CH3CH2CH2 Organic Chemistry,7th Edition HH L.G.Wade,Jr. Chapter 11 Reactions of Alcohols Copyright 2010 Pearson Education,Inc
Chapter 11 Reactions of Alcohols Copyright © 2010 Pearson Education, Inc. Organic Chemistry, 7th Edition L. G. Wade, Jr. CH3CH2CH2 C H H Br O H H
Types of Alcohol Reactions Dehydration to alkene Oxidation to aldehyde,ketone Substitution to form alkyl halide ·Reduction to alkane ·Esterification ·Tosylation Williamson synthesis of ether Chapter 11 2
Chapter 11 2 Types of Alcohol Reactions • Dehydration to alkene • Oxidation to aldehyde, ketone • Substitution to form alkyl halide • Reduction to alkane • Esterification • Tosylation • Williamson synthesis of ether
Summary Table TABLE 11-1 Types of Reactions of Alcohols R-OH type of reaction Product dehydration R一OH alkenes R-OH esterification R-OCR esters oxidation R-OH ketones,aldehydes, acids tosylation R-OH R-OTs substitution R-OH R-X tosylate esters halides (good leaving group) reduction (1)form alkoxide R-OH R-H R-OH R-O-R' alkanes (2)RX ethers Copyright 2010 Pearson Prentice Hall,Inc. Chapter 11 3
Chapter 11 3 Summary Table
Oxidation States Easy for inorganic salts: CrO42-reduced to Cr2O3. -KMnO4 reduced to MnO2. .Oxidation:Gain of O,O2,or X2;loss of H2. Reduction:Gain of H2 (or H);loss of O or O2; and loss of X2. The gain or loss of H+,H2O,HX,etc.is neither an oxidation nor a reduction. Chapter 11 4
Chapter 11 4 Oxidation States • Easy for inorganic salts: ▪ CrO4 2- reduced to Cr2O3 . ▪ KMnO4 reduced to MnO2 . • Oxidation: Gain of O, O2 , or X2 ; loss of H2 . • Reduction: Gain of H2 (or H- ); loss of O or O2 ; and loss of X2 . • The gain or loss of H+ , H2O, HX, etc. is neither an oxidation nor a reduction
Oxidation States of Carbons OXIDATION H OH 0 R-C-H IO,R-C-H,R-C-H,R-C-OH +H0 aldehyde no bonds to H 0 R-C-R'10L,R-C-R'1O R-C-R'(0o furtber oxidntion) H +H,O alkane secondary alcohol ketone no bonds to O one bond toO two honds toO H OH R一C-R'IoLR一C一R'ualyno fher oxidation) R“ R" alkane tertiary alcohol no bonds to O one bond to O REDUCTION Copyright 2010 Pearson Prentice Hall.Inc Chapter 11 5
Chapter 11 5 Oxidation States of Carbons
Oxidation of 2 Alcohols 。2° alcohol becomes a ketone. OH NazCr2O/H,SO R-CH-R' R -R ·Oxidizing agent is secondary alcohol ketone Na2Cr207/H2S04: Example H ·Active reagent NazCr2O7 OH H,S04 probably is H2CrO4. cyclohexanol cyclohexanone (90%) ·Color change is orange to greenish- blue. Chapter 11 6
Chapter 11 6 Oxidation of 2° Alcohols • 2° alcohol becomes a ketone. • Oxidizing agent is Na2Cr2O7 /H2SO4 . • Active reagent probably is H2CrO4 . • Color change is orange to greenishblue
Oxidation Mechanism Formation of the chromate ester R一CO一H H-O-Cr-OH R OH H 0 alcohol chromic acid chromate ester Elimination of the chromate ester and oxidation of the carbinol carbon R R R OH R-C ' H2O:H .0. H.O 0 Cr(VI) Cr(IV) Copyright2010 Pearson Prentice Hall,Inc. Chapter 11 7
Chapter 11 7 Oxidation Mechanism
Oxidation of 1 Alcohols to Carboxylic Acids CH,OH C一OH NaCr2O7 H2SO4 cyclohexyl methanol cyclohexanecarboxylic acid (92%) Chromic acid reagent oxidizes primary alcohols to carboxylic acids. The oxidizing agent is too strong to stop at the aldehyde. Chapter 11 8
Chapter 11 8 Oxidation of 1° Alcohols to Carboxylic Acids • Chromic acid reagent oxidizes primary alcohols to carboxylic acids. • The oxidizing agent is too strong to stop at the aldehyde
Pyridinium Chlorochromate (PCC) Pyridinium chlorochromate (PCC). CrO,C1 CrO3'pyridine·HCI or pyH+CrOCI- Copyright010Pearson Prne Hall Inc PCC is a complex of chromium trioxide, pyridine,and HCI. Oxidizes primary alcohols to aldehydes. Oxidizes secondary alcohols to ketones. Chapter 11 9
Chapter 11 9 Pyridinium Chlorochromate (PCC) • PCC is a complex of chromium trioxide, pyridine, and HCl. • Oxidizes primary alcohols to aldehydes. • Oxidizes secondary alcohols to ketones
Pyridinium Chlorochromate (PCC) OH CrO3'pyridine-HCI(PCC) R一C一H R- 一H CH2Cl2 H primary alcohol aldehyde Example 0 PCC CH3(CH2)s-CH2OH CH2C12 CH3(CH2)5-C一H 1-heptanol heptanal(78%) Copyright2010 Pearson Prentice Hall,Inc. Chapter 11 10
Chapter 11 10 Pyridinium Chlorochromate (PCC)