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Chapter 13 Alcohols, Phenols, and Thiols 13.1 Alcohols, Phenols, and Thiols Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 1 Alcohols and Phenols An alcohol contains A hydroxyl group (—OH) attached to a carbon chain. A phenol contains A hydroxyl group (—OH) attached to a benzene ring. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 2 Classification of Alcohols Alcohols are classified By the number of alkyl groups attached to the carbon bonded to the hydroxyl. As primary (1°), secondary (2°), or tertiary (3°). Primary (1º) 1 group H | CH3—C—OH | H Secondary (2º) Tertiary (3º) 2 groups 3 groups CH3 CH3 | | CH3—C—OH CH3—C—OH | | H CH3 3 Learning Check Classify each alcohol as (P) primary, (S) secondary, or (T) tertiary. OH | 1. CH3—CH—CH2—CH3 2. CH3—CH2—CH2—OH OH | 3. CH3—CH2—C—CH2—CH3 | CH3 4 Solution OH | 1. CH3—CH—CH2—CH3 (S) secondary 2. CH3—CH2—CH2—OH (P) primary OH | 3. CH3—CH2—C—CH2—CH3 | CH3 (T) tertiary 5 Naming Alcohols The names of alcohols In the IUPAC system replace -e of alkane name with ol. that are common names use the name of the alkyl group followed by alcohol. Formula IUPACCommon Name CH4 methane CH3─OH methanol CH3─CH3 ethane CH3─CH2─OH ethanol methyl alcohol ethyl alcohol 6 More Names of Alcohols In IUPAC names for longer carbon chains, the chain is numbered from the end nearest the ─OH group. CH3─CH2─CH2─OH 1-propanol OH │ CH3─CH─CH2─CH3 2-butanol CH3 OH │ │ CH3─CH─CH2─CH2─CH─CH3 5-methyl-2-hexanol 6 5 4 3 2 1 7 Some Typical Alcohols “rubbing alcohol” OH | CH3—CH—CH3 2-propanol (isopropyl alcohol) antifreeze HO—CH2—CH2—OH 1,2-ethanediol (ethylene glycol) glycerol OH | HO—CH2—CH—CH2—OH 1,2,3-propanetriol Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 8 Learning Check Give the IUPAC name for each of the following: 1. CH3—CH2—CH2—CH2—OH 2. OH CH3 | | CH3—CH—CH—CH2—CH3 OH 3. 9 Solution 1. CH3—CH2—CH2—CH2—OH OH CH3 | | 2. CH3—CH—CH—CH2—CH3 3. OH 1-butanol 3-methyl-2-pentanol cyclopentanol 10 Learning Check Write the structure of the following: A. 3-pentanol B. ethyl alcohol C. 3-methylcyclohexanol 11 Solution Write the structure of the following: A. 3-pentanol OH | CH3—CH2—CH—CH2—CH3 CH3 —CH2 —OH B. ethyl alcohol C. 3-methylcyclohexanol OH CH3 12 Naming Phenols To name a phenol with two substituents, Assign C-1 to the carbon attached to the –OH. Number the ring to give the lowest numbers. Use prefixes o, m, and p for common names. OH OH OH Cl Br Phenol 3-chlorophenol (m-chlorophenol) 4-bromophenol (p-bromophenol) 13 Phenols in Medicine Phenol Is the IUPAC name for benzene with a hydroxyl group. Is used in antiseptics and disinfectants. OH OH OH OH OH CH2CH2CH2CH2CH2CH3 phenol resorcinol 4-hexylresorcinol 14 Derivatives of Phenol Compounds of phenol are the active ingredients in the essential oils of cloves, vanilla, nutmeg, and mint. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 15 Learning Check Write the structure of each of the following: A. 3-pentanol B. ethyl alcohol C. p-methylphenol 16 Solution Write the structure of each of the following: A. 3-pentanol OH | CH3—CH2—CH—CH2—CH3 B. ethyl alcohol CH3—CH2—OH OH C. p-methylphenol CH3 17 Thiols Thiols Are carbon compounds that contain a –SH group. Are named in the IUPAC system by adding thiol to the alkane name of the longest carbon chain. 18 Naming Thiols In thiols with long carbon chains, the chain is numbered to locate the –SH group. CH3—CH2—CH2—SH 1-propanethiol SH | CH3—CH—CH3 2-propanethiol 19 Thiols Thiols Often have strong odors. Are used to detect gas leaks. Are found in onions, oysters, and garlic. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 20 Learning Check Draw the structure of each compound. A. 2-butanethiol B. 2-methyl-1-butanol 21 Solution Draw the structure of each compound. A. 2-butanethiol SH | CH3—CH—CH2—CH3 B. 2-methyl-1-butanol CH3 | HO—CH2—CH—CH2—CH3 22 Learning Check Name each of the following compounds: OH | A. CH3—CH2 —CH—CH3 CH3 | B. CH3—CH2—CH—CH2—CH2—OH C. CH3—CH2—CH2—SH 23 Solution Name each of the following compounds: OH | A. CH3—CH2 —CH—CH3 2-butanol CH3 | B. CH3—CH2—CH—CH2—CH2—OH 3-methyl-1-pentanol C. CH3—CH2—CH2—SH 1-propanethiol 24 Chapter 13 Alcohols, Phenols, Ethers, and Thiols 13.2 Ethers Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings 25 Ethers Ethers Contain an ─O─ between two carbon groups. That are simple are named by listing the alkyl names in alphabetical order followed by ether CH3─O─CH3 CH3─CH2─O─CH3 dimethyl ether ethyl methyl ether 26 IUPAC Names for Ethers In the IUPAC system, the shorter alkyl group and the oxygen are named as an alkoxy group attached to the longer alkane. methoxy propane CH3—O—CH2—CH2—CH3 1 2 3 Numbering the longer alkane gives 1-methoxypropane 27 Ethers as Anesthetics Anesthetics Inhibit pain signals to the brain. Such as ethyl ether CH3─CH2─O─CH2─CH3 were used for over a century, but caused nausea and were flammable. Developed by 1960s were nonflammable. Cl F F Cl F H │ │ │ │ │ │ H─C─C─O─C─H H─C─C─O─C─H │ │ │ │ │ │ F F F H F H Ethane(enflurane) Penthrane 28 MTBE Methyl tert-butyl ether CH3 │ CH3─O─C─CH3 │ CH3 Is one of the most produced organic chemicals. Is a fuel additive Is used to improve gasoline combustion. Use is questioned since the discovery that MTBE has contaminated water supplies. 29 Learning Check Draw the structure of each compound. A. diethyl ether B. ethyl methyl ether C. 2-methoxybutane 30 Solution Draw the structure of each compound. A. diethyl ether CH3—CH2—O—CH2—CH3 B. ethyl methyl ether CH3—CH2—O—CH3 C. 2-methoxybutane O—CH3 | CH3—CH—CH2—CH3 31 Cyclic Ethers A cyclic ether Contains an O atom in a carbon ring. Is called a heterocyclic compound. Typically has 5 (furan) or 6 atoms (pyran) in the ring. O O furan O tetrahydrofuran O pyran O 1,4-dioxane 32 Dioxins Dioxins are A group of ethers that are highly toxic. Formed during forest fires and as industrial byproducts. Often carcinogenic. O Cl O Cl Cl CH2 C OH 2,4,5-trichlorophenoxyacetic acid (2,4,5-T; agent orange) Cl O Cl Cl O Cl 2,3,7,8-tetrachlorodibenzodioxin (TTCC, “dioxin”) 33 Learning Check Name each of the following: O 1. 2. CH3 O O 34 Solution 1. 2. O O CH3 methoxy cyclopentane (cyclopentyl methyl ether) 1,4-dioxane O 35 Chapter 13 Alcohols, Phenols, Ethers, and Thiols 13.3 Physical Properties of Alcohols, Phenols, and Ethers Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 36 Boiling Points of Alcohols Alcohols Contain a strongly electronegative O in the OH groups. Form hydrogen bonds between alcohol molecules. Have higher boiling points than alkanes and ethers of similar mass. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 37 Boiling Points of Ethers Ethers Have an O atom, but no H is attached. Cannot form hydrogen bonds between ether molecules. Have boiling points similar to alkanes of similar mass. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 38 Solubility of Alcohols and Ethers in Water Alcohols and ethers are more soluble in water than alkanes because the oxygen atom hydrogen bonds with water. Alcohols with 1-4 C atoms are soluble, but alcohols with 5 or more C atoms are not. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 39 Comparing Solubility and Boiling Points Compound Alkane CH3─CH2─CH3 Molar Boiling Mass Point (°C) 44 -42 Ether CH3─O─CH3 46 -23 Yes 46 78 Yes Alcohol CH3─CH2─OH Soluble in Water? No 40 Solubility of Phenol Phenol Is soluble in water. Has a hydroxyl group that ionizes slightly (weak acid). Is corrosive and irritating to the skin. OH O- + H2O + H3O+ 41 Learning Check Which compound would have the higher boiling point? Explain. ethyl methyl ether or 1-propanol 42 Solution 1-propanol would have the higher boiling point because an alcohol can form hydrogen bonds, but the ether cannot. 43 Learning Check Which compound would be more soluble in water? Explain. ethanol or 2-pentanol 44 Solution Ethanol. An alcohol with two carbons in its carbon chain is more soluble than one with 5 carbons. The longer alkyl chain diminishes the effect of the –OH group. 45 Chapter 13 Alcohols, Phenols, Ethers, and Thiols 13.4 Reactions of Alcohols and Thiols Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 46 Combustion of Alcohols Combustion is the reaction of an alcohol with O2 to produce CO2 and H2O. 2CH3OH + 3O2 2CO2 + 4H2O + Heat Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 47 Dehydration of Alcohols Dehydration of an alcohol occurs When heated with an acid catalyst. With 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 48 Learning Check Write the equations for the reactions when 2-propanol undergoes: 1. combustion 2. dehydration 49 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 50 Formation of Ethers Ethers form when dehydration takes place at low temperature. H+ CH3—OH + HO—CH3 CH3—O—CH3 + H2O two methanol dimethyl ether 51 Oxidation and Reduction In the oxidation of an organic compound There is an increase in the number of C—O bonds. There is a loss of H. In the reduction of an organic compound There is an decrease in the number of C—O bonds. There is a gain of H. 52 Oxidation and Reduction Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 53 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) 54 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] ║ CH3—C—CH3 CH3—C—CH3 + H2O │ H 2-propanol (isopropyl alcohol) 2-propanone(dimethyl ketone, “acetone”) 55 Oxidation of Tertiary (3)Alcohols Tertiary alcohols 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 56 Learning Check Select the compound that would result for each reaction of CH3—CH2—CH2—OH. 1) CH3—CH=CH2 A. H+, heat B. 2) CO2 + H2O O || 3) CH3—CH2—C—H [O] C. O2, heat 57 Solution CH3—CH2—CH2—OH A. H+, heat B. [O] C. O2, heat 1) CH3—CH=CH2 O || 3) CH3—CH2—C—H 2) CO2 + H2O 58 Oxidation of Ethanol in the Body In the body, Ethanol is oxidized by enzymes in the liver. Aldehyde product impairs coordination. O O ║ ║ CH3─CH2─OH CH3─C─H CH3─C─OH ethyl alcohol acetaldehyde acetic acid 2CO2 + H2O 59 Ethanol CH3─CH2─OH 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. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 60 Effect of Alcohol on the Body TABLE 13.2 Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 61 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 62