Chapter15-4 - Chapter 15 Alcohols, Diols, and Thiols O H...

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Chem 212 B. R. Kaafarani 1 Chapter 15 Alcohols, Diols, and Thiols O H O H
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Chem 212 B. R. Kaafarani 2 15.1. Sources of Alcohols Methanol Methanol is an industrial chemical. - End uses: solvent, antifreeze, fuel. - Principal use: preparation of formaldehyde. - Prepared by hydrogenation of carbon monoxide. CO + 2H 2 CH 3 OH
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Chem 212 B. R. Kaafarani 3 Ethanol is an industrial chemical. Most ethanol comes from fermentation. Synthetic ethanol is produced by hydration of ethylene. Synthetic ethanol is denatured (made unfit for drinking) by adding methanol, benzene, pyridine, castor oil, gasoline, etc. Ethanol
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Chem 212 B. R. Kaafarani 4 Other Alcohols Isopropyl alcohol is prepared by hydration of propene. Isopropyl alcohol evaporates quickly from the skin (bp. 82 o C) and has a cooling effect. It is used as rubbing alcohol and to sterilize medical instruments. Most alcohols with five or six carbons are readily available.
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Chem 212 B. R. Kaafarani 5 Hydration of alkenes. Hydroboration-oxidation of alkenes. Hydrolysis of alkyl halides. Syntheses using: - Grignard reagents. - Organolithium reagents. Reactions discussed in earlier chapters (Table 15.1) Sources of alcohols
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Chem 212 B. R. Kaafarani 6 - Reduction of aldehydes and ketones. - Reduction of carboxylic acids. - Reduction of esters. - Reaction of Grignard reagents with epoxides. - Diols by hydroxylation of alkenes. New methods in Chapter 15 Sources of alcohols
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Chem 212 B. R. Kaafarani 7 C R HO H H C R H O Reduction of Aldehydes Gives Primary Alcohols 15.2. Preparation of Alcohols by Reduction of Aldehydes and Ketones
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Chem 212 B. R. Kaafarani 8 Pt, ethanol (92%) CH 3 OC H 2 OH O CH 3 H + H 2 Example: Catalytic Hydrogenation Pt, Pd, Ni, or Ru as effective catalysts.
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Chem 212 B. R. Kaafarani 9 C R HO H R' C R R' O Reduction of Ketones Gives Secondary Alcohols (93-95%) + H 2 O Pt ethanol H Example: Catalytic Hydrogenation
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Chem 212 B. R. Kaafarani 10 “H : –” “H : –” C R H O H H C R H O C R H O H R' C R R' O Retrosynthetic Analysis
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Chem 212 B. R. Kaafarani 11 Sodium borohydride Lithium aluminum hydride Li + Na + B H H H H Al H H H H act as hydride donors Metal Hydride Reducing Agents
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Chem 212 B. R. Kaafarani 12 NaBH 4 (82%) CH 2 OH O CH O 2 N methanol O 2 N O HO H (84%) NaBH 4 ethanol Aldehyde Ketone Examples: Sodium Borohydride
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Chem 212 B. R. Kaafarani 13 Lithium Aluminum Hydride More reactive than sodium borohydride. Cannot use water, ethanol, methanol etc. as solvents. Diethyl ether is most commonly used solvent.
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Chem 212 B. R. Kaafarani 14 (84%) Aldehyde Ketone O CH 3 (CH 2 ) 5 CH CH 3 (CH 2 ) 5 CH 2 OH 1. LiAlH 4 , diethyl ether 2. H 2 O O (C 6 H 5 ) 2 CHCCH 3 1. LiAlH 4 , diethyl ether 2. H 2 O (86%) OH (C 6 H 5 ) 2 CHCHCH 3 Examples: Lithium Aluminum Hydride
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Chem 212 B. R. Kaafarani 15 HO H O 1. LiAlH 4 , diethyl ether 2. H 2 O (90%) Selectivity Neither NaBH 4 or LiAlH 4 reduces isolated double bonds.
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Chem 212 B. R. Kaafarani 16 Lithium aluminum hydride is the only effective reducing agent.
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This note was uploaded on 01/06/2012 for the course CHEM 212 taught by Professor Bilalkaafarani during the Fall '10 term at American University of Beirut.

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Chapter15-4 - Chapter 15 Alcohols, Diols, and Thiols O H...

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