13.4 Reactions of Alcohols and Thiols CH3—CH2—OH(g) + 3O2(g)  2CO2(g) + 3H2O(g) + energy A flaming dessert is prepared using heat from the combustion of an alcohol. Δ Learning Goal Write equations for the combustion, dehydration, and oxidation of alcohols and thiols.

Dehydration of Alcohols Alcohols undergo the loss of — H and — OH from adjacent carbon atoms from the same alcohol, producing an alkene and a water molecule. dehydration when heated with an acid catalyst: H+, heat + H2O alcohol alkene Core Chemistry Skill Writing Equations for the Dehydration of Alcohols

Dehydration of Alcohols The dehydration of a secondary alcohol can result in the formation of a minor product and a major product. Saytzeff’s rule states that the major product is the one that forms by removing the hydrogen from the carbon atom that has the smaller number of hydrogen atoms. hydrogen atoms are easier to remove from the carbon atom adjacent to the carbon atom attached to the — OH group that has fewer hydrogen atoms.

Study Check Draw the condensed structural formula for the major alkene produced by the dehydration of the following alcohol: OH CH3—CH—CH2—CH2—CH3 H+, heat

Solution Draw the condensed structural formula for the major alkene produced by the dehydration of the following alcohol: OH CH3—CH—CH2—CH2—CH3 major product CH3—CH CH—CH2—CH3 H+, heat

Oxidation and Reduction In organic chemistry, oxidation reactions increase the number of carbon–oxygen bonds by the addition of oxygen or a loss of hydrogen atoms. reduction reactions reduce the number of bonds between carbon and oxygen atoms. Core Chemistry Skill Writing Equations for the Oxidation of Alcohols

Oxidation of 1° Alcohols Alcohols undergo oxidation, increasing the number of carbon and oxygen bonds. To indicate the process of oxidation, [O] is placed over the reaction arrow. Primary alcohols are oxidized to produce an aldehyde. 1 bond to O 2 bonds to O [O] 1° alcohol aldehyde

Oxidation of 1° Alcohols Aldehydes can further oxidize to produce a carboxylic acid. 2 bond to O 3 bonds to O [O] aldehyde carboxylic acid

Oxidation of 2° Alcohols Secondary alcohols are oxidized to produce a ketone. 1 bond to O 2 bonds to O [O] 2° alcohol ketone

Oxidation of 3° Alcohols Tertiary alcohols do not readily oxidize because there is no hydrogen atom on the carbon bonded to the — OH group. [O] no product formed no H to oxidize 3° alcohol

Chemistry Link to Health: Methanol Poisoning Methanol is also known as methyl alcohol. highly toxic and found in windshield washer fluid, Sterno, and paint strippers. rapidly absorbed and oxidized to formaldehyde and then formic acid. [O] [O] methyl alcohol formaldehyde formic acid

Oxidation of Thiols When thiols undergo oxidation, an H atom is lost from each of two — SH groups. the product is a disulfide. Protein in hair is cross-linked by disulfide bonds found in the amino acid cysteine. CH3—S—H + H—S—CH3 CH3—S—S—CH3 + H2O [O]

Chemistry Link to Health: Oxidation of Alcohol in the Body Ethanol acts as a depressant and kills or disables more people than does any other drug. consumption can be analyzed by using a breathalyzer. is metabolized by a social drinker at a rate of 12–15 mg/dL per hour. is metabolized by an alcoholic at a rate of 30 mg/dL per hour.

Chemistry Link to Health: Oxidation of Alcohol in the Body The acetaldehyde produced from ethanol in the liver is further oxidized to acetic acid, which is converted to carbon dioxide and water in the citric acid cycle. Liver enzymes can eventually break down ethanol, but the aldehyde and carboxylic acid intermediates can cause considerable damage to liver cells.

Chemistry Link to Health: Oxidation of Alcohol in the Body

Study Check Select the product for the oxidation of [O] A. B. C. CO2 + H2O D.

Solution Select the product for the oxidation of [O] The correct answer is B.

Study Check Select the product when CH3–CH2–CH2–OH undergoes each of the following reactions: [O] [O] A. B. CO2 + H2O D.

Solution Select the product when CH3–CH2–CH2–OH undergoes each of the following reactions: [O] [O] 1. 2. 1. C. 2. D.

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