Show how you can synthesize the following compounds starting with benzene, toluene, and alcohols containing no more than four carbon atoms as your organic starting materials. Assume that para is the major product (and separable from ortho) in ortho, para mixtures.
(g) 4-isobutylaniline

Verified step by step guidance

1. Step 1: Start with toluene as the base compound. Perform a Friedel-Crafts alkylation using isobutyl chloride (CH3CH(CH3)CH2Cl) and AlCl3 as the catalyst to introduce the isobutyl group at the para position relative to the methyl group. This step gives para-isobutyltoluene as the major product.
2. Step 2: Oxidize the methyl group on the benzene ring of para-isobutyltoluene to a carboxylic acid group. This can be achieved using a strong oxidizing agent such as potassium permanganate (KMnO4) under acidic or basic conditions. The product is para-isobutylbenzoic acid.
3. Step 3: Convert the carboxylic acid group to an amine group (-NH2) through a two-step process. First, reduce the carboxylic acid to a primary amide (-CONH2) using reagents like SOCl2 followed by NH3. Then, reduce the amide to an amine using a reducing agent such as lithium aluminum hydride (LiAlH4). This step yields 4-isobutylaniline.
4. Step 4: Purify the product to isolate 4-isobutylaniline. Since para is the major product, it can be separated from any minor ortho product using techniques like recrystallization or column chromatography.
5. Step 5: Verify the structure of the synthesized compound using spectroscopic techniques such as NMR (nuclear magnetic resonance) and IR (infrared spectroscopy) to confirm the presence of the isobutyl group and the amine group at the para position.

Key Concepts

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. This reaction is crucial for synthesizing substituted aromatic compounds, such as 4-isobutylaniline, from benzene or toluene. Understanding the mechanism of EAS, including the role of activating and deactivating groups, is essential for predicting the outcome of the synthesis.

Nucleophilic Aromatic Substitution (NAS)

Nucleophilic Aromatic Substitution is a reaction where a nucleophile replaces a leaving group on an aromatic compound. This concept is particularly relevant when synthesizing compounds like 4-isobutylaniline, as it may involve the introduction of an amine group onto a substituted aromatic ring. Recognizing the conditions under which NAS occurs, such as the presence of electron-withdrawing groups, is vital for successful synthesis.

Functional Group Interconversion

Functional Group Interconversion refers to the transformation of one functional group into another, which is often necessary in organic synthesis. In the context of synthesizing 4-isobutylaniline, converting alcohols or alkyl groups into amines or other functional groups is essential. Mastery of various reactions, such as reduction or substitution, allows chemists to manipulate starting materials effectively to achieve desired products.