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Chapter 12 Reactions of Alcohols, Ethers, Epoxides, and Sulfur-Containing Compounds

Chapter 12 Reactions of Alcohols, Ethers, Epoxides, and Sulfur-Containing Compounds Organometallic Compounds. Irene Lee Case Western Reserve University Cleveland, OH. Reactions of Alcohols. reaction with hydrogen halides acid-catalyzed dehydration (E 1 Rxn)

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Chapter 12 Reactions of Alcohols, Ethers, Epoxides, and Sulfur-Containing Compounds

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  1. Chapter 12 Reactions of Alcohols, Ethers, Epoxides, and Sulfur-Containing Compounds Organometallic Compounds Irene Lee Case Western Reserve University Cleveland, OH

  2. Reactions of Alcohols • reaction with hydrogen halides • acid-catalyzed dehydration (E1 Rxn) • reaction with thionyl chloride • reaction with phosphorous tribromide & PCl3 • conversion to sulfonate esters

  3. Secondary and tertiary alcohols undergo SN1 reactions with hydrogen halides

  4. Primary alcohols undergo SN2 reactions with hydrogen halides

  5. ZnCl2 can be used to catalyze certain SN2 reactions

  6. Rearrangement of secondary or tertiary alcohols can occur in the SN1 reaction

  7. Amines do not undergo substitution reactions because NH2– is a very strong base (a very poor leaving group) RCH2F > RCH2OH > RCH2NH2 HF H2O NH3 pKa= 15.7 pKa= 36 pKa= 3.2

  8. Other Methods for Converting Alcohols into Alkyl Halides

  9. Activation by SOCl2

  10. Converting Alcohols into Sulfonates (Excellent Leaving Groups)

  11. Several sulfonyl chlorides are available to react with -OH group

  12. SN2 Reactions of Activated Sulfonates

  13. Dehydration of Alcohols To prevent the rehydration of the alkene product, one needs to remove the product as it is formed

  14. Carbocation Rearrangement

  15. Ring Expansion

  16. Primary Alcohols Undergo Dehydration by an E2 Pathway

  17. Stereochemistry of the E1 Dehydration

  18. Milder Dehydration

  19. Substitution Reactions of Ethers Activation of ether by protonation

  20. Reactions of Epoxides Epoxides

  21. Nucleophilic attack of hydroxide ion on ethylene oxide and on diethyl ether

  22. Ring Opening

  23. When a nucleophile attacks an unprotonated epoxide, the reaction is a pure SN2 reaction

  24. Epoxides Are Synthetically Useful Reagents

  25. Crown Ethers

  26. A crown ether specifically binds certain metal ions or organic molecules to form a host–guest complex, an example of molecular recognition

  27. Thiols are sulfur analogs of alcohols ethanethiol 1-propanethiol 2-mercaptoethanol 3-methyl-1-butanethiol They are stronger acids (pKa= 10) than alcohols, but do not exhibit hydrogen-binding

  28. In protic solvent, thiolate ions are better nucleophiles than alkoxide ions CH3OH

  29. The sulfur analogs of ethers are called sulfides or thioethers Sulfur is an excellent nucleophile because its electron cloud is polarized

  30. Organometallic Compounds An organic compound containing a carbon–metal bond

  31. Preparation of Organolithium Compounds hexane 1-bromobutane butyllithium hexane phenyllithium chlorobenzene

  32. Preparation of Organomagnesium Compounds

  33. Alkyl halides, vinyl halides, and aryl halides can all be used to form organolithium and organomagnesium compounds However, these organometallic compounds cannot be prepared from compounds containing acidic groups (OH, NH2, NHR, SH, C=CH, CO2H)

  34. Coupling Reactions Formation of carbon–carbon bonds

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