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Alcohols

Alcohols. Alcohols as Acids. Alcohols as Acids. Alcohols as Acids. Alcohols as Acids resonance in phenols. Methanol and ethanol are industrial chemicals: solvents, antifreeze, fuel, antiseptic, social / recreational Isopropyl alcohol is prepared by hydration of propene.

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Alcohols

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  1. Alcohols

  2. Alcohols as Acids

  3. Alcohols as Acids

  4. Alcohols as Acids

  5. Alcohols as Acids resonance in phenols

  6. Methanol and ethanol are industrial chemicals: solvents, antifreeze, fuel, antiseptic, social / recreational Isopropyl alcohol is prepared by hydration of propene. All alcohols with four carbons or fewer are readily available. Most alcohols with five or six carbons are readily available. Alcohols

  7. Hydration of alkenes Hydroboration-oxidation of alkenes Hydrolysis of alkyl halides Sources of alcohols Reactions discussed in earlier chapters

  8. Reduction of aldehydes and ketones Reduction of carboxylic acids Reduction of esters Reaction of Grignard reagents Sources of alcohols New methods:

  9. Preparation of AlcoholsbyReduction of Aldehydes and Ketones

  10. R R H OH C O C H H Reduction of Aldehydes Gives Primary Alcohols

  11. O + CH3O CH H2 CH3O CH2OH Example: Catalytic Hydrogenation Pt, ethanol (92%)

  12. R H OH C R' Reduction of Ketones Gives Secondary Alcohols R C O R'

  13. O Example: Catalytic Hydrogenation H OH Pt + H2 ethanol (93-95%)

  14. R R C O H OH C H H R R H OH C O C R' R' Retrosynthetic Analysis H:– H:–

  15. act as hydride donors H H – + – + H H Li Na H H Al B H H Metal Hydride Reducing Agents Sodiumborohydride Lithiumaluminum hydride

  16. O2N O2N O CH H OH O Examples: Sodium Borohydride Aldehyde NaBH4 CH2OH methanol (82%) Ketone NaBH4 ethanol (84%)

  17. more reactive than sodium borohydride cannot use water, ethanol, methanol etc.as solvents diethyl ether is most commonly used solvent Lithium aluminum hydride

  18. O CH3(CH2)5CH OH O (C6H5)2CHCHCH3 Examples: Lithium Aluminum Hydride Aldehyde 1. LiAlH4diethyl ether CH3(CH2)5CH2OH 2. H2O (86%) Ketone 1. LiAlH4diethyl ether (C6H5)2CHCCH3 2. H2O (84%)

  19. neither NaBH4 or LiAlH4reduces isolateddouble bonds O H OH Selectivity 1. LiAlH4diethyl ether 2. H2O (90%)

  20. Preparation of Alcohols By Reductionof Carboxylic Acids and Esters

  21. lithium aluminum hydride is only effective reducing agent R H OH C H Reduction of Carboxylic AcidsGives Primary Alcohols R C O HO

  22. O COH CH2OH Example: Reduction of a Carboxylic Acid 1. LiAlH4diethyl ether 2. H2O (78%)

  23. Lithium aluminum hydride preferred forlaboratory reductions Sodium borohydride reduction is too slowto be useful Catalytic hydrogenolysis used in industrybut conditions difficult or dangerous to duplicate in the laboratory (special catalyst, hightemperature, high pressure Reduction of EstersGives Primary Alcohols

  24. O COCH2CH3 1. LiAlH4diethyl ether 2. H2O + CH3CH2OH CH2OH (90%) Example: Reduction of a Carboxylic Acid

  25. Summary

  26. Synthesis of AlcoholsSodium borohydride / Lithium aluminum hydrideReductions

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