ORGANIC CHEMISTRY Chapter 12 12.4 Oxidation of alcohols Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 12 12.4 Oxidation of Alcohols
ORGANIC CHEMISTRY Chapter 12 12.4A Oxidation of Primary Alcohols to Aldehyd y des RCHOH RCHO o Primary alcohols can be oxidized to aldehydes and carboxylic acids [O] RCH2OH—RCHO—RCO2H 1 Alcohol Aldehyde Carboxylic acid o Aldehydes are more easily oxidized than primar alcohoIs Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 12 12.4A Oxidation of Primary Alcohols to Aldehydes RCH2OH RCHO Primary alcohols can be oxidized to aldehydes and carboxylic acids. RCH2OH RCHO RCO2H [O] [O] 1°Alcohol Aldehyde Carboxylic acid Aldehydes are more easily oxidized than primary alcohols
ORGANIC CHEMISTRY Chapter 12 o An excellent reagent for oxidation of primary alcohols to aldehydes is pyridinium chlorochromate(PCC) CH2OH PCC CHO CHoCI PCC (Pyridinium chlorochromate) CrO3 Hcl N一H CrOr Cl ridin PCC Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 12 An excellent reagent for oxidation of primary alcohols to aldehydes is pyridinium chlorochromate (PCC). CH2OH CHO 82% CH2Cl2 PCC PCC (Pyridinium chlorochromate) CrO3 + HCl + N N H pyridin CrO3Cl PCC
ORGANIC CHEMISTRY Chapter 12 12. 4B Oxidation of Primary alcohols to Carboxylic Acids RCHOH RCOH o Primary alcohols can be oxidized to carboxylic acids y potassium permanganate OH R-CH2OH+ KMnOA H2O,△ RCO2 K+ MnO2 H3O RCO2H Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 12 12.4B Oxidation of Primary Alcohols to Carboxylic Acids RCH2OH RCO2H Primary alcohols can be oxidized to carboxylic acids by potassium permanganate. R CH2OH + KMnO4 OH H2O, RCO2 K + MnO2 H3O RCO2H
ORGANIC CHEMISTRY Chapter 12 12. 4C Oxidation of Secondary alcohols to Ketones OH R-CH-R R-C-R o Secondary alcohols can be oxidized to ketones OH [O] R-CH-R R-C-R 2° Alcohol Ketone 9 Oxidizing agent o H, CrO4(crO3/h,sO4, Na, cr,o, H,SO4) o CrO3/H2SO4, H2O-acetone- Jones'reagent °KMnO Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 12 12.4C Oxidation of Secondary Alcohols to Ketones R CH R' OH R C R' O Secondary alcohols can be oxidized to ketones. R CH R' OH R C R' O [O] 2°Alcohol Ketone Oxidizing agent: H2CrO4 (CrO3 /H2SO4 ,Na2Cr2O7/ H2SO4) CrO3/ H2SO4 , H2O-acetone — Jones’ reagent KMnO4
ORGANIC CHEMISTRY Chapter 12 Na,Cr,O OH O HoSO Cyclohexanol Cyclohexanone (85%) o Jones oxidation OH O Cro3. hso HO, acetone Cyclooctane Cyclooctanone (92~96%) Na2Cr2O7/H2so R-CHDOH RCOH or Jones reagent Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 12 OH O H2SO4 Na2Cr2O7 Cyclohexanol Cyclohexanone (85%) Jones oxidation OH O CrO3, H2SO4 H2O,acetone (92 ~ 96%) Cyclooctanol Cyclooctanone R CH2OH RCO2H Na2Cr2O7/H2SO4 or Jones' reagent
ORGANIC CHEMISTRY Chapter 12 12. 4DA Mechanism of chromate Oxidations Step R O-H +HO→Cr-0 R HO OH O R H Hro-h H R、x0 O—Cr=0 HO COH2 OH R H R H Chromate ester Step 2 R Cr=o R O OH C-O+Cr-o+H-o-H R H R OH H Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 12 12.4D A Mechanism of Chromate Oxidations C O R' R H H HO Cr O O O + H O H H C O R' R H H HO Cr O O OH C O R' R H HO Cr O O OH2 C O R' R H OH Cr O O Chromate ester C O R' R H OH Cr O O H O H C O R' R + OH Cr O O H O H H + Step 1 Step 1 Step 2 Step 2
ORGANIC CHEMISTRY Chapter 12 o In aqueous solutions, the aldehyde initially formed reacts with water to formed an aldehyde hydrate which can then react with HCrOa to form a chromate ester and this can be oxidized to the carboxylic acid R R O r O-H HCrO4 H H H 0-HH O-H O HH R O-H R O-H t hcro t ho H0-Cr-OH O :O- O H Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 12 In aqueous solutions, the aldehyde initially formed reacts with water to formed an aldehyde hydrate which can then react with HCrO4- to form a chromate ester, and this can be oxidized to the carboxylic acid. C O H R H O H C O H R O H H C O H R O H H HCrO4 H C O H R O Cr H O O OH H O H C R O O H + HCrO3 + H3O
ORGANIC CHEMISTRY Chapter 12 12.4E A Chemical Test for Primary and Secondary alcohols o Primary and secondary alcohols are rapidly oxidized by a solution of crO3/H2SO4 R-CHOOH CrO 3+ OH Cr and oxidation products HSOA-HoO R-CH-R Clear orange solution Greenish opaque solution Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 12 12.4E A Chemical Test for Primary and Secondary Alcohols Primary and secondary alcohols are rapidly oxidized by a solution of CrO3 /H2SO4. R CH R' OH R CH2OH CrO3 H2SO4-H2O Cr and oxidation products 3+ Clear orange solution Greenish opaque solution
ORGANIC CHEMISTRY Chapter 12 12. 4f Spectroscopic Evidence for Alcohols IR:OH3200~3600cm o H NMR: CH-OH 3.3 4.0 ppm; 0.5-6 ppm,D,O exchange Q 3C NMR: C-OH 50-90 ppm OH Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 12 12.4F Spectroscopic Evidence for Alcohols IR: O—H 3200 ~ 3600 cm-1 1H NMR: CH—OH 3.3 ~ 4.0 ppm; 0.5 ~ 6 ppm, D2O exchange 13C NMR: C —OH 50 ~ 90 ppm OH
