Untitled Quiz

Halogenation of Benzene and Phenol

• Halogenation of benzene requires a Lewis acid (e.g., FeBr3) to polarize the halogen molecule.
• Phenol can induce polarization of bromine without a Lewis acid due to the activating –OH group.
• Bromination of phenol with bromine water yields 2,4,6-tribromophenol as a white precipitate.

Reactions of 3-Methylphenol

• Mononitration: Occurs at the position influenced by –OH and –CH3 groups.
• Dinitration: More complex as both groups influence the product distribution.
• Mononitration of Phenyl Methanoate: Positioning of incoming groups affected by functional groups.

Kolbe’s Reaction

• Treating phenol with sodium hydroxide generates a phenoxide ion, which is more reactive towards electrophiles.
• The phenoxide reacts with carbon dioxide, yielding ortho hydroxybenzoic acid (salicylic acid) as the main product.

Reimer-Tiemann Reaction

• Treating phenol with chloroform in sodium hydroxide introduces a –CHO group at the ortho position.
• Benzal chloride is an intermediate that hydrolyzes to salicylaldehyde.

Reaction with Zinc Dust

• Phenol reacts with zinc dust under heat to convert into benzene.

Oxidation of Phenol

• Oxidation with chromic acid produces benzoquinone, a conjugated diketone.
• Phenols oxidize slowly in air to form dark mixtures containing quinones.

Commercially Important Alcohols

• Methanol (CH3OH): Known as ‘wood spirit’, produced mainly by catalytic hydrogenation of carbon monoxide; toxic and colorless.
• Production Methods: Methanol can also be produced from the reduction of carboxylic acids and esters using lithium aluminium hydride (LiAlH4) for special chemicals.

Grignard Reagent Reactions

• Grignard reagents react with aldehydes and ketones to produce alcohols.
• Methanal gives primary alcohols, other aldehydes yield secondary alcohols, and ketones produce tertiary alcohols upon hydrolysis.

Important Notes

• Reagent quantities indicate sequential reactions.
• LiAlH4 is a strong but costly reducing agent used for specialized applications.
• Understanding the orientation of electrophilic substitution is crucial for predicting products from nitration and electrophilic reactions in aromatic compounds.