Chapter Fourteen Alcohols, Phenols, And Ethers Functional Groups • Groups of atoms within a larger molecule that have characteristic chemical behavior. • A functional group behaves almost the _____ way in every molecule it is in (electronic structure, reactivity, geometry all generally stay the ______). • The chemistry of every organic molecule is determined by the functional groups it contains. • It is very important for this course that you learn to recognize functional groups. Ch 14 | 2 of 52 Functional Groups Name Alkane (Not a functional Group) Structure C Alkene Alkyne Arene (aromatic ring) H3C C C H2C C C Example C CH3 CH2 HC CH H C C C C C C C HC CH HC CH C H Ch 14 | 3 of 52 Functional Groups Name Structure Halide C Alcohol C X Example H3C OH H3C C H3C Cl OH Ether C O O CH3 Ch 14 | 4 of 52 Alcohols, Phenols, and Ethers cont’d Fig. 14.1 Space-filling models for the three simplest unbranched chain alcohols: methyl alcohol, ethyl alcohol, and propyl alcohol. Ch 14 | 5 of 52 The Bonding of Oxygen • To understand the bonding patterns of oxygen, we must review what we know about oxygen – How many valence electrons does oxygen have? – How many electrons does oxygen need to have an octet of electrons in its valence shell? – Oxygen’s octet is filled when it forms ___ bonds to other atoms: Ch 14 | 6 of 52 Alcohols, Phenols, and Ethers cont’d → Fig. 14.2 The similar shapes of water and methanol. Methyl alcohol may be viewed structurally as an alkyl derivative of water. Ch 14 | 7 of 52 Classifying Alcohols • Alcohols are classified by the number of carbon substituents bonded to the carbon. – primary (1o) – secondary (2o) – tertiary (3o) R C H Primary R H H OH R C OH R Secondary R C OH R Tertiary Ch 14 | 8 of 52 Alcohols, Phenols, and Ethers cont’d Which are primary? Which are secondary? Which are tertiary? Ch 14 | 9 of 52 Alcohols Used As Fuels and Fuel Additives ← Fig. 14.3 Racing cars are fueled with methyl alcohol. Jonathan Ferrey/Getty Images Ch 14 | 10 of 52 Ethyl Alcohol In Beverages and Other Consumer Products Ch 14 | 11 of 52 Commercial Uses of Alcohols ← Fig. 14.5 Ethylene glycol is the major ingredient in deicers for planes. © Hank Morgan/Rainbow Ch 14 | 12 of 52 Metabolic Alcohols → Fig. 14.6 For survival in northern winters, many fish and insects produce large amount of glycerol that dissolve in their blood, thereby lowering the freezing point. James Cotier/Getty Images Ch 14 | 13 of 52 Naming Alcohols A carbon compound that contain -OH (hydroxyl) group In IUPAC name, the -e in alkane name is replaced with -ol. CH4 methane CH3OH CH3CH3 methanol (methyl alcohol) ethane CH3CH2OH ethanol (ethyl alcohol) Ch 14 | 14 of 52 Naming Alcohols, Part II IUPAC names for longer chains number the chain from the end nearest the -OH group. CH3CH2CH2OH 1-propanol OH CH3CHCH3 CH3 2-propanol OH CH3CHCH2CH2CHCH3 5-methyl-2-hexanol Ch 14 | 15 of 52 Some Typical Alcohols OH “rubbing alcohol” CH3CHCH3 2-propanol (isopropyl alcohol) antifreeze HO-CH2-CH2-OH 1,2-ethanediol (ethylene glycol) OH glycerol HO-CH2-CH-CH2OH Ch 14 | 16 of 52 Name these alcohols. OH HO OH OH OH OH Ch 14 | 17 of 52 Alcohols, Phenols, and Ethers cont’d Fig. 14.7 (a) The polar hydroxyl functional group dominates the physical properties of methanol. (b) Conversely, the nonpolar portion of 1octanol dominates its physical properties. Ch 14 | 18 of 52 Alcohols, Phenols, and Ethers cont’d ← Fig. 14.8 (a) Boiling points and (b) solubilities in water of selected 1alcohols. Ch 14 | 19 of 52 Alcohols, Phenols, and Ethers cont’d Table 14.3 Ch 14 | 20 of 52 Alcohols, Phenols, and Ethers cont’d ← Fig. 14.10 Alcohol boiling points are higher than those of the corresponding alkanes because of the alcohol-alcohol hydrogen bonding. Ch 14 | 21 of 52 Alcohols, Phenols, and Ethers cont’d → Fig. 14.11 Because of hydrogen bonding between alcohol molecules and water molecules, small molecular mass alcohols have unlimited solubility in water. Ch 14 | 22 of 52 Synthesis of Alcohols • Alcohols can be prepared from many other kinds of compounds. • Hydration! R-X Alkyl halides Ketones Aldehydes Esters R-C-R =O – – – – R=R =O – Alkenes R-OH alcohol R-C-H R-O-R • They can also be transformed into a wide assortment of compounds. Ch 14 | 23 of 52 • Preparation by hydration of alkenes. H2O H2SO4 H2O H2SO4 Ch 14 | 24 of 52 • Aldehyde and ketone reduction (adding hydrogen across the double bond) reactions: O 1. NaBH4, ethanol 2. H3O+ R O 1. NaBH4, ethanol R R 2. H3O+ Ch 14 | 25 of 52 Reactions of Alcohols Combustion 2CH3OH + 3O2 2CO2 + 4H2O + Heat Dehydration H OH H+, heat H-C-C-H H H alcohol H-C=C-H + H2O H H alkene Ch 14 | 26 of 52 Alcohols, Phenols, and Ethers cont’d ← Fig. 14.12 In an intramolecular alcohol dehydration the components of water are removed from neighboring carbon atoms. This is an elimination reaction. Ch 14 | 27 of 52 Reactions of Alcohols: Dehydration • Dehydration of an alcohol produces an _________ • Phenols __________ undergo dehydration • Zaitsev’s rule – The major product in an intramolecular alcohol dehydration reaction is the ________ that has the greatest number of alkyl groups attached to the carbon atoms of the double bond OH H2O, 50 oC H2SO4 H2O, 50 oC H2SO4 HO Ch 14 | 28 of 52 Reactions of Alcohols: Intermolecular Alcohol Dehydration • Ethers form when two alcohols dehydrate at a ____ temperature (140oC) – H3C-OH + HO-CH3 H3C-O-CH3 + H2O – Two methanol dimethyl ether + water – Note: Dehydration to an alkene at _____oC Ch 14 | 29 of 52 Reactions of Alcohols: Oxidation and Reduction • In organic chemistry, an easy way to recognize oxidation: – An increase in the number of C-O bonds OR – A loss of hydrogen atoms • In organic chemistry, an easy way to recognize reduction: – A decrease in the number of C-O bonds OR – A gain of hydrogen atoms Ch 14 | 30 of 52 • Oxidation of alcohols. • Valuable reaction to yield carbonyl (C=O) compounds. – Product depends on starting alcohol and amount of oxidizer. O OH O Oxidizing agent R O OH Ch 14 | 31 of 52 O • Oxidation of alcohols. – Primary alcohols yield aldehydes and carboxylic acids. – Secondary alcohols yield ketones. – Tertiary alcohols do not react. From primary alcohols O From primary alcohols OH O From secondary alcohols Ch 14 | 32 of 52 • Oxidation reactions: O OH PCC* CH2Cl2 R R O OH CrO3, H3O+ or Na2Cr2O7, H2O, CH3CO2H R R OH O OH CrO3, H3O+ R R or Na2Cr2O7, H2O, CH3CO2H R R R-OH R(CO)R or RCHO RCOOH * PCC = Pyridinium chlorochromate Ch 14 | 33 of 52 • Levels of oxidation of secondary alcohols: – Ketone (Most oxidized) – Alcohol (Least oxidized) • Levels of oxidation of primary alcohols: – Carboxylic Acid (Most oxidized) – Aldehyde – Alcohol (Least oxidized) O OH Least Oxidized OH Most Oxidized O O OH Ch 14 | 34 of 52 Reactions of Alcohols: Halogenation • Substitution reactions – Halogen replaces the hydroxyl group – Reactants: Phosphorus trihalides (with heat) – 3R-OH + PX3 3R-X + H3PO3 Ch 14 | 35 of 52 Ch 14 | 36 of 52 Chemistry at a Glance: Summary of Reactions Involving Alcohols Ch 14 | 37 of 52 Phenols → Fig. 14.14 Phenol molecule Ch 14 | 38 of 52 • Phenols. – Phenols are named as seen in Chapter 13. – Use “phenol” as the parent name instead of benzene. OH H3C Ch 14 | 39 of 52 Phenols in Medicine Phenols are weak acids and are used as antiseptics OH OH OH OH OH CH2CH2CH2CH2CH2CH3 Phenol Resorcinol (antiseptic) 4-Hexylresorcinal (antiseptic) Ch 14 | 40 of 52 Ethers → Fig. 14.17 The similar shapes of water and dimethyl ether molecules. Ch 14 | 41 of 52 Ethers ← Fig. 14.18 Alcohols and ethers with the same number of carbon atoms and the same degree of saturation are structural isomers. Ch 14 | 42 of 52 CC 14.3 Marijuana Ch 14 | 43 of 52 PHEW ! → Fig. 14.21 Thiols are responsible for the strong odor of "essence of skunk.“ What is the chemical composition of a thiol, and how does it relate to alcohols? Thiols contain sulfur, in particular a R–S-H group. Jeff Lepore/Photo Researchers Ch 14 | 44 of 52 Ch 14 | 45 of 52 Alcohols, Phenols, and Ethers cont’d Ch 14 | 46 of 52 Thiols Many thiols have disagreeable odors Used to detect gas leak Found in onions, oysters, garlic and oysters Onions CH3CH2CH2-SH 1-propanethiol Garlic CH2= CHCH2-SH 2-propene-1-thiol Skunk spray CH3 trans-2-butene-1-thiol CH = CH CH2SH Ch 14 | 47 of 52 Alcohols, Phenols, and Ethers cont’d ← Fig. 14.22 A comparison involving dimethyl ether and demethyl sulfide. Ch 14 | 48 of 52 Properties of Ethers • • • • • Non-polar Low boiling points Anesthetic (diethylether) Flammable React slowly with oxygen to form unstable hydroperoxides and perioxides • However, generally unreactive Ch 14 | 49 of 52 Ethers • Contain an oxygen atom between ______ carbon atoms • Simple ethers are named by listing the alkyl names in alphabetical order followed by “ether” – CH3-O-CH3 – CH3-O-CH2CH3 – CH3-CH2-O-CH2CH3 Ch 14 | 50 of 52 • Ethers (naming). – Simple ethers that contain no other functional groups: name the two organic groups and add the word “ether.” – Otherwise, use “alkoxy” as the substituent name. O O O O Ch 14 | 51 of 52 Ethers as Anesthetics Anesthetics inhibit pain signals to the brain CH3CH2-O-CH2CH3 used for over a century (Morton, 1846) Causes nausea and is highly flammable 1960s developed nonflammable anesthetics Cl F F Cl F H H-C-C-O-C-H F F F Ethane(enflurane) H-C-C-O-C-H H F H Penthrane Ch 14 | 52 of 52