Organic Chemistry,6th Edition 林司 L.G.Wade,Jr. Chapter 14 I 15 ALcohols Key Notes Hydrogen bonding;Acidity;Lucas reagent; Dehydration;Williamson synthesis By Junru Wang Email:wangjr07@163.com 西北农林科技大学理学院
西北农林科技大学理学院 By Junru Wang Email: wangjr07@163.com Chapter 14 & 15 Alcohols Organic Chemistry, 6th Edition L. G. Wade, Jr. Key Notes Hydrogen bonding; Acidity; Lucas reagent ; Dehydration ; Williamson synthesis
CONTENTS Structure Properties of Alcohols Preparation of alcohols Functional group transformation ■C-C bond formation Reduction of Carbonyl Reactions of Alcohols Acid-base reactions Elimination:Dehydration to alkene ■ Synthesis of alkyl halides:Substitution to form alkyl halide Oxidation to aldehyde,ketone ■Reduction to alkane -Synthesis of mesylate and tosylates ■Esterification Williamson synthesis of ether
CONTENTS ❖Structure & Properties of Alcohols ❖Preparation of alcohols ◼ Functional group transformation ◼ C-C bond formation ◼ Reduction of Carbonyl ❖Reactions of Alcohols ◼ Acid-base reactions ◼ Elimination:Dehydration to alkene ◼ Synthesis of alkyl halides: Substitution to form alkyl halide ◼ Oxidation to aldehyde, ketone ◼ Reduction to alkane ◼ Synthesis of mesylate and tosylates ◼ Esterification ◼ Williamson synthesis of ether
Sec 1 Structure Properties of Alcohols 0.96A 0.96A 104.50 H 108.9° water water water methyl alcohol methyl alcohol methyl alcohol Copyright2010 Pearson Prentice Hall,Inc. Hydroxyl (-OH)functional group Oxygen is sp3 hybridized. The H-O-H angle in water is 104.5 The C-O-H angle in methyl alcohol is 108.9. 1、-C,O;Sp hybridized;O:不等性SP杂化 2、一O-H,C-0为极性共价键 3、-OH,-I;R-,+I
Sec 1 Structure & Properties of Alcohols ❖Hydroxyl (-OH) functional group ❖Oxygen is sp3 hybridized. ❖The H—O—H angle in water is 104.5° . ❖The C—O—H angle in methyl alcohol is 108.9° . 1、－C，O； SP3 hybridized; O:不等性SP3杂化 2、－O-H，C-O为极性共价键 3、－OH, -I; R-, +I
Physical Properties H Alcohols are polar compounds.They interact with themselves and with other polar compounds by dipole- dipole interactions. Dipole-dipole interaction:the attraction between the positive end of one dipole and the negative end of another. -Unusually high boiling points due to hydrogen bonding between molecules. -Small alcohols are miscible in water,but solubility decreases as the size of the alkyl group increases. 00a H H 0 1u=1.69D 0=1.30D u=0.08D CH,CH, HC CH H.C CH ethanol,MW 46 dimethyl ether,MW 46 propane,MW 44 bp78℃ bp-25C bp-42C
Physical Properties - + + O H H H C H ❖Alcohols are polar compounds. They interact with themselves and with other polar compounds by dipoledipole interactions. ❖Dipole-dipole interaction: the attraction between the positive end of one dipole and the negative end of another. ◼Unusually high boiling points due to hydrogen bonding between molecules. ◼Small alcohols are miscible in water, but solubility decreases as the size of the alkyl group increases
Physical Properties Hydrogen bonding:when the positive end of one dipole is an H bonded to F,O,or N (atoms of high electronegativity)and the other end is F,O, or N the strength of hydrogen bonding in water is approximately 21 kJ (5 kcal)/mol hydrogen bonds are considerably weaker than covalent bonds -nonetheless,they can have a significant effect on physical properties Alcohol ether Hydrogen bond H R hydrogen bond donor acceptor
Physical Properties ❖Hydrogen bonding: when the positive end of one dipole is an H bonded to F, O, or N (atoms of high electronegativity) and the other end is F, O, or N ◼the strength of hydrogen bonding in water is approximately 21 kJ (5 kcal)/mol ◼hydrogen bonds are considerably weaker than covalent bonds ◼nonetheless, they can have a significant effect on physical properties R O H H O O R R R O H H O R R O H H O R
hydrogen bonding Hydrogen fluoride In ice,each water molecule is held arrange in a zig-zag way by four hydrogen bonds in a in solid state.The tetrahedral configuration. hydrogen bond enthalpy is about 28 kJ/mol
Hydrogen fluoride arrange in a zig-zag way in solid state. The hydrogen bond enthalpy is about 28 kJ/mol
Biological importance of H-bon (a) δ+ =O11111H peptide chain (b) -peptide chain H6. N-peptide chain HO 0=C δ+
Biological importance of H-bond
Solubility in Water TABLE 10-3 Solubility of Alcohols in Water (at 25C) H Solubility Alcohol in Water CH3一CH2-CH2一CH2 hydrophilic region methyl miscible hydrophobic region ethyl miscible n-propyl miscible t-butyl miscible isobutyl 10.0% n-butyl 9.1% H H n-pentyl 2.7% cyclohexyl 3.6% Solubility decreases as the size n-hexyl 0.6% phenol 9.3% of the alkyl group increases. hexane-1,6-diol miscible Pearson Prentice Hall.Inc
Solubility in Water Solubility decreases as the size of the alkyl group increases
Physical Properties bp Solubility Structural Formula Name MW (癢) in Water CH3OH Methanol 32 65 Infinite CH3CH3 Ethane 30 -89 Insoluble CH3 CH2 OH Ethanol 46 78 Infinite CH3 CH2 CH3 Propane 44 42 Insoluble CH3 CH2CH2 OH 1-Propanol 60 97 Infinite CH3 CH2 CH2 CH3 Butane 58 0 Insoluble CH3(CH2)2 CH2OH 1-Butanol 74 117 8g/100g CH3(CH2)3 CH3 Pentane 72 36 Insoluble HOCH2(CH2)2CH2 OH 1,4-Butanediol 90 230 Infinite CH3(CH2)3CH2 OH 1-Pentanol 88 138 2.3g/100g CH3(CH2)4CH3 Hexane 86 69 Insoluble
Physical Properties Structural Formula Name bp (癈) Solubility in Water Methanol 32 65 Infinite Ethane 30 -89 Insoluble Ethanol 46 78 Infinite Propane 44 -42 Insoluble 1-Propanol 60 97 Infinite Butane 58 0 Insoluble 1-Pentanol 88 138 2.3 g/100 g 1,4-Butanediol 90 230 Infinite Hexane 86 69 Insoluble 1-Butanol 74 117 8 g/100 g Pentane 72 36 Insoluble CH3 CH2 CH2 OH CH3 CH2 CH2 CH3 CH3 OH CH3 CH3 CH3 CH2 OH CH3 CH2 CH3 CH3 ( CH2 ) 3 CH2 OH HOCH2 ( CH2 ) 2 CH2 OH CH3 ( CH2 ) 4 CH3 CH3 ( CH2 ) 2 CH2 OH CH3 ( CH2 ) 3 CH3 MW
Acidity of Alcohols pKa range:15.5-18.0 (water:15.7) Acidity decreases as alkyl group increases. Acidity decreases as the bulk of the alkyl group increases. Halogens increase the acidity. Phenol is 100 million times more acidic than cyclohexanol! TABLE 10-4 Acid-Dissociation Constants of Representative Alcohols Alcohol Structure Ka pKa methanol CH3-OH 3.2×10-16 15.5 ethanol CH3CH2-OH 1.3×1016 15.9 2-chloroethanol CI-CH2CH2-OH 5.0×1015 14.3 2.2.2-trichloroethanol Cl3C-CH2-OH 6.3×1013 12.2 isopropyl alcohol (CH3)2CH-OH 3.2×1017 16.5 t-butyl alcohol (CH3)3C-OH 1.0×10-18 18.0 cyclohexanol C6HI-OH 1.0×1018 18.0 phenol C6Hs-OH 1.0×1010 10.0 Comparison with Other Acids water H2O 1.8×10-16 15.7 acetic acid CH3COOH 1.6×105 4.8 hydrochloric acid HCI 1.6×10+2 -2.2 Copyright 2005 Pearson Prentice Hall.Inc
Acidity of Alcohols ❖pKa range: 15.5-18.0 (water: 15.7) ❖Acidity decreases as alkyl group increases. ❖Acidity decreases as the bulk of the alkyl group increases. ❖Halogens increase the acidity. ❖Phenol is 100 million times more acidic than cyclohexanol!