西北农林科技大学：《有机化学 Organic chemistry》课程PPT教学课件（2014）Chapter 14 & 15 Alcohols

有机化学oRcAn1©©ⅫEMISTRY 主：王德儒870928290) 理学院寇化素理科接2层26 Organic Chemistry,6th Edition L.G.Wade,Jr. Chapter 14 I15 Alcohols Key Notes Hydrogen bonding;Acidity;Lucas reagent; Dehydration;Williamson synthesis Homework: 14-29;14-30:e,g,h,Ij,l,m:14-32:b,c:14-37:b(P495) 15-27:c;15-28;15-37:a,c,e(P529):

Chapter 14 & 15 Alcohols Organic Chemistry, 6th Edition L. G. Wade, Jr. Key Notes Hydrogen bonding; Acidity; Lucas reagent ; Dehydration ; Williamson synthesis 有机化学ORGANIC CHEMISTRY 主讲：王俊儒 87092829(O) 理学院应化系理科楼2层C206 Homework: 14-29；14-30: e,g,h,I,j,l,m；14-32: b,c；14-37: b(P495)； 15-27: c；15-28；15-37: a,c,e (P529);

CONTENTS Structure Properties of Alcohols Preparation of alcohols Functional group transformation ■C-C bond formation Reduction of Carbonyl Rxns 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 ❖Rxns 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 1.4 0.96A H 104.5° H 108.9° water water water H H 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;SP3 hybridized;O:不等性SP杂化 2、-O-H,C-O为极性共价键 3、-OH,-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. 00 H H 0 1u=1.69D 0=1.30D u=0.08D H 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 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

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 ydrogen bond 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-bond (a) δ+ peptide chain (b) -peptide chain H6. N-peptide chain HO ● 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CH2一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 Prentice Hall,Inc

Solubility in Water Solubility decreases as the size of the alkyl group increases

Acidity of Alcohols pKa range:15.5-18.0 (water:15.7) decreases as alkyl group increases. 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 C1-CH2CH2一OH 5.0×1015 14.3 2.2,2-trichloroethanol Cl3C-CH2-OH 6.3×1013 12.2 isopropyl alcohol (CH3)2CH-OH 3.2×10-17 16.5 t-butyl alcohol (CH3)3C-OH 1.0×1018 18.0 cyclohexanol C6H11一OH 1.0×1018 18.0 phenol C6H5-OH 1.0×1010 10.0 Comparison with Other Acids water H2O 1.8×10-16 15.7 acetic acid CH COOH 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) ❖decreases as alkyl group increases. ❖decreases as the bulk of the alkyl group increases. ❖Halogens increase the acidity. ❖Phenol is 100 million times more acidic than cyclohexanol!

Acidity of Alcohols Structural Compound Formula pKa Hydrogen chloride HCI Stronger acid Acetic acid CH3 COOH 4.8 Methanol CH3OH 15.5 Water H2O 15.7 Ethanol CH3 CH2OH 15.9 2-Propanol (CH3)2CHOH Weaker 2-Me thyl-2-propanol (CH3)3COH 18 acid *Also given for comparis on are pK a values for water, acetic acid,and hydrogen chloride

Acidity of Alcohols ( CH3 ) 3 COH ( CH3 ) 2 CHOH CH3 CH2 OH H2 O CH3 OH CH3 COOH Hydrogen chloride HCl Acetic acid Methanol Water Ethanol 2-Propanol 2-Methyl-2-propanol Structural Formula Stronger acid Weaker acid *Also given for comparison are pK a values for water, acetic acid, and hydrogen chloride. Compound pKa -7 15.5 15.7 15.9 17 18 4.8