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CH3CH2CH2 Br C O CHE 242 H H Unit V Structure and Reactions of Alcohols, Ethers and Epoxides; Basic Principles of NMR Spectroscopy CHAPTER ELEVEN Terrence P. Sherlock Burlington County College 2004 H H CH3CH2CH2 Br 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 H C O H H H => 2 CH3CH2CH2 Br Summary Table Chapter 11 H C O H H H 3 => CH3CH2CH2 1º, 2º, 3º Carbons Br C O H H H => Chapter 11 H 4 CH3CH2CH2 Br Oxidation of 2° Alcohols • • • • C O H H H 2° alcohol becomes a ketone Reagent is Na2Cr2O7/H2SO4 Active reagent probably H2CrO4 Color change: orange to greenish-blue OH CH3CHCH2CH3 Na2Cr2O7 / H2SO4 O CH3CCH2CH3 => Chapter 11 H 5 CH3CH2CH2 Oxidation of 1° Alcohols Br C O H H H • 1° alcohol to aldehyde to carboxylic acid • Difficult to stop at aldehyde • Use pyridinium chlorochromate (PCC) to limit the oxidation. • PCC can also be used to oxidize 2° alcohols to ketones. OH N H CrO3Cl CH3CH2CH2CH2 O CH3CH2CH2CH => Chapter 11 H 6 CH3CH2CH2 3° Alcohols Don’t Oxidize Br C O H H H • Cannot lose 2 H’s • Basis for chromic acid test Chapter 11 => H 7 CH3CH2CH2 Br Alcohol as a Nucleophile H C C O H H H O R X • ROH is weak nucleophile • RO- is strong nucleophile • New O-C bond forms, O-H bond breaks. => Chapter 11 H 8 CH3CH2CH2 Alcohol as an Electrophile • OH- is not a good leaving group unless it is protonated, but most nucleophiles are strong bases which would remove H+. • Convert to tosylate (good leaving group) to react with strong nucleophile (base) Br C O H H H H + C O C-Nuc bond forms, C-O bond breaks => Chapter 11 H 9 CH3CH2CH2 Br Formation of Tosylate Ester H C O H H H H C O C C H O O Cl O S O N O CH3 S O CH3 p-toluenesulfonyl chloride TsCl, “tosyl chloride” Chapter 11 O S O CH3 ROTs, a tosylate ester => 10 CH3CH2CH2 Br SN2 Reactions of Tosylates • • • • • • C O H H H With hydroxide produces alcohol With cyanide produces nitrile With halide ion produces alkyl halide With alkoxide ion produces ether With ammonia produces amine salt With LiAlH4 produces alkane => Chapter 11 H 11 CH3CH2CH2 Summary of Tosylate Reactions Br C O H H H => Chapter 11 H 12 CH3CH2CH2 Reduction of Alcohols Br C O H H H • Dehydrate with conc. H2SO4, then add H2 • Tosylate, then reduce with LiAlH4 OH CH3CHCH3 H2SO4 alcohol OH CH3CHCH3 alcohol CH2 CHCH3 H2 Pt alkene TsCl CH3CH2CH3 alkane OTs CH3CHCH3 tosylate Chapter 11 LiAlH4 CH3CH2CH3 alkane H => 13 CH3CH2CH2 Reaction with HBr • • • • Br C O H H H -OH of alcohol is protonated -OH2+ is good leaving group 3° and 2° alcohols react with Br via SN1 1° alcohols react via SN2 R O H H3O + H R O H Chapter 11 - Br R Br H => 14 CH3CH2CH2 Mechanism with PBr3 Br C O H H H • P bonds to -OH as Br leaves • Br- attacks backside (S 2) N • HOPBr2 leaves Chapter 11 => H 15 Reaction with Thionyl Chloride • • • • CH3CH2CH2 Br C O H H H Produces alkyl chloride, SO2, HCl S bonds to -OH, Cl leaves Cl- abstracts H+ from OH C-O bond breaks as Cl transferred to C Chapter 11 H 16 => CH3CH2CH2 Periodic Cleavage of Glycols Br C O H H H Same products formed as from ozonolysis of the corresponding alkene. CH3 H CH3 C C CH3 OH OH HIO4 CH3 CH3 H C + O O C CH3 O3 (CH3)2S OsO4 H2O2 H C H3C C CH3 => CH3 Chapter 11 H 17 CH3CH2CH2 Br Fischer Esterification H C O H H H • Acid + Alcohol yields Ester + Water • Sulfuric acid is a catalyst. • Each step is reversible. O CH3 C OH CH3 + H O CH2CH2CHCH3 + H O CH3 CH3C OCH2CH2CHCH3 + HOH => Chapter 11 18 CH3CH2CH2 Br Tosylate Esters C O H H H • Alcohol + p-Toluenesulfonic acid, TsOH • Acid chloride is actually used, TsCl O CH3CH2 O H + HO S CH3 O O CH3CH2 O S O Chapter 11 H CH3 => + HOH 19 CH3CH2CH2 Br Sulfate Esters H C O H H H Alcohol + Sulfuric Acid O HO S O + OH H + H O CH2CH3 O S OCH2CH3 O O CH3CH2O H + HO HO S O + OCH2CH3 O Chapter 11 H CH3CH2O S OCH2CH3 O => 20 CH3CH2CH2 Br Nitrate Esters O O + N OH + H O CH2CH3 H O H C O H H H N OCH2CH3 O CH2 O H CH2 O H CH2 O H + 3 HO NO2 CH2 O NO2 CH2 O NO2 CH2 O NO2 nitroglycerine glycerine Chapter 11 21 => CH3CH2CH2 Br Phosphate Esters O HO P OH O OH CH3OH CH3O P OH CH3OH C O H H H O CH3O P OCH3 OH OH CH3OH O CH3O P OCH3 OCH3 Chapter 11 H => 22 CH3CH2CH2 Phosphate Esters in DNA O CH2 Br C O H H H base O H H H O O CH2 O H P O base O H H O O CH2 O H P O base O H H O O CH2 O H P O base O H H O O P O Chapter 11 O H => 23 CH3CH2CH2 Br Alkoxide Ions H C O H H H • ROH + Na (or NaH) yields sodium alkoxide • RO- + 1° alkyl halide yields ether (Williamson ether synthesis) CH3 CH3CH2CHCH3 + CH3CH2 Br O CH2CH2CH O CH2CH3 => Chapter 11 24 POWER POINT IMAGES FROM “ORGANIC CHEMISTRY, 5TH EDITION” L.G. WADE ALL MATERIALS USED WITH PERMISSION OF AUTHOR CH3CH2CH2 Br C O H H H PRESENTATION ADAPTED FOR BURLINGTON COUNTY COLLEGE ORGANIC CHEMISTRY COURSE BY: ANNALICIA POEHLER STEFANIE LAYMAN CALY MARTIN Chapter 11 H 25