Terrence P. Sherlock Burlington County College 2004

CHE 242Unit VStructure and Reactions of Alcohols, Ethers and Epoxides; Basic Principles of NMR SpectroscopyCHAPTER ELEVEN Terrence P. Sherlock Burlington County College 2004

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

1º, 2º, 3º Carbons => Chapter 11

=> Oxidation of 2° Alcohols • 2° alcohol becomes a ketone • Reagent is Na2Cr2O7/H2SO4 • Active reagent probably H2CrO4 • Color change: orange to greenish-blue Chapter 11

=> Oxidation of 1° Alcohols • 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. Chapter 11

=> 3° Alcohols Don’t Oxidize • Cannot lose 2 H’s • Basis for chromic acid test Chapter 11

Alcohol as a Nucleophile • ROH is weak nucleophile • RO- is strong nucleophile • New O-C bond forms, O-H bond breaks.=> Chapter 11

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)=>  + C-Nuc bond forms, C-O bond breaks Chapter 11

Formation of Tosylate Ester p-toluenesulfonyl chloride TsCl, “tosyl chloride” ROTs, a tosylate ester => Chapter 11

SN2 Reactions of Tosylates • 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

Summary of Tosylate Reactions => Chapter 11

=> Reduction of Alcohols • Dehydrate with conc. H2SO4, then add H2 • Tosylate, then reduce with LiAlH4 Chapter 11

=> Reaction with HBr • -OH of alcohol is protonated • -OH2+ is good leaving group • 3° and 2° alcohols react with Br- via SN1 • 1° alcohols react via SN2 Chapter 11

Mechanism with PBr3 • P bonds to -OH as Br- leaves • Br- attacks backside (SN2) • HOPBr2 leaves => Chapter 11

Reaction with Thionyl Chloride • 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

=> Periodic Cleavage of Glycols Same products formed as from ozonolysis of the corresponding alkene. Chapter 11

=> Fischer Esterification • Acid + Alcohol yields Ester + Water • Sulfuric acid is a catalyst. • Each step is reversible. Chapter 11

=> Tosylate Esters • Alcohol + p-Toluenesulfonic acid, TsOH • Acid chloride is actually used, TsCl Chapter 11

=> Sulfate Esters Alcohol + Sulfuric Acid Chapter 11

=> Nitrate Esters Chapter 11

=> Phosphate Esters Chapter 11

Phosphate Esters in DNA => Chapter 11

=> Alkoxide Ions • ROH + Na (or NaH) yields sodium alkoxide • RO- + 1° alkyl halide yields ether (Williamson ether synthesis) Chapter 11

POWER POINT IMAGES FROM “ORGANIC CHEMISTRY, 5TH EDITION”L.G. WADEALL MATERIALS USED WITH PERMISSION OF AUTHORPRESENTATION ADAPTED FOR BURLINGTON COUNTY COLLEGEORGANIC CHEMISTRY COURSEBY:ANNALICIA POEHLER STEFANIE LAYMAN CALY MARTIN Chapter 11

Terrence P. Sherlock Burlington County College 2004