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Lecture 4 Alcohols, Phenols, and Thiols Alcohols, Phenols, and Thiols Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 1 Midterm II Outcome 30% 25% % Student 20% 15% 10% 5% 0% > 90 80-90 70-79 50-70 < 50 Score on Test Class Average: 75 High Score: 103 Low Score: 32 2 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 3 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 4 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 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 Learning Check Write the structure of the following: A. 3-pentanol B. ethyl alcohol C. 3-methylcyclohexanol 10 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) 11 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 12 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 13 Learning Check Write the structure of each of the following: A. 3-pentanol B. ethyl alcohol C. p-methylphenol 14 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. 15 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 16 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 17 Learning Check Draw the structure of each compound. A. 2-butanethiol B. 2-methyl-1-butanol 18 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 19 Pause: Group Activity Do the following problems on ALE 4 Problem # 1, parts A to F Problem # 2, parts A to D 20 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 21 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 22 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 23 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. 24 Learning Check Draw the structure of each compound. A. diethyl ether B. ethyl methyl ether C. 2-methoxybutane 25 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 26 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”) 27 Learning Check Name each of the following: O 1. 2. CH3 O O 28 Pause: Group Activity Do the following problems on ALE 4 Problem # 1, parts G to I Problem # 2, parts E to F 29 Lecture 4 13.3 Physical Properties of Alcohols, Phenols, and Ethers Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 30 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 31 Boiling Points of Ethers Ethers Have an O atom, but no H is attached. Cannot form hydrogen bonds between ether molecules. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 32 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 33 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 34 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+ 35 Learning Check Which compound would have the higher boiling point? Explain. ethyl methyl ether or 1-propanol 36 Learning Check Which compound would be more soluble in water? Explain. ethanol or 2-pentanol 37 Pause: Group Activity Do the following problems on ALE 4 Problem # 3 Problem # 4 38 Lecture 4 13.4 Reactions of Alcohols and Thiols Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 39 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 40 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 41 Learning Check Write the equations for the reactions when 2-propanol undergoes: 1. combustion 2. dehydration 42 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 43 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. 44 Oxidation and Reduction Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 45 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) 46 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”) 47 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 48 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 49 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 50 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 51 Effect of Alcohol on the Body TABLE 13.2 Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 52 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 53 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 54 Pause: Group Activity Do the following problems on ALE 4 Problem # 5 55