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Questions and Answers
What major product is formed when phenol is treated with bromine water?
Which group in phenol enhances the reactivity towards electrophilic substitution?
What is the main product formed from Kolbe’s reaction using phenol?
In the Reimer-Tiemann reaction, what functional group is introduced to the ortho position of the benzene ring?
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What reaction occurs when phenoxide ions react with carbon dioxide?
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What is the primary method of commercial production of methanol?
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What is the major product of acid-catalyzed dehydration of butan-1-ol?
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Which reaction generates a phenolic product through the Reimer-Tiemann reaction?
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Which of the following correctly represents a resonance structure of phenoxide ion derived from ortho or para nitrophenol?
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What is the primary reaction occurring in Kolbe’s reaction?
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Study Notes
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.
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