tailieunhanh - Lecture Organic chemistry: Chapter 11 - L. G. Wade, Jr.

Chapter 11 - Reactions of Alcohols. Alcohols are important organic compounds because the hydroxyl group is easily converted to almost any other functional group. In Chapter 10, we studied reactions that form alcohols. In this chapter, we seek to understand how alcohols react and which reagents are best for converting them to other kinds of compounds. | Chapter 11 Reactions of Alcohols ©2010, Prentice Hall Organic Chemistry, 7th Edition L. G. Wade, Jr. Chapter 11 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 Summary Table Chapter 11 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 Oxidation States of Carbons Chapter 11 Oxidation of 2° Alcohols 2° alcohol becomes a ketone. Oxidizing agent is Na2Cr2O7/H2SO4. Active reagent probably is H2CrO4. Color change is orange to greenish-blue. Chapter 11 Oxidation Mechanism Chapter 11 Oxidation of 1° Alcohols to Carboxylic Acids Chromic acid reagent . | Chapter 11 Reactions of Alcohols ©2010, Prentice Hall Organic Chemistry, 7th Edition L. G. Wade, Jr. Chapter 11 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 Summary Table Chapter 11 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 Oxidation States of Carbons Chapter 11 Oxidation of 2° Alcohols 2° alcohol becomes a ketone. Oxidizing agent is Na2Cr2O7/H2SO4. Active reagent probably is H2CrO4. Color change is orange to greenish-blue. Chapter 11 Oxidation Mechanism Chapter 11 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. Chapter 11 Pyridinium Chlorochromate (PCC) PCC is a complex of chromium trioxide, pyridine, and HCl. Oxidizes primary alcohols to aldehydes. Oxidizes secondary alcohols to ketones. Chapter 11 Pyridinium Chlorochromate (PCC) Chapter 11 3° Alcohols Cannot Be Oxidized Carbon does not have hydrogen, so oxidation is difficult and involves the breakage of a C—C bond. Chromic acid test is for primary and secondary alcohols because tertiary alcohols do not react. Chapter 11 Other Oxidation Reagents CuO, 300°C (industrial dehydrogenation) Collins reagent: Cr2O3 in pyridine Jones reagent: chromic acid in acetone KMnO4 (strong oxidizer) Nitric acid (strong oxidizer) Swern oxidation: dimethylsulfoxide, with oxalyl chloride and hindered base, oxidizes 2 alcohols to ketones and 1 alcohols to aldehydes. Chapter 11 Suggest the most appropriate method for each