Electrophilic Aromatic Substitution, Kolbe Video Lecture | Chemistry for JEE Main & Advanced

Ans. Electrophilic aromatic substitution is a reaction where an electrophile replaces a hydrogen atom on an aromatic ring. It occurs due to the high electron density in the aromatic ring, making it susceptible to attack by electrophiles.

Ans. The steps involved in electrophilic aromatic substitution are as follows: 1. Generation of the electrophile: An electrophile is formed by the reaction of a strong Lewis acid with a reagent. 2. Attack of the electrophile: The electrophile attacks the aromatic ring, breaking the aromaticity and forming a sigma complex. 3. Rearrangement or elimination: Depending on the reaction conditions, the sigma complex can undergo rearrangement or elimination to restore the aromaticity. 4. Regeneration of the catalyst: The catalyst used in the generation of the electrophile is regenerated in the final step of the reaction.

Ans. The Kolbe reaction is a type of electrophilic aromatic substitution reaction that involves the decarboxylation of a carboxylic acid in the presence of a strong base. It leads to the formation of an aromatic hydrocarbon. The reaction proceeds through the formation of a carboxylate anion, which then undergoes electrophilic substitution to replace a hydrogen atom on the aromatic ring.

Ans. The key factors that influence electrophilic aromatic substitution reactions are: 1. Nature of the electrophile: The reactivity and selectivity of the reaction depend on the nature of the electrophile. Electron-withdrawing groups increase reactivity, while electron-donating groups decrease it. 2. Nature of the aromatic ring: The electron density and substitution pattern on the aromatic ring affect the reactivity and regioselectivity of the reaction. 3. Reaction conditions: Reaction temperature, solvent, and presence of catalysts or additives can significantly influence the reaction outcome. 4. Steric hindrance: Bulky substituents on the aromatic ring can hinder the attack of the electrophile, leading to steric effects. 5. Resonance effects: The presence of electron-donating or electron-withdrawing groups on the aromatic ring can influence the electron density and reactivity of the ring.

Ans. Some common examples of electrophilic aromatic substitution reactions include: 1. Nitration: Introduction of a nitro group (NO2) onto the aromatic ring. 2. Halogenation: Introduction of a halogen atom (F, Cl, Br, I) onto the aromatic ring. 3. Friedel-Crafts alkylation: Introduction of an alkyl group onto the aromatic ring using an alkyl halide and a Lewis acid catalyst. 4. Friedel-Crafts acylation: Introduction of an acyl group onto the aromatic ring using an acyl chloride and a Lewis acid catalyst. 5. Sulfonation: Introduction of a sulfonic acid group (SO3H) onto the aromatic ring.