Question

Show how you would convert aniline to the following compounds. (c) 1,3,5-trimethylbenzene

Accepted Answer

Step 1: Begin with aniline (C₆H₅NH₂) as the starting material. The amino group (-NH₂) is an activating group and ortho/para-directing in electrophilic aromatic substitution reactions. However, for this transformation, the amino group must first be removed to allow for the introduction of methyl groups in a symmetrical 1,3,5 arrangement. Step 2: Protect the amino group by converting it into an acetamide group. This can be achieved by reacting aniline with acetic anhydride (CH₃CO₂O) to form acetanilide (C₆H₅NHCOCH₃). This step reduces the reactivity of the amino group and prevents unwanted side reactions. Step 3: Perform a nitration reaction on acetanilide to introduce nitro groups (-NO₂) at the meta positions relative to the acetamide group. Use a mixture of concentrated HNO₃ and H₂SO₄ to achieve this. The product will be 1,3,5-trinitrobenzene. Step 4: Reduce the nitro groups to amine groups (-NH₂) using a reducing agent such as tin (Sn) and hydrochloric acid (HCl). This will yield 1,3,5-triaminobenzene. Step 5: Perform a diazotization reaction on 1,3,5-triaminobenzene by treating it with sodium nitrite (NaNO₂) and HCl at 0°C to form diazonium salts. Then, replace the diazonium groups with methyl groups (-CH₃) using a Sandmeyer reaction with methyl iodide (CH₃I) and a copper catalyst. This will yield 1,3,5-trimethylbenzene as the final product.

Show how you would convert aniline to the following compounds.
(c) 1,3,5-trimethylbenzene

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Key Concepts

Aniline Structure and Reactivity

Electrophilic Aromatic Substitution (EAS)

Friedel-Crafts Alkylation