acid.
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7mKey Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Electrophilic Aromatic Substitution
Electrophilic aromatic substitution (EAS) is a fundamental reaction in organic chemistry where an electrophile replaces a hydrogen atom on an aromatic ring. This process is crucial for synthesizing substituted aromatic compounds, such as m-hydroxybenzoic acid from benzene. Understanding the mechanism of EAS, including the role of the electrophile and the stability of the carbocation intermediate, is essential for predicting the products of reactions involving benzene derivatives.
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Ortho/Para vs. Meta Directing Groups
In electrophilic aromatic substitution, substituents on the benzene ring can influence the position of further substitutions. Ortho and para directing groups favor substitution at the 2 and 4 positions, while meta directing groups lead to substitution at the 3 position. Recognizing the directing effects of functional groups, such as hydroxyl (-OH) and carboxylic acid (-COOH), is vital for determining the correct synthesis pathway for m-hydroxybenzoic acid.
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Functional Group Transformations
Functional group transformations involve converting one functional group into another through various chemical reactions. In the synthesis of m-hydroxybenzoic acid, the transformation of a nitrile (-CN) group into a carboxylic acid (-COOH) is a key step. Familiarity with common reactions, such as hydrolysis of nitriles, is necessary to understand how to achieve the desired functional groups in the final product.
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