Synthesize from benzene. (Hint: All of these require diazonium ions.)
(d) 4-methoxyaniline

Verified step by step guidance

1. Step 1: Start with benzene as the base compound. Perform a nitration reaction by treating benzene with a mixture of concentrated HNO₃ (nitric acid) and concentrated H₂SO₄ (sulfuric acid). This introduces a nitro group (-NO₂) onto the benzene ring, forming nitrobenzene.
2. Step 2: Reduce the nitro group (-NO₂) in nitrobenzene to an amino group (-NH₂) to form aniline. This can be achieved using a reducing agent such as Sn (tin) and HCl, or Fe (iron) and HCl, followed by neutralization with a base.
3. Step 3: Convert the amino group (-NH₂) in aniline to a diazonium ion (-N₂⁺) by performing a diazotization reaction. Treat aniline with NaNO₂ (sodium nitrite) and HCl at 0–5°C to form the diazonium salt (benzene diazonium chloride).
4. Step 4: Replace the diazonium group (-N₂⁺) with a methoxy group (-OCH₃) to form 4-methoxyaniline. This can be achieved through a Sandmeyer reaction using Cu₂O and methanol (CH₃OH) as the reagents. The methoxy group will be introduced at the para position relative to the amino group.
5. Step 5: Ensure the product is purified and characterized to confirm the synthesis of 4-methoxyaniline. Techniques such as recrystallization, melting point determination, and spectroscopic analysis (e.g., IR, NMR) can be used for verification.

Key Concepts

Benzene and its Derivatives

Benzene is a fundamental aromatic hydrocarbon characterized by its stable ring structure and delocalized π-electrons. Understanding benzene's reactivity is crucial, as it undergoes electrophilic substitution reactions rather than addition, allowing for the introduction of various functional groups while preserving its aromaticity.

Diazonium Ions

Diazonium ions are highly reactive intermediates formed from primary aromatic amines and nitrous acid. They play a pivotal role in organic synthesis, particularly in the formation of azo compounds and in electrophilic aromatic substitution reactions, where they can introduce substituents onto aromatic rings.

Electrophilic Aromatic Substitution

Electrophilic aromatic substitution (EAS) is a key reaction mechanism in organic chemistry where an electrophile replaces a hydrogen atom on an aromatic ring. This process is essential for synthesizing substituted aromatic compounds, such as 4-methoxyaniline, by utilizing diazonium ions to introduce new functional groups onto the benzene ring.