Alcohols, Phenols, and Ethers - K. A. Boudreaux, Angelo State University, Lecture notes of Chemistry

Download Alcohols, Phenols, and Ethers - K. A. Boudreaux, Angelo State University and more Lecture notes Chemistry in PDF only on Docsity! Chapter 3 Alcohols, Phenols, and Ethers 1 Chapter Objectives: • Learn to recognize the alcohol, phenol, and ether functional groups. • Learn the IUPAC system for naming alcohols, phenols, and ethers. • Learn the important physical properties of the alcohols, phenols, and ethers. • Learn the major chemical reaction of alcohols, and learn how to predict the products of dehydration and oxidation reactions. • Learn to recognize the thiol functional group. Chapter 3 Alcohols, Phenols, and Ethers 2 Introduction • In this chapter, we will start looking at organic molecules that incorporate C—O bonds. • Oxygen is in Group 6A of the periodic table, and in most of its compounds, contains two single bonds and two lone pairs (or one double bond and two lone pairs), and is sp3-hybridized with a bent molecular shape: • The alcohol, phenol, and ether functional groups are found in a number of important naturally occurring molecules: OH HO Ethanol Menthol Cholesterol CH3CH2OH CH3CH2OCH2CH3 Diethyl ether O O Mr. Kevin A. Boudreaux Angelo State University CHEM 2353 Fundamentals of Organic Chemistry Organic and Biochemistry for Today (Seager & Slabaugh) Chapter 3 Alcohols, Phenols, and Ethers 2 3 Alcohols 4 The Hydroxy (—OH) Functional Group • The hydroxyl group (—OH) is found in the alcohol and phenol functional groups. (Note: that’s not the same as hydroxide, OH-, which is ionic.) – in alcohols, a hydroxyl group is connected to a carbon atom. – in phenols, —OH is connected to a benzene ring. (The “parent” molecule of this class is also named phenol: PhOH or C6H5OH.) • When two carbon groups are connected by single bonds to an oxygen, this is classified as the ether functional group. OR R'R OH OH an alcohol a phenol an ether Chapter 3 Alcohols, Phenols, and Ethers 5 9 Examples: Naming Alcohols and Phenols • Provide acceptable IUPAC names for the following compounds: CH3 CH2 CH2 CH2 CH2 OH CH3 CH2 CH CH2 CH3 OH CH3 CH2 CH CH CH2 OH CH3 CH3 CH3 CH2 CH2 CH CH2 CH3 CH2 OH 10 Examples: Naming Alcohols and Phenols • Provide acceptable IUPAC names for the following compounds: OH CH2CHCH3 OH OH Chapter 3 Alcohols, Phenols, and Ethers 6 11 Examples: Naming Alcohols and Phenols • Draw and name all of the possible isomers of butanol (C4H10O) 12 Nomenclature of Alcohols and Phenols • If there is more than one OH group, a counting prefix (di-, tri-, tetra-, etc.) is placed immediately in front of the suffix -ol (diol, triol, tetraol, etc.). – Usually, the final “e” of the parent hydrocarbon is not dropped (e.g., 1,2-propanediol). – The position of each alcohol group is indicated by carbon number, separated by commas (e.g., 1,3- butanediol). • For cyclic alcohols, the carbon bearing the OH is numbered as “1.” • Phenols are named after the parent compound phenol; the C bearing the OH is numbered as “1.” Chapter 3 Alcohols, Phenols, and Ethers 7 13 Examples: Naming Alcohols and Phenols • Provide acceptable IUPAC names for the following compounds: HO CH2 CH2 OH HO CH CH2 CH CH CH3 CH3 OH CH3 CH2 CH CH2 OH OH OH CH CH2 CH OH CH3 OHCH3 14 Examples: Naming Alcohols and Phenols • Provide acceptable IUPAC names for the following compounds: OH Cl OH CH2CH2CH3 CH3 OH OH Chapter 3 Alcohols, Phenols, and Ethers 10 19 Hydrogen Bonding • The oxygen-hydrogen bond is an especially polar bond because oxygen is much more electronegative than hydrogen is. • The O—H bond is therefore a polar bond, and any molecule which contains an O—H bond (like an alcohol) is a polar molecule. O H H O H H H O H O H H H O H H O H + + - 20 Physical Properties of Alcohols • The general rule in solubility is “like dissolves like.” • Since the OH group makes alcohols polar, they will mix with polar solvents like water — as long as the carbon chain is fairly short. – The longer the carbon chain, the less soluble the alcohol is. Long chain alcohols hexanol heptanol etc. Short chain alcohols methanol ethanol isopropanol Insoluble Water solubility Soluble butanol pentanol Chapter 3 Alcohols, Phenols, and Ethers 11 21 Hydrogen Bonding of Alcohols • Alcohols hydrogen-bond to water: O R H O H H H O H O H R H O R • Alcohols also hydrogen-bond to each other: O R H O R H H O R O H R H O R 22 Boiling Points of Alcohols • Because alcohols hydrogen bond to each other, they have higher boiling points than alkanes of the same molecular weight. • The boiling point of alcohols increases as the molecules become larger. Name Structure Molecular Weight Boiling Point propane CH3CH2CH3 44.09 g/mol -42.1°C dimethyl ether CH3OCH3 46.07 g/mol -24°C ethanol CH3CH2OH 46.07 g/mol 78.3°C Chapter 3 Alcohols, Phenols, and Ethers 12 23 Examples: Physical Properties of Alcohols • Arrange the following substances in order of increasing boiling point and increasing solubility in water: – 2-butanol – 2-propanol – 2-methylpropane – 2-pentanol 24 Chapter 3 Alcohols, Phenols, and Ethers 15 29 Examples: Dehydration of Alcohols • Complete the following reactions: CH3 OH H2SO4 180°C OH H2SO4 180°C CH3CH3 CH3 CH3 30 Dehydration of Alcohols to Produce Ethers • Heating alcohols (R—OH) in concentrated sulfuric acid (H2SO4) at 140°C removes a molecule of water from two alcohol molecules, causing the two “R” groups to become attached to an oxygen atom, forming an ether functional group: R OH R OH R O+ RH2SO4 140°C H2O+ CH3CH2OH + CH3CH2OH H2SO4 140°C CH3CH2OCH2CH3 diethyl ether Chapter 3 Alcohols, Phenols, and Ethers 16 31 Examples: Dehydration of Alcohols • Complete the following reactions: CH3CH2CH2OH H2SO4 140°C H2SO4 140°C CH3CHCH3 OH H2SO4 180°C CH3CHCH2CH3 OH 32 Oxidation of Alcohols to Carbonyl Compounds • An oxidation reaction occurs when a molecule loses electrons. This is usually manifested as an increase in the number of oxygen atoms or a decrease in the number of hydrogen atoms. • Some common oxidizing agents include potassium permanganate (KMnO4), chromic acid (H2CrO4), sodium dichromate (Na2Cr2O7), and other Cr6+ salts. • Alcohols can be oxidized by removing two H atoms from the molecule; the exact products of the reaction will depend on the type of alcohol. • Representation in book: R2CHOH + (O)  R2C=O + H2O • [O] = oxidation Chapter 3 Alcohols, Phenols, and Ethers 17 33 Oxidation of Alcohols to Carbonyl Compounds • Primary or secondary alcohols can be oxidized to produce compounds containing the carbonyl group (a carbon-oxygen double bond, C=O): R C O H H C O R R 1° or 2° alcohol aldehyde or ketone [O] H C O carbonyl group 34 Oxidation of 1° Alcohols • Primary alcohols are oxidized first to aldehydes, but the aldehydes are then usually oxidized into carboxylic acids. R C O H H C O R H C O R OH aldehyde 1° alcohol carboxylic acid [O] [O] H CH3CH2OH [O] ethanol CCH3 O H acetaldehyde CCH3 O OH [O] acetic acid In the body, oxidation of ethanol to acetaldehyde takes place in the liver; the acetaldehyde is further oxidized to acetyl coenzyme A, which can be used to synthesize fat or eventually be oxidized to water and carbon dioxide. Chapter 3 Alcohols, Phenols, and Ethers 20 39 Examples: Multistep Reactions • Often, transformations on organic molecules must take place in more than one step. O CH2 OH CH2CH3 CH3CHCH3 OH CH2 CH2 CH3CH2 O CH2CH3 40 Total Synthesis of Cyclooctatetraene H O O H + CH3NH2 HO O O HO O double Mannich reaction + O NCH3 N O CH3 pseudopelletierine = Na EtOH OH NCH3 NCH3 1) CH3I 2) Ag2O N(CH3)2 OH- H2SO4  (CH3)2N 1) CH3I 2) Ag2O (CH3)3N OH- Br2 Br Br (CH3)2N N(CH3)2 1) CH3I 2) Ag2O (CH3)3N N(CH3)3 OH- OH- NH(CH3)2  Cyclooctatetraene R. Wilstatter and E. Waser, Ber., 1911, 44, 3423 A. C. Cope and C. G. Overberger, J. Amer. Chem. Soc., 1947, 69, 976; 1948, 70, 1433 Chapter 3 Alcohols, Phenols, and Ethers 21 41 Some Important Alcohols 42 Some Important Alcohols Ethylene glycol antifreeze — pure ethylene glycol freezes at 11°F, but a 50:50 mixture of ethylene glycol and water freezes at -37°F; airplane de-icer; humectant (keeps other substances moist), used in ball point pen inks CH2 CH2 OH OH OH O OH Lactic acid produced from fermentation of sugars during anaerobic conditions; sour taste, found in sourdough bread, pickles, sauerkraut, sweat, etc. Cinnamic alcohol used in perfumes, particularly in lilac and other floral scents; flavoring agent, soaps, cosmetics OH Propylene glycol antifreeze, moisturizer in lotions and foods CH2 CH OH OH CH3 Chapter 3 Alcohols, Phenols, and Ethers 22 43 OH -Turpineol pine oil; perfume and bactericide used in domestic cleaners OH Menthol oil of mint; has a cooling taste; found in cough drops, shaving lotion, and mentholated tobacco Benzyl alcohol used in perfumes and flavors, cosmetics, ointments, ball point pen inks OH Vitamin A retinol OH 44 HO OH OH Glycerol / glycerin softening agent and moisturizer found is cosmetics and many foods; used to keep toothpaste moist RCO2 O2CR O2CR A triglyceride fats and oils CHO OHH HHO OHH OHH CH2OH O H HO OH H OH OH HH H OH -D-glucose Chapter 3 Alcohols, Phenols, and Ethers 25 49 Important Phenols OH ortho-phenylphenol ingredient in Lysol Other phenols are also present in Lysol; they interfere with oxidation reactions to prevent the spoiling of food. OH Cl 2-benzyl-4-chlorophenol ingredient in LysolOH CH3 CH3 Cl 4-chloro-3,5-dimethylphenol topical antiseptic OH CH3 OH CH2(CH2)4CH3 4-n-hexylresorcinol found in mouthwash, throat lozenges 50 Phenols as Preservatives OH O CH3 C CH3 CH3 CH3 BHA (butylated hydroxy anisole) 2-t-butyl-4-methoxyphenol OH CH3 C CH3 CH3 CH3 C CH3 CH3 CH3 BHT (butylated hydroxy toluene) 2,6-di-t-butyl-4-methylphenol Antioxidants used in preservation of foods, gasoline, lubricating oils, rubber, etc. O HO CH3 CH 3 CH3 CH3 Vitamin E antioxidant; prevents oxidation of lipids, red and white blood cells, polyunsaturated fatty acids, lung tissue; prevents oxidation in lungs of pollutants such as NO2 and O3 Chapter 3 Alcohols, Phenols, and Ethers 26 51 Phenols in Flavors and Fragrances OH OCH3 CHO Vanillin oil of vanilla O SH 2-Furylmethanethiol odor of coffee O OH OH OH HO Pelargonidin a flavonoid; responsible for the red colors of geraniums, ripe raspberries, and strawberries O O N O Piperine white and black pepper 52 CH3O HO N O H Capsaicin active component of red and green chili peppers, paprika HO OH Estradiol O OH Testosterone Chapter 3 Alcohols, Phenols, and Ethers 27 53 Ethers 54 Ethers • In the ether functional group, two carbon groups are connected to a single oxygen. OC C an ether OCH3 CH3 O CH CH3 CH3OCH3 CH2CH3 OCH3CH2 CH2CH3 Chapter 3 Alcohols, Phenols, and Ethers 30 59 Cyclic Ethers • Some ethers are found in cyclic structures. (A ring that contains elements other than carbon is called a heterocyclic ring.) • Tetrahydrofuran (THF) is a common solvent in organic reactions, often used in place of diethyl ether; furan and pyran turn up frequently in carbohydrate chemistry. O O furan O pyrantetrahydrofuran 60 Physical Properties of Ethers • Alcohols hydrogen-bond to each other because they have highly polar O—H bonds. • Ethers do not have O—H bonds, and so do not hydrogen-bond to each other. O R H O R H H O R O H R alcohols hydrogen bonding O R R O R R R O R O R R ethers no hydrogen bonding Chapter 3 Alcohols, Phenols, and Ethers 31 61 Physical Properties of Ethers • Ethers are slightly polar, and can hydrogen-bond to water, although very weakly, through the oxygen atom: • Ethers therefore have low boiling points, and a higher solubility in water than hydrocarbons. • Ethers are inert to most reagents, so they make good solvent for chemical reactions. • Some ethers make good anesthetics. boiling point: alcohols > ethers > alkanes water solubility: alcohols > ethers > alkanes O H H O O R R R R 62 Some Important Ethers methyl t-butyl ether (MTBE) A common gasoline additive used as an octane booster to oxygenate the gas, and make it burn with less "knocking." It has been used since 1979 as a replacement for tetraethyl lead (leaded gasoline). This additive is the subject of intense debate because of potential health hazards of drinking water contaminated with MTBE C O CH3 CH3 CH3 CH3 Ethylene oxide an epoxide H2C CH2 O O O O OO O 18-crown-6 A "crown ether" (Charles J. Pedersen, Donald J. Cram, and Jean-Marie Lehn, Nobel Prize, 1987), which is capable of binding metal ions Chapter 3 Alcohols, Phenols, and Ethers 32 63 Anesthetics O Diethyl ether first common anesthetic (Crawford W. Long, 1842 William T. G. Morton, Charles T. Jackson, 1844) F O F Cl Enflurane Nitrous oxide laughing gas first chemical anesthetic (Sir Humphrey Davy, 1800) N2O O Divinyl ether faster acting and less nauseating than diethyl ether C C Br F F F H Cl Halothane CHCl3 Chloroform (James Young Simpson, 1846; first to use anesthesia during childbirth) 64 Polyfunctional Compounds • Compounds with more than one functional group are very common in nature; these polyfunctional molecules possess all of the reactivity of their individual functional groups. HO Cholesterol CC OH H C H OH C OH H C OH H CH2 O H HO Glucose O O OH O O O O H OO OHN O O OH HO Taxol Chapter 3 Alcohols, Phenols, and Ethers 35 69 Gas Warfare Chlorine gas and phosgene are among the first agents to have been used in gas warfare. Molecular chlorine is a gas at room temperature, and heavier than air; breathing chlorine gas causes pulmonary edema (swelling from excess fluid in tissues). Phosgene is a particularly insidious poison, since symptoms may take from one to three days to appear. The gas does not have as obvious an odor as chlorine, and when inhaled, is hydrolyzed in the lungs to produce hydrochloric acid, which dissolves the membranes in the lungs. This can result in edema, blood loss, shock, and respiratory failure. Phosgene must be inhaled to be “effective,” since it cannot be absorbed through the skin. Cl2 C Cl Cl O Chlorine Phosgene 70 Gas Warfare Mustard gas is a chemical weapon first used in 1917 during World War I at the battle of Ypres. It has a sweet, agreeable odor, similar to that of mustard, but the similarity ends there. It forms painful blisters on the skin (a vesicant) on contact, and in the lungs when inhaled; symptoms usually develop anywhere from 4 to 24 hours after exposure. Exposure produces deep, itching or burning blisters, swelling of the eyelids, and possibly blindness; inhalation at high concentrations damages the mucous membranes, causing bleeding and blistering within the lungs, leading to pulmonary edema. It is also carcinogenic and mutagenic (causes damage to DNA). Mustard gas is not very soluble in water but is very soluble in fat, contributing to its rapid absorption into the skin. It easily penetrated the early forms of protective clothing and gas masks. Modern “improvements” include using longer carbon chains to make the molecule more hydrocarbon-like (and thus more fat-soluble). Nitrogen mustards have nitrogen atoms in place of the sulfur atom. S Cl Cl Mustard gas Chapter 3 Alcohols, Phenols, and Ethers 36 71 CR R H C R OH R C C R R R R 1. Dehydration of alcohols to give alkenes: H2SO4 180°C + H2O R OH R O R 2. Dehydration of alcohols to give ethers: H2SO4 140°C + H2O R C H H O H C O R H C O R OH 3. Oxidation of a primary alcohol to give an aldehyde or carboxylic acid: 1° alcohol aldehyde carboxylic acid [O] [O] Reactions of Alcohols 72 R C H R' O H C O R R' 4. Oxidation of a secondary alcohol to give a ketone: 2° alcohol ketone [O] R C R'' R' O H 5. Oxidation of a tertiary alcohol — No Reaction: NR 3° alcohol [O] Chapter 3 Alcohols, Phenols, and Ethers 37 73 R O R' O H R C H R C R' carboxylic acid C C R R' R'' R''' ether phenol ketonealdehyde C C R'R alkane alkene alkyne aromatic ring R = a carbon group R C OH CH3CH2CH3 O O O Functional Groups 74 CR O H H H CR O H H R' CR O H R'' R' CR H OH OR' CR H OR'' OR' CR R' OH OR'' CR R' OR''' OR'' primary (1°) alcohol secondary (2°) alcohol tertiary (3°) alcohol hemiacetal acetal hemiketal ketal