Alcohols and Phenols：醇和酚.pptVIP

Protection of Alcohols Hydroxyl groups can easily transfer their proton to a basic reagent This can prevent desired reactions Converting the hydroxyl to a (removable) functional group without an acidic proton protects the alcohol * Methods to Protect Alcohols Reaction with chlorotrimethylsilane in the presence of base yields an unreactive trimethylsilyl (TMS) ether The ether can be cleaved with acid or with fluoride ion to regenerate the alcohol * * Protection-Deprotection * Preparation and Uses of Phenols Industrial process from readily available cumene Forms cumene hydroperoxide with oxygen at high temperature * Laboratory Preparation of Phenols From aromatic sulfonic acids by melting with NaOH at high temperature Limited to the preparation of alkyl-substituted phenols * Reactions of Phenols The hydroxyl group is a strongly activating, making phenols substrates for electrophilic halogenation, nitration, sulfonation, and Friedel–Crafts reactions Reaction of a phenol with strong oxidizing agents yields a quinone Fremys salt [(KSO3)2NO] works under mild conditions through a radical mechanism * * * Mechanism of Reduction The reagent adds the equivalent of hydride to the carbon of C=O and polarizes the group as well Not a complete mechanism!!! * Reduction of Carboxylic Acids and Esters Carboxylic acids and esters are reduced to give primary alcohols LiAlH4 is used because NaBH4 is not effective * Alcohols from Reaction of Carbonyl Compounds with Grignard Reagents Alkyl, aryl, and vinylic halides react with magnesium in ether or tetrahydrofuran to generate Grignard reagents, RMgX Grignard reagents react with carbonyl compounds to yield alcohols * * Mechanism of the Addition of a Grignard Reagent Grignard reagents act as nucleophilic carbon anions (carbanions, : R?) in adding to a carbonyl group The intermediate alkoxide is then protonated to produce the alcohol * Examples of Reactions of Grignard Reagents with Carbonyl Compounds Formaldehyde reacts wit