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Chapter 13 Organic Compounds with Oxygen and Sulfur 13.3 Reactions of Alcohols and Thiols Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings 1 Combustion of Alcohols Alcohols undergo combustion with O2 to produce CO2 and H2O. 2CH3OH + 3O2 2CO2 + 4H2O + Heat Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings 2 Dehydration of Alcohols Alcohols undergo • dehydration when heated with an acid catalyst. • the loss of —H and —OH from adjacent carbon atoms. H OH | | H+, heat H—C—C—H H—C=C—H + H2O | | | | H H H H alcohol alkene 3 Learning Check Write the equations for the reaction of 2-propanol when it undergoes 1. combustion. 2. dehydration. 4 Solution OH │ CH3─CH─CH3 = 2-propanol = C3H8O 1. combustion 2C3H8O + 9O2 2. dehydration OH │ CH3─CH─CH3 6CO2 + 8H2O H+ CH3─CH=CH2 + H2O 5 Oxidation and Reduction In an oxidation, • there is an increase in the number of C-O bonds. • there is a loss of H. In a reduction, • there is an decrease in the number of C-O bonds. • there is a gain of H. 6 Oxidation and Reduction 7 Oxidation of Primary (1) Alcohols When a primary alcohol is oxidized, [O], • one H is removed from the –OH. • another H is removed from the carbon bonded to the OH. • an aldehyde is produced. [O] Primary alcohol Aldehyde OH O | [O] || CH3—C—H CH3—C—H + H2O | H Ethanol (ethyl alcohol) Ethanal (acetaldehyde) 8 Oxidation of Secondary (2) Alcohols When a secondary alcohol is oxidized, [O], • one H is removed from the –OH. • another H is removed from the carbon bonded to the OH. • a ketone is produced. [O] secondary alcohol ketone OH │ CH3─C─CH3 │ H O ║ CH3─C─CH3 + H2O [O] 2-propanol (isopropyl alcohol) 2-propanol (dimethyl ketone) 9 Oxidation of Tertiary ( 3)Alcohols Tertiary 3alcohols do not readily oxidize. [O] Tertiary alcohol no reaction OH │ [O] CH3─C─CH3 no product │ CH3 no H on the C-OH to oxidize 2-methyl-2-propanol 10 Oxidation of Ethanol in the Body In the body, • enzymes in the liver oxidize ethanol. • aldehyde product impairs coordination. • blood alcohol over 0.4% can be fatal. O O ║ ║ CH3CH2OH CH3CH CH3COH ethyl alcohol acetaldehyde 2CO2 + H2O acetic acid 11 Ethanol CH3CH2OH Ethanol • acts as a depressant. • kills or disables more people than any other drug. • is metabolized at a rate of 12-15 mg/dL per hour by a social drinker. • is metabolized at a rate of 30 mg/dL per hour by an alcoholic. 12 Effect of Alcohol on the Body 13 Alcohol Contents in Common Products % Ethanol 50% 40% 15-25% 12% 3-9% Product Whiskey, rum, brandy Flavoring extracts Listerine, Nyquil, Scope Wine, Dristan, Cepacol Beer, Lavoris 14 Oxidation of Thiols When thiols undergo oxidation, • an H atom is lost from each of two –SH groups. • the product is a disulfide. [O] CH3─SH + HS─CH3 CH3─S─S─CH3 + H2O 15 Learning Check Select the product for the oxidation of OH │ [O] CH3─CH─CH2─CH3 1) CH3─CH=CH─CH3 3) CO2 + H2O O ║ 2) CH3─C─CH2 ─CH3 OH │ 4) CH3─CH─CH2─CH3 16 Solution Select the product for the oxidation of OH │ [O] CH3─CH─CH2─CH3 O ║ 2) CH3─C─CH2 ─CH3 17 Learning Check Select the product when CH3—CH2—CH2—OH undergoes each of the following reactions: A) H+, heat B) [O] C) + O2 1) CH3—CH=CH2 2) CO2 + H2O O || 3) CH3—CH2—C—H 18 Solution B. 1) CH3—CH=CH2 O || 3) CH3—CH2—C—H C. + O2 2) CO2 + H2O A. H+, heat [O] 19