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.
Category
Educational
