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Alcohols, Phenols, Ethers, and Thiols 14 Answers and Solutions to Text Problems 14.1 In a primary (1°) alcohol the carbon bonded to the hydroxyl group (OH) is attached to one alkyl group except for methanol; to two alkyl groups in a secondary alcohol (2°); and to three alkyl groups in a tertiary alcohol (3°). a. 1° b. 1° c. 3° d. 2° e. 3° 14.2 a. secondary d. tertiary 14.3 a. This compound has a two-carbon chain (ethane). The final −e is dropped and −ol added to indicate an alcohol. The IUPAC name is ethanol. b. This compound has a four-carbon chain with a hydroxyl attached to carbon 2. The IUPAC name is 2-butanol. c. This compound has a six-carbon chain with a hydroxyl group attached to carbon 3. The IUPAC name is 3-hexanol. d. This compound has a four-carbon chain with a hydroxyl attached to carbon 1and a methyl attached to carbon 3. The IUPAC name is 3-methyl-1-butanol. e. This compound is a six-carbon cycloalkane with a hydroxyl attached to carbon 1 and two methyl groups, one attached to carbon 3 and the other to carbon 4. Since the hydroxyl is always attached to carbon 1 the number 1 is omitted in the name. The IUPAC name is 3,4-dimethylcyclohexanol. f. This compound has a seven-carbon chain with a hydroxyl attached to carbon 1 and three methyl groups, one attached to carbon 3 and two attached to carbon 5. The IUPAC name is 3,5,5-trimethyl-1-heptanol 14.4 a. 1-ethylcyclobutanol c. 2,3-dimethyl-1-pentanol e. 2,4-dimethylcyclopentanol b. primary e. primary c. primary b. 3-chloro-2-methyl-1-butanol d. 5,5-dichloro-2-pentanol f. 3-ethyl-1-pentanol Chapter 14 Answers and Solutions 14.5 a. 1-propanol has a three-carbon chain with a hydroxyl attached to carbon 1. CH3CH2CH2OH b. Methyl alcohol has a hydroxyl attached to a one-carbon alkane CH3OH. c. 3-pentanol has a five-carbon chain with a hydroxyl attached to carbon 3. OH | CH3CH2CHCH2CH3 d. 2-methyl-2-butanol has a four-carbon chain with a methyl and hydroxyl attached to carbon 2. OH | CH3CCH2CH3 | CH3 OH e. Cyclohexanol has a six-carbon cycloalkane with a hydroxyl attached. f. 1,4-butanediol has a four-carbon chain (butane). The diol indicates that there are two hydroxyl groups, one attached to carbon 1 and one to carbon 4. HOCH2CH2CH2CH2OH CH3 14.6 a. CH3CH2OH b. CH3CHCH2CH2OH OH Cl c. d. CH3CH2CH2OH Cl CH3 OH CH3 OH f. CH3CCHCHCH2CH3 CH3 e. OH 14.7 A benzene ring with a hydroxyl group is called phenol. Substituents are numbered from the carbon bonded to the hydroxyl group as carbon 1. Common names use the prefixes ortho,meta, and para. a. phenol b. 2-bromophenol, ortho-bromophenol (Groups on the 1 and 2 positions are ortho) c. 3,5-dichlorophenol d. 3-bromophenol, meta-bromophenol (Groups on the 1 and 3 positions are meta) 14.8 a. 3-ethylphenol, m-ethylphenol c. 3-chlorophenol, m-chlorophenol b. 2,5-dibromophenol d. 2-chlorophenol, o-chlorophenol Alcohols, Phenols, Ethers, and Thiols 14.9 a. The m (meta) indicates that the two groups are in the 1,3 arrangement. OH OH Br b. The p (para) indicates that the two groups are in the 1,4 arrangement Cl c. Two chlorine atoms are attached to the aromatic system, one on carbon 2 and the other on carbon 5, with the hydroxyl attached to carbon 1. OH Cl Cl d. The o (ortho) indicates that the two groups are in the 1,2 arrangement OH e. The name indicated that there is an ethyl group on carbon 4 with the hydroxyl on carbon 1. OH CH2CH3 14.10 OH OH a. b. Cl c. OH CH2CH3 CH3 Cl CH3 OH OH CH2CH3 d. CH3 e. Chapter 14 Answers and Solutions 14.11 a. This is a one-carbon alkane with a thiol (−SH) group. The IUPAC name is methanethiol. b. This thiol has a three-carbon alkane with the thiol group attached to carbon 2. The IUPAC name is 2-propanethiol c. This compound has a four-carbon alkane with methyl groups attached to carbon 2 and carbon 3 and the thiol attached to carbon 1. The IUPAC name is 2,3-dimethyl-1-butanethiol. d. This compound has a thiol attached to a cyclobutane. The IUPAC name is cyclobutanethiol. 14.12 a. 1-propanethiol c. 2,2-dimethyl-1-propanethiol 14.13 a. ethanol 14.14 a. 1,2-ethanediol; ethylene glycol forms oxalic acid b. BHA; butylated hydroxyanisole and BHT; butylated hydroxytoluene c. 1,2,3-propanetriol; glycerol 14.15 a. methoxyethane; ethyl methyl ether b. methoxycyclohexane, cyclohexyl methyl ether c. ethoxycyclobutane, cyclobutyl ethyl ether d. 1-methoxypropane, methyl propyl ether 14.16 a. 1-ethoxypropane, ethyl propyl ether b. b. 2-pentanethiol d. cyclopentanethiol thymol c. ethoxycyclopentane, cyclopentyl ethyl ether 14.17 c. ortho-phenylphenol b. methoxybenzene, methyl phenyl ether; anisole d. methoxymethane, dimethyl ether a. Ethyl propyl ether has a two-carbon group and a three-carbon group attached to oxygen by single bonds. CH3CH2OCH2CH2CH3 b. Ethyl cyclopropyl ether has a two-carbon group and a three-carbon cyclo alkyl group attached to oxygen by single bonds. CH3CH2O c. Methoxycyclopentane has a one-carbon group and a five-carbon cycloalkyl group attached to oxygen by single bonds. OCH3 d. 1-ethoxy-2-methylbutane has a four-carbon chain with a methyl attached to carbon 2 and an ethoxy attached to carbon 1. CH3 | CH3CH2−O−CH2CHCH2CH3 e. 2,3-dimethoxypentane has a five-carbon chain with two methoxy groups attached; one to carbon 2 and the other to carbon 3. OCH3 | CH3CHCHCH2CH3 | OCH3 Alcohols, Phenols, Ethers, and Thiols 14.18 a. CH3CH2−O−CH2CH3 b. O OCH2CH3 c. CH3 CH3 d. CH3CCHCH3 OCH3 OCH3 OCH3 e. 14.19 a. Constitutional isomers (C5H12O) have the same formula, but different arrangements. b. Different compounds have different molecular formulas. c. Constitutional isomers (C5H12O) have the same formula, but different arrangements. 14.20 a. constitutional isomers 14.21 The heterocyclic ethers with five atoms including one oxygen are named furan; six atoms including one oxygen are pyrans. A six-atom cyclic ether with two oxygen atoms is dioxane. a. tetrahydrofuran b. 3-methylfuran c. 5-methyl-1, 3-dioxane 14.22 a. furan 14.23 a. methanol; hydrogen bonding of alcohols gives higher boiling points than alkanes. b. 1-butanol; alcohols hydrogen bond, but ethers cannot. c. 1-butanol; hydrogen bonding of alcohols gives higher boiling points than alkanes. 14.24 Glycerol can form more hydrogen bonds because it has three hydroxyl groups (OH) compared to the hydrogen bond for one hydroxyl group in 1-pentanol. 14.25 a. b. c. d. e. 14.26 a. Ethanol contains a hydroxyl group (OH) b. The oxygen in ethers can form hydrogen bonds with water. c. Alcohols with one to four carbon atoms are soluble in water. In alcohols with longer carbon chains, the effect of the OH group is diminished. 14.27 Dehydration is the removal of an −OH and a −H from adjacent carbon atoms. b. constitutional isomers b. 2-methyl-1,4-dioxane c. constitutional isomers c. 4-methylpyran yes, alcohols with 1-4 carbon atoms hydrogen bond with water yes; the water can hydrogen bond to the O in ether no; a carbon chain longer than 4 carbon atoms diminishes the effect of the OH group. no; alkanes are nonpolar and do not hydrogen bond yes; the OH in phenol ionizes in water, which makes it soluble a. CH3CH2CH=CH2 b. c. In c, there are two possible products A and B. B will be the major product, since the hydrogen is removed from the carbon that has the smaller number of hydrogens. CH3 A B CH3 Chapter 14 Answers and Solutions d. In d, there are two possible products A and B. B will be the major product, since the hydrogen is removed from the carbon that has the smaller number of hydrogens. CH3CH2CH2CH=CH2 CH3CH2CH=CHCH3 A B CH3 CH3 14.28 a. CH3C=CH2 b. CH3 CH=CCH2CH3 CH3 c. 14.29 d. An ether is formed when H2O is eliminated from two alcohols; the alkyl portion of one alcohol combines with the alkoxy portion of the other alcohol. b. CH3CH2CH2OCH2CH2CH3 a. CH3OCH3 CH3 CH3 b. CH3CHCH2OCH2CHCH3 14.30 a. CH3CH2OCH2CH3 14.31 Alcohols can produce alkenes and ethers by the loss of water (dehydration). a. CH3CH2OH b. Since this ether has two different alkyl groups;,it must be formed from two alcohols. CH3OH + CH3CH2OH c. 14.32 14.33 OH a. CH3CH2OH CH3 CH3 b. CH3CCH2CH3 or CH3CHCHCH3 OH OH OH c. a. A primary alcohol oxidizes to an aldehyde and then to a carboxylic acid. O O || || CH3CH2CH2CH2CH then CH3CH2CH2CH2COH O || b. A secondary alcohol oxidizes to a ketone. CH3CH2CCH3 c. A secondary alcohol oxidizes to a ketone. O Alcohols, Phenols, Ethers, and Thiols O CH3 || | d. A secondary alcohol oxidizes to a ketone. CH3CCH2CHCH3 e. A primary alcohol oxidizes to an aldehyde and then to a carboxylic acid. O CH3 O CH3 || | || | CH3CHCH2CH then CH3CHCH2COH O 14.34 a. C OH O CH3 || b. CH3CHCH2 CCH3 O O O || || d. CH3CCCH2CH3 14.35 c. none e. a. An aldehyde is the product of the oxidation of a primary alcohol CH3 OH. b. A ketone is the product of the oxidation of a secondary alcohol. OH OH | c. A ketone is the product of the oxidation of a secondary alcohol. CH3CHCH2CH3 d. An aldehyde is the product of the oxidation of a primary alcohol. CH2OH OH e. A ketone is the product of the oxidation of a secondary alcohol. CH3 a. CH3CH2OH OH CH3 | | b. CH3CHCHCH3 d. CH3CH2CH2OH CH3 | e. CH3CHCH2CH2OH 14.37 a. 2° c. 1° 14.38 a. tertiary d. tertiary 14.36 b. 1° b. tertiary e. primary d. 2° c. primary f. secondary OH c. e. 1° f. 3° Chapter 14 Answers and Solutions 14.39 a. alcohol e. ether b. ether f. cyclic ether c. thiol g. alcohol d. alcohol h. phenol 14.40 a. phenol e. ether b. thiol f. cyclic ether c. ether g. phenol d. alcochol h. phenol 14.41 a. c. e. g. 2-chloro-4-methylcyclohexanol 2-propanethiol 1-methoxypropane; methyl propyl ether 4-bromo-2-pentanol b. methyoxy benzene; methyl phenyl ether d. 2,4-dimethyl-2-pentanol f. 3-methyl furan h. meta-cresol 14.42 a. c. e. g. 4-chlorophenol; p-chlorophenol ethoxycyclopentane; cyclopentyl ethyl ether 3-methoxypentane 2,4-dichlorophenol b. d. f. h. 1-propanethiol 2,4-dimethyl-2-pentanol 1.4-dioxane 3,4-dimethylphenol 14.43 OH OH a. b. CH3 c. H3C CH3 OH CH CH Cl O d. CH2 CH2 CH3 CH3 SH e. CH3 CH2 CH CH2 f. CH3 CH3 OH OH Br g. Br 14.44 OCH3 | a. CH3CH2CHCH2CH3 OH OH | | c. CH3CHCHCH2CH3 OH CH3 | | f. CH3CHCHCH3 OH b. Cl d. CH3CH2CH2OCH3 OH g. Cl Cl e. CH3SH Alcohols, Phenols, Ethers, and Thiols 14.45 a. Glycerol is used in skin lotions. b. 1,2-ethanediol; ethylene glycol is used in antifreeze c. Ethanol is produced by fermentation of grains and sugars. 14.46 a. methanol 14.47 Write the carbon chain first, and place the OH on the carbon atoms in the chain to give different structural formulas. Shorten the chain by one carbon, and attach a methyl group and OH group to give different compounds. OH | CH3CH2CH2CH2OH CH3CHCH2CH3 b. 2-propanol; isopropyl alcohol CH3 | CH2CHCH2OH 14.48 OH | CH2CCH3 | CH3 CH3OCH2CH2CH2CH3 CH3 | CH3OCH2CHCH3 CH3 | CH3OCCH3 c. ethanol CH3CH2OCH2CH2CH3 CH3 | CH3CH2OCHCH3 CH3 | CH3OCHCH2CH3 14.49 a. 1-propanol; hydrogen bonding c. 1-butanol; larger molar mass b. 1-propanol; hydrogen bonding 14.50 a. ethyl alcohol c. 1-butanol 14.51 a. c. a. c. 14.52 14.53 b. 2-pentanol soluble; hydrogen bonding b. soluble; hydrogen bonding insoluble; long carbon chain diminishes effect of polar OH on hydrogen bonding soluble; three OH groups b. insoluble; nonpolar hydrocarbon soluble; two OH groups makes longer hydrocarbon chain more soluble in water a. CH3CH=CH2 O || b. CH3CH2CH O c. CH3CH=CHCH3 || d. CH3CH2CCH3 e. CH3CH2CH2O CH2CH2CH3 O f. g. Chapter 14 Answers and Solutions 14.54 CH3 | a. CH3C=CH2 CH3 | b. CH3C=CHCH3 CH3 O | || c. CH3CHCCH3 CH3 d. O CH3 f. CH3CH2OCH2CH3 e. g. CH3CH2CH=CHCH3 14.55 Cl | H+, heat a. CH3CH2CH2OH → CH2CH=CH2 + HCl → CH3CHCH3 OH H+, heat Pt → CH3C=CH2 + H2 → CH3CHCH3 | | CH3 CH3 OH H+ | H+, heat c. CH3CH2CH2OH → CH3CH=CH2 + H2O → CH3 CHCH3 | b. CH3CCH3 | CH3 O || [O] → CH3CCH3 14.56 a. CH3CH2CH2CH2CH2OH b. OH H+, heat → CH3CH2CH2CH=CH2 Cl H + HCl H+, heat c. CH3CH2CH2CH2OH → CH3CH2CH=CH2 + Cl2 → Cl | CH3CH2CHCH2Cl 14.57 Testosterone contains cycloalkene, alcohol and ketone functional groups. 14.58 a. cycloalkene, phenol, ether b. cycloalkene, ketone, alcohol, alkyne Alcohols, Phenols, Ethers, and Thiols 14.59 4-hexyl-1, 3-benzenediol tells us that there is a six carbon group attached to carbon 4 of a benzene OH ring and hydroxyls attached to carbons 1 and 3. OH CH2CH2CH2CH2CH2CH3 14.60 Menthol is 2−isopropyl−5−methylcyclohexanol. Thymol is 2−isopropyl−5−methylphenol. They have the same groups in the same position, but thymol is aromatic, while menthol is a cyclic alcohol. 14.61 a. 2,5-dichlorophenol is a benzene ring with a hydroxyl on carbon 1 and chlorine atoms on carbons 2 and 5. OH Cl Cl CH3 b. CH3 CH CH3 CH2 CH2 SH H H C C CH2 SH OH c. Cl Cl Cl Cl Cl 14.62 b.p. −24°C Dimethyl ether CH3OCH3 Ethyl alcohol CH3CH2OH b.p. 79°C The polar hydroxyl groups in ethyl alcohol form hydrogen bonds between the alcohol molecules, which requires a higher boiling point to separate them into gaseous molecule