Summary of ALCOHOLS, PHENOLS AND ETHERS in 47 Minutes || NEET 2024

Summary of the Video: "Alcohols, Phenols AND Ethers in 47 Minutes || NEET 2024"

Main Topics Covered:

• Alcohols: Formation and Reactions
• Phenols: Preparation and Chemical Properties
• Ethers: Synthesis and Reactions
• Important Tests and Reactions for Identification
• Oxidation and Reduction of Alcohols
• Electrophilic Aromatic Substitution in Phenols
• Common Mechanisms and Reaction Pathways
• Practice Questions and Conceptual Clarifications

Detailed Outline:

1. Alcohols: Formation and Reactions

• Acid-Catalyzed Hydration of Alkenes
  - Reaction with H₃O⁺ or diluted H₂SO₄ forms alcohol via carbocation intermediate.
  - Carbocation rearrangement can occur before water addition.
  - Protonation of alkene → carbocation → nucleophilic attack by water → deprotonation → alcohol.
• Hydroboration-Oxidation
  - Anti-Markovnikov addition of water.
  - Reagent: BH₃·THF (borane-tetrahydrofuran complex).
  - Mechanism involves a four-membered cyclic transition state.
  - Syn addition of boron and hydrogen, followed by oxidation with H₂O₂/NaOH to give alcohol.
  - Reaction rate depends on electron-donating groups on alkene.
• Oxymercuration-Demercuration
  - Markovnikov addition of water without rearrangement.
  - Reagents: Hg(OAc)₂ followed by NaBH₄.
  - Anti addition occurs via cyclic mercurinium ion intermediate.
• Reduction of Carbonyl Compounds
  - Aldehydes and ketones reduced by LiAlH₄, NaBH₄, or catalytic hydrogenation (H₂/Pt).
  - Esters reduced only by LiAlH₄, not NaBH₄.
  - Products: primary or secondary Alcohols.
• Grignard Reagents (RMgX)
  - Nucleophilic addition to carbonyls.
  - Forms Alcohols after protonation.
  - Degree of alcohol depends on the alkyl groups attached.
• Acidity of Alcohols
  - Alcohols are acidic due to the ability to lose H⁺ from the hydroxyl group.
  - Acid-base reactions involve protonation and formation of alkoxides.
• Dehydration of Alcohols
  - Heating with concentrated H₂SO₄ leads to alkene formation via E1 mechanism.
  - More stable alkene is the major product.
• Oxidation of Alcohols
  - Primary Alcohols → aldehydes → carboxylic acids (with strong oxidants).
  - Secondary Alcohols → ketones.
  - Tertiary Alcohols generally do not oxidize.
  - Mild oxidants: PCC, PDC, Collins reagent, Cu or Ag at 300°C.
  - Strong oxidants: KMnO₄, K₂Cr₂O₇, HNO₃, Jones reagent.

2. Phenols: Preparation and Chemical Properties

• Preparation of Phenol
  - From chlorobenzene via fusion with molten NaOH at 623 K and 300 atm, followed by acidification.
  - From benzene sulfonic acid by fusion with NaOH and acidification.
  - From cumene hydroperoxide (industrial method) via oxidation and acid treatment, producing phenol and acetone.
• Acidity of Phenol
  - Phenol is more acidic than alcohol due to resonance stabilization of phenoxide ion.
  - Electron-withdrawing groups (e.g., NO₂) increase acidity.
  - Reaction with metals like sodium forms phenoxide salts and releases hydrogen gas.
• Electrophilic Aromatic Substitution (EAS) in Phenols
  - Phenol directs electrophiles to ortho and para positions (due to +M effect).
  - Nitration:
    - Dilute HNO₃ gives ortho and para nitrophenols.
    - Concentrated HNO₃ yields picric acid (2,4,6-trinitrophenol).
  - Halogenation:
    - Bromine water reacts with phenol to give a white precipitate (tribromophenol).
    - Ortho and para substitution occurs; para product is major due to less steric hindrance.
  - Sulfonation:
    - Forms ortho and para sulfonic acids.
  - Reimer-Tiemann Reaction:
    - Phenol reacts with chloroform in basic medium to give salicylaldehyde.

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