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Chapter 12 Organic Compounds with Oxygen and Sulfur 1 Alcohols An alcohol contains a hydroxyl group (–OH) that replaces a hydrogen atom in a hydrocarbon. A phenol contains a hydroxyl group (–OH) attached to a benzene ring. 2 Naming Alcohols The names of alcohols • in the IUPAC system replace the -e with -ol • with common names use the name of the alkyl group followed by alcohol Formula IUPAC CH4 methane CH3─OH methanol CH3─CH3 ethane CH3─CH2─OH ethanol Common Name methyl alcohol ethyl alcohol Naming Alcohols 4 Naming of Alcohols Step 1 Name the longest carbon chain with the –OH group. Name an aromatic alcohol as a phenol. CH3CH2CH2OH propanol OH CH3CHCH2CH3 CH3 butanol OH CH3CHCH2CH2CHCH3 6 5 4 3 2 1 5 hexanol Naming of Alcohols Step 2 Number the chain starting at the end closer to the –OH. CH3CH2CH2OH 1-propanol OH CH3CHCH2CH3 CH3 2-butanol OH CH3CHCH2CH2CHCH3 6 5 4 3 2 1 6 2-hexanol Naming of Alcohols Step 3 Give the location and name of each substituent relative to the –OH group. CH3CH2CH2OH 1-propanol OH CH3CHCH2CH3 CH3 2-butanol OH CH3CHCH2CH2CHCH3 6 5 4 3 2 1 7 5-methyl-2-hexanol Some Typical Alcohols OH | “Rubbing alcohol” CH3—CH—CH3 2-propanol (isopropyl alcohol) Antifreeze HO—CH2—CH2—OH 1,2-ethanediol (ethylene glycol) OH | Glycerol HO—CH2—CH—CH2—OH 1,2,3-propanetriol 8 Learning Check Name the following compounds: 1. CH3—CH2—CH2—CH2—OH 2. OH CH3 | | CH3—CH—CH—CH2—CH3 OH 3. 9 Solution Step 1 Name the longest carbon chain with the –OH group. Name an aromatic alcohol as a phenol. 1. CH3—CH2—CH2—CH2—OH butanol OH CH3 | | 2. CH3—CH—CH—CH2—CH3 pentanol OH 3. cyclopentanol 10 Solution Step 2 Number the chain starting at the end closer to the –OH. 1. CH3—CH2—CH2—CH2—OH 1-butanol OH CH3 | | 2. CH3—CH—CH—CH2—CH3 2-pentanol OH 3. cyclopentanol 11 Solution Step 3 Give the location and name of each substituent relative to the –OH group. 1. CH3—CH2—CH2—CH2—OH 1-butanol OH CH3 | | 2. CH3—CH—CH—CH2—CH3 3-methyl-2-pentanol OH 3. cyclopentanol 12 Phenols in Medicine Phenol is • the IUPAC name for benzene with a hydroxyl group • used in antiseptics and disinfectants OH OH OH OH OH CH2CH2CH2CH2CH2CH3 Phenol Resorcinol 4-Hexylresorcinol 13 Derivatives of Phenol Compounds of phenol are the active ingredients in the essential oils of cloves, vanilla, nutmeg, and mint. 14 Naming Phenols Step 1 Name the longest carbon chain with the –OH group. Name an aromatic alcohol as a phenol. OH OH Cl Br phenol phenol 15 Naming Phenols Step 2 Number the chain starting at the end closer to the –OH. OH OH 1 1 3 4 Cl Br phenol phenol 16 Naming Phenols Step 3 Give the location and name of each substituent relative to the –OH group. OH OH 1 1 3 4 Cl Br 3-chlorophenol 4-bromophenol 17 Thiols Thiols • contain sulfur • are similar to alcohols • contain a thiol (–SH) group • often have strong odors • are found in cheese, onions, garlic, and oysters • are used to detect gas leaks 18 Thiols Thiols are named in the IUPAC system by adding thiol to the alkane name of the longest carbon chain. 19 Ethers An ether • contains an –O– between two carbon groups • has a common name that gives the alkyl names of the attached groups, followed by ether CH3OCH3 CH3CH2OCH3 20 Learning Check Write the structure of the following: A. 3-pentanol B. ethanethiol C. diethyl ether 21 Solution A. 3-pentanol OH | CH3CH2CHCH2CH3 B. ethanethiol CH3CH2SH C. diethyl ether CH3CH2OCH2CH3 22 Ethers as Anesthetics Anesthetics • inhibit pain signals to the brain • like diethyl ether, CH3CH2OCH2CH3, were used for over a century, but caused nausea and were flammable • developed by the 1960s were nonflammable Cl F F Cl F H HCCOCH F F F Ethrane (enflurane) 23 HCCOCH H F H Penthrane Classification of Alcohols Classification of alcohols is • determined by the number of alkyl groups attached to the carbon bonded to the hydroxyl • primary (1), secondary (2), or tertiary (3) Primary (1) 1 group H | CH3—C—OH | H 24 Secondary (2) 2 groups CH3 | CH3—C—OH | H Tertiary (3) 3 groups CH3 | CH3—C—OH | CH3 Solubility of Alcohols in Water Alcohols • contain polar OH groups and form hydrogen bonds with other alcohol molecules • that have one to three carbons are soluble in water • solubility in water decreases with increasing number of carbons 25 Solubility of Ethers in Water Ethers • do not have a polar OH group, but have a COC group • do not form hydrogen bonds • with less than four carbons are slightly soluble in water • with more than four carbons are not soluble in water 26 Solubility of Phenols Phenols • are slightly soluble in water • have an OH group that can form hydrogen bonds with water • can react with water to produce phenoxide ions • were once used as antiseptics OH O- + H2O + H3O+ 27 Learning Check Indicate whether each of the following is soluble in water and explain why. A. CH3CH2CH2CH2CH2CH2OH B. CH3OCH2CH3 C. CH3CH2OH 28 Solution Indicate whether each of the following is soluble in water and explain why. A. CH3CH2CH2CH2CH2CH2OH Not soluble Alcohols with long carbon chains (nonpolar) are not soluble. B. CH3OCH2CH3 Slightly soluble Ethers with less than four carbons are only slightly soluble in water. C. CH3CH2OH Soluble Short-chain alcohols form hydrogen bonds with water. 29 Dehydration of Alcohols Alcohols undergo • dehydration when heated with an acid catalyst • the loss of –H and –OH from adjacent carbon atoms, producing an alkene H OH | | H—C—C—H | | H H alcohol 30 H+, heat H—C=C—H + H2O | | H H alkene Oxidation of 1 Alcohols Alcohols undergo oxidation, increasing the number of carbon and oxygen bonds. Primary alcohols are oxidized to produce an aldehyde. 1 bond to O H OH | | H—C—C—H | | H H 1 alcohol 31 2 bonds to O H O | || H—C—C—H | oxidation H aldehyde Oxidation of 1 Alcohols Alcohols undergo oxidation, increasing the number of carbon and oxygen bonds. Aldehydes can further oxidize to produce a carboxylic acid. 1 bond to O H O | || H—C—C—H | H aldehyde 32 2 bonds to O H O | || H—C—C—OH | oxidation H carboxylic acid Oxidation of 2 Alcohols Secondary alcohols are oxidized to produce a ketone. To indicate the process of oxidation, [O] is placed over the reaction arrow. 1 bond to O H OH H | | | H—C—C—C—H | | | H H H 2 alcohol 33 2 bonds to O [O] H O H | || | H—C—C—C—H | | H H ketone Oxidation of Tertiary 3 Alcohols Tertiary (3) alcohols do not readily oxidize. OH CH3CCH3 CH3 3 alcohol 34 [O] no product no H to oxidize no reaction 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 a decrease in the number of C–O bonds • there is a gain of H 35 Methanol Poisoning Methanol • is also known as methyl alcohol • is highly toxic and found in windshield washer fluid, Sterno, and paint strippers • is rapidly absorbed and oxidized to formaldehyde and then formic acid O O [O] [O] CH3OH HCH HCOH methyl alcohol formaldehyde 36 formic acid Ethanol, CH3CH2OH Ethanol • acts as a depressant and 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 37 Effect of Alcohol on the Body 38 Oxidation of Thiols When thiols undergo oxidation, • an H atom is lost from each of two –SH groups • the product is a disulfide • protein in hair is cross-linked by disulfide bonds found in the amino acid cysteine 39 Learning Check Give the primary product for the reaction of 2-propanol when it undergoes A. oxidation B. dehydration 40 Solution OH CH3CHCH3 = 2-propanol = C3H8O A. oxidation OH 2CH3CHCH3 + 9O2 B. dehydration OH CH3CHCH3 41 [O] H+, heat O CH3CCH3 + 6CO2 + 8H2O CH3CH=CH2 + H2O Carbonyl Group in Aldehydes and Ketones A carbonyl group • consists of a carbon-oxygen polar double bond • has a very electronegative oxygen atom • has two lone pair electrons on the O atom • has partial positive charge on C and partial negative charge on O O C 42 Carbonyl Group in Aldehydes and Ketones A carbonyl group • in an aldehyde is attached to at least one H atom • in a ketone is attached to two carbon groups 43 Naming Aldehydes An aldehyde • has an IUPAC name in which the -e in the alkane name is changed to -al • has a common name for the first four aldehydes that use the following prefixes: 1 carbon, form 2 carbons, acet 3 carbons, propion 4 carbons butyr followed by aldehyde 44 Naming Aldehydes 45 Naming Aldehydes 46 Naming Aldehydes Give the IUPAC name for the following aldehydes: O || CH3CH2CH2CHCH | CH3 O C H Cl Cl 47 Naming Aldehydes Step 1 Name the longest carbon chain containing the carbonyl group by replacing the e in the alkane name with al. O O || CH3CH2CH2CHCH | CH3 pentanal 48 C H Cl Cl benzaldehyde Naming Aldehydes Step 2 Name and number substituents by counting the carbonyl group as carbon 1. O || CH3CH2CH2CHCH | CH3 2-methylpentanal O C H Cl Cl 3,4-dichlorobenzaldehyde 49 Aldehydes in Flavorings Several naturally occurring aldehydes are used as flavorings for foods and fragrances. O O C C H H vanillin HO OCH3 benzaldehyde (almonds) O C HC C H H cinnamaldehyde cinnamon 50 Naming Ketones When naming the following ketones • in the IUPAC system, the -e in the alkane name is replaced with -one • with a common name, the alkyl groups attached to the carbonyl group are named alphabetically, followed by ketone O CH3 CCH3 propanone (dimethyl ketone) 51 O CH3CCH2CH3 2-butanone (ethyl methyl ketone) Naming Ketones 52 Naming Ketones Name the following ketones using the IUPAC system. O || CH3CH2CHCH2CCH3 | CH3 O CH3 CH3 53 Naming Ketones Step 1 Name the longest carbon chain that contains the carbonyl group by replacing the e in the alkane name with one. O O || CH3CH2CHCH2CCH3 | CH3 hexanone 54 CH3 CH3 pentanone Naming Ketones Step 2 Number the carbon chain starting from the end nearer the carbonyl group and indicate its location. O || CH3CH2CHCH2CCH3 | CH3 2-hexanone O CH3 CH3 pentanone 55 Naming Ketones Step 3 Name and number any substituents on the carbon chain. O || CH3CH2CHCH2CCH3 | CH3 4-methyl-2-hexanone O CH3 CH3 2,3-dimethylcylcopentanone 56 Ketones in Common Use Acetone (propanone) is a solvent used in nail polish remover. Butanedione is the butter flavoring used in margarine. 57 Physical Properties The polar carbonyl group provides dipole-dipole interactions. + - + - C=O C=O Because the electronegative oxygen atom forms hydrogen bonds with water molecules, aldehydes and ketones with one to four carbons are very soluble. 58 Solubility of Aldehydes and Ketones in Water 59 Solubility in Water The electronegative O atom of the carbonyl group of aldehydes and ketones forms hydrogen bonds with water. 60 Oxidation of Aldehydes Primary alcohols can be oxidized to aldehydes, which can be easily oxidized to carboxylic acids. Secondary alcohols can be oxidized to ketones, which cannot be further oxidized. 61 Tollens’ Test In Tollens’ test, • Tollens’ reagent, which contains Ag+, oxidizes aldehydes but not ketones. • Ag+ is reduced to metallic Ag, which appears as a “mirror” in the test tube. 62 Tollens’ Test 63 Benedict’s Test In Benedict’s test, Benedict’s reagent, which contains Cu2+, reacts with aldehydes that have an adjacent OH group. Monosaccharide sugars typically have this aldehyde – adjacent hydroxide arrangement. 64 Benedict’s Test In Benedict’s test, • an aldehyde is oxidized to a carboxylic acid, while Cu2+ is reduced to give red Cu2O(s). The blue Cu2+ in Benedict’s solution forms a brick-red solid of Cu2O in a positive test for many sugars and aldehydes with adjacent hydroxyl groups. 65 Reduction of Aldehydes and Ketones Aldehydes and ketones can be reduced by sodium borohydride, NaBH4, or H2. The reduction of aldehydes and ketones decreases the number of carbon–oxygen bonds by addition of hydrogen or loss of oxygen. 66 Isomers Molecules are structural isomers when they have the same molecular formula, but different bonding arrangements. 67 Stereoisomers Stereoisomers have identical molecular formulas, but they are not structural isomers. In stereoisomers, the atoms are bonded in the same sequence but differ in the way they are arranged in space. When stereoisomers have mirror images that are different, they are said to have “handedness.” 68 Chiral Molecules Have Handedness Chiral molecules • have the same number of atoms arranged differently in space • have one or more chiral carbon atoms, each of which is bonded to four different groups • are like your hands Try to superimpose your thumbs, palms, back of hands, and little fingers. 69 Some Everyday Chiral and Achiral Objects 70 Chiral Carbon Atoms Are Mirror Images • The mirror images of chiral compounds cannot be superimposed. • When the H and I atoms are aligned, the Cl and Br atoms are on opposite sides. 71 Achiral Structures Are Superimposable When the mirror image of an achiral structure is rotated, the structure can be aligned with the initial structure. Thus this mirror image is superimposable. 72 Learning Check Identify each as a chiral or an achiral compound. Cl Cl H C C H3 C H 2C H 3 A. H C Cl C H3 H C H Br B. C. C H3 73 Solution Identify each as a chiral or an achiral compound. Cl Cl H C C H3 H C Cl C H3 H C C H3 H Br A. B. C. chiral achiral chiral C H 2C H 3 74 Fischer Projections A Fischer projection • is a two-dimensional representation of a three-dimensional molecule • places the most oxidized group at the top • uses vertical lines in place of dashes for bonds that go back • uses horizontal lines in place of wedges for bonds that come forward 75 Drawing Fischer Projections 76 D and L Notations • By convention, the letter L is assigned to the structure with the –OH on the left. • The letter D is assigned to the structure with the –OH on the right. 77 Learning Check Indicate whether each pair is a mirror image that cannot be superimposed (enantiomers). CH2OH A. B. H H C CH3 CH2OH and CH3 C Br Br Cl Cl C H CH3 and CH3 C H H H 78 Solution Indicate whether each pair is a mirror image that cannot be superimposed (enantiomers). CH2OH A. B. H H C CH3 CH2OH and CH3 C Br Br Cl Cl C H CH3 and CH3 C H Yes No H H 79 Concept Map – Organic Molecules with O and S 80