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CHAPTER 12

CHAPTER 12. 12.1 Nomenclature of Alcohols 12.2 Nomenclature of Ethers. learn on your own. 12.4 Conversion of Alcohols to Alkyl Halides. lecture. review : read on your own. Tosylates Review Section 10.3 pp 916-917 and 12.3 (end) just before Section 12.4. + lecture.

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CHAPTER 12

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  1. CHAPTER 12 12.1 Nomenclature of Alcohols 12.2 Nomenclature of Ethers learn on your own 12.4 Conversion of Alcohols to Alkyl Halides lecture review : read on your own Tosylates Review Section 10.3 pp 916-917 and 12.3 (end) just before Section 12.4 + lecture 12.7 Synthesis of Ethers read on your own not much new here (some lecture) 12.8 Epoxides 12.14 Synthesis of Alkynes using Acetylide Ions lecture 12.15 Synthesis of Nitriles using Cyanide Ion review

  2. WILLIAMSON ETHER SYNTHESIS

  3. WILLIAMSON ETHER SYNTHESIS alkyl halide - - .. .. .. .. : : : : R O + R’ X R O R’ + X .. .. .. .. alkoxide This is an SN2 method. The substrate must be primary or secondary. THIS IS THE BASIC WILLIAMSON METHOD Making the reactants from alcohols : .. .. - Na + : R O Na + H2 R O H ALKOXIDE: .. .. .. .. ALKYL HALIDE: : R’ O H R X ( X = Cl, Br, I ) .. .. various methods

  4. The method shown is better than : - .. + : .. WHY ? SAMPLE WILLIAMSON SYNTHESIS ethyl alcohol - .. : + .. primary ethyl isopropyl ether isopropyl alcohol

  5. MAKING ETHERS BY SOLVOLYSIS

  6. MAKING ETHERS BY SOLVOLYSIS If one of the alkyl groups in the target ether is tertiary, solvolysis may be the best method for synthesis. EtOH + SN1 Can this ether be made by the Williamson method? Yes, there are two SN2 possibilities. One works.

  7. SN2 WHICH ONE WORKS ? - + + new bond tertiary - + + primary new bond

  8. SN1 WHICH ONE WORKS ? solvolysis + new bond + new bond

  9. SYNTHESES USING ACETYLENE

  10. The reactions are carried out in liquid ammonia at -33o C ( b.p. of NH3 ). SODIUM AMIDE IS A STRONG BASE Strong enough to remove H from terminal ( end of chain ) acetylenes ammonia - .. .. - NaNH2 : : NH3 (liq) pKa ~ 25 an “acetylide” ion a good SN2 nucleophile A new carbon-carbon bond is formed FORMATION OF A NEW BOND - NH3 (liq) : CH3 Na+

  11. Fe3+ (catalyst) .. - + sodium amide : + H2 (g) strong base can remove H from alkynes FORMATION OF SODIUM AMIDE strong reducing agent solvated electron - . . + -33oC + n NH3(liq) NH3(g) dry ice / isopropyl alcohol - 78o C

  12. MAKING NEW C-C BONDS ACETYLIDE IONS

  13. USING ACETYLIDES TO MAKE NEW C-C BONDS STEP ONE SN2 reaction NaNH2 NH3(liq) - : STEP TWO NaNH2 (do it again) NH3(liq) - : could be a longer chain, 1o or 2o substrates (SN2) only

  14. HOW COULD YOU MAKE THESE COMPOUNDS ? 1) 5) 6) 2) 7) 3) 8) 4) Do in class.

  15. H2 can addto other double and triple bonds, not just C=C syn addition SOME OTHER APPLICATIONS OF CATALYTIC HYDROGENATION RANEY NICKEL .. .. H2 : : Ni, 2 atm 2 H2 : : = Ni, 2 atm Notice that the hydrogen gas is under pressure (2 atm) and that nickel ( Ni ) is used for the catalyst. These bonds are moredifficult to hydrogenate than C=C. The Ni catalyst is in a special form called “Raney Nickel”.

  16. HOW ABOUT THIS ? from

  17. MAKING NITRILES AND AMINES

  18. MAKING NITRILES AND AMINES - : : SN1 conc HCl SN2 forms benzyl carbocation NaCN acetone H2 : Ni amine nitrile Conc. HCl can be used here since stereochemistry does not matter - the molecule is not chiral. Otherwise, you would use SOCl2 in pyridine or ether depending on the desired stereochemical result.

  19. EPOXIDES

  20. EPOXIDES Here is an interesting intramolecular SN2 reaction. Intermolecular = between (two or more) molecules. Intramolecular = within the same molecule. Br2 a bromohydrin H2O .. - NaHCO3 : O-CO2H .. .. : weak base : : intramolecular SN2 reaction : : .. an “epoxide”

  21. OPENING EPOXIDE RINGS - 1 ACIDIC CONDITIONS The epoxide ring is rather strained, and is easily opened in either acidic conditions (SN1) or strongly basic conditions (SN2) or with good nucleophiles. 3-6 M H2SO4 opens to give best carbocation .. + : : : : 3o + adds to either side : : .. .. : : ACID OPENING + : .. .. SN1 a 1,2-diol

  22. OPENING EPOXIDE RINGS - 2 STRONG BASE (OH-, OR-) 3-6 M NaOH .. - : : .. - : .. attacks least hindered C BASE OPENING SN2 a 1,2-diol (“glycol”)

  23. OPENING EPOXIDE RINGS - 3 GOOD NUCLEOPHILES .. - : : - .. : : attacks least hindered C NUCLEOPHILE OPENING .. SN2

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