3 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 + H 2 O | | H H H H alcohol alkene Dehydration of Alcohols
4 Learning Check Write the equations for the reaction of 2-propanol when it undergoes 1. combustion. 2. dehydration.
5 Solution OH │ CH 3 ─CH─CH 3 = 2-propanol = C 3 H 8 O 1. combustion 2C 3 H 8 O + 9O 2 6CO 2 + 8H 2 O 2. dehydration OH │ H + CH 3 ─CH─CH 3 CH 3 ─CH=CH 2 + H 2 O
6 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.
8 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] || CH 3 —C—H CH 3 —C—H + H 2 O | H Ethanol Ethanal (ethyl alcohol) (acetaldehyde) Oxidation of Primary (1 ) Alcohols
9 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 O │ [O] ║ CH 3 ─C─CH 3 CH 3 ─C─CH 3 + H 2 O │ H 2-propanol (isopropyl alcohol) 2-propanol (dimethyl ketone)
10 Oxidation of Tertiary ( 3) Alcohols Tertiary 3 alcohols do not readily oxidize. [O] Tertiary alcoholno reaction OH │ [O] CH 3 ─C─CH 3 no product │ CH 3 no H on the C-OH to oxidize 2-methyl-2-propanol
11 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 ║ ║ CH 3 CH 2 OH CH 3 CH CH 3 COH 2CO 2 + H 2 O ethyl alcohol acetaldehyde acetic acid
12 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. Ethanol CH 3 CH 2 OH