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Organic Chemistry Reviews Chapter 11. Cindy Boulton February 8, 2009. Alcohol vs Ethers. Alcohol CH 3 OH IUPAC: methanol Radiofuntional name: methyl alchol Ether CH 3 OCH 3 IUPAC: methoxymethane Radiofunctional name: dimethyl ether. Alcohol Chemistry and Properties.

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organic chemistry reviews chapter 11

Organic Chemistry ReviewsChapter 11

Cindy Boulton

February 8, 2009

alcohol vs ethers
Alcohol vs Ethers
  • Alcohol
    • CH3OH
    • IUPAC: methanol
    • Radiofuntional name: methyl alchol
  • Ether
    • CH3OCH3
    • IUPAC: methoxymethane
    • Radiofunctional name: dimethyl ether
alcohol chemistry and properties
Alcohol Chemistry and Properties
  • Determined by –OH group
  • -OH is a polar covalent bond
  • Cable of hydrogen bond
  • Raises boiling point
  • Strong dipole
  • Hydrogen has a pKa = 17
    • Readily removed by a strong base
  • Dissolves polar and ionic compounds
ether chemistry and properties
Ether Chemistry and Properties
  • Oxygen has a partial negative charge
  • Two Carbons attached have a partial positive charge
  • Charges partially cancelled each other out
  • Not as polar or reactive
  • Used as a solvent
    • Inert: not as reactive
synthesis of alcohols
Synthesis of Alcohols
  • Hydration of alkenes
    • By aqueous Sulfuric Acid (H+)
    • Regiochemistry: Markovinkov, incoming hydrogen goes to carbon with more hydrogen’s and forms a stable carbon cation
    • Stereochemistry: Racemic, an equal amount of new stereocenters (R and S) are formed
    • Pros:
      • Sulfuric Acid is cheap
      • Eliminate multiple steps (easy)
    • Cons:
      • Primary R-OH is difficult to make
      • Skeletal rearrangement is possible, carbocation will rearrange to a higher order
synthesis of alcohols1
Synthesis of Alcohols
  • Oxymercuration/Demercuration
    • Alkene reacts with 1) Hg(OAc)2 2) NaBH4, OH-
    • Hg has multiple bonds and partial bonds with carbocation
    • Blocks alkanide migration/skeletal rearrangement
    • Regiochemistry: Markovinkov
    • Stereochemistry: Racemic
    • Pros:
      • Skeletal rearrangement is blocked
    • Cons:
      • Hg is toxic and expensive
      • 2 Steps and multiple clean up steps
      • Lower overall yield
      • Primary Alcohols not likely formed
synthesis of alcohols2
Synthesis of Alcohols
  • Hydroboration-oxidation
    • Alkene reacts with 1) BH3 2) H2O2, OH-
    • Tranistion State: Boron and Hydrogen bonds to both Carbons, forms a trialkylborane
    • Regiochemistry: Antimarkovinkov-incoming Hydrogen goes to Carbon with less Hydrogen, Sterics
    • Stereochemistry: Racemic, Syn addition
    • Pros:
      • Can make Primary Alcohol
      • No Skeletal rearrangement
    • Cons:
      • 2 Steps
      • Costly
      • Needs clean up
sulfonates
Sulfonates
  • Good leaving group for SN1, SN2, E1, and E2 reactions
    • Stable ions and unreactive
    • Resonance Structure
    • Strong inductive effect
  • Alcohol is a bad leaving group but is changed to a have a sulfonate
  • Triflate (Tf): best
  • Tosylate (Tf)
  • Mesylate : worst
conversion of alcohols to alkyl halides
Conversion of Alcohols to Alkyl Halides
  • Alcohol is a poor leaving group, but a halide is a good leaving group for another reaction
  • Conversion by HX (X = Cl, Br, I), PBr3, and SOCl2
  • 1o Alcohol Mechanism
    • “SN2”- retains stereochemistry, no carbocation intermediate
  • 3o Alcohol Mechanism
    • “SN1”- sterics from the –R groups block SN2 reaction
    • A stable carbocation intermediate is fromed
    • Product is a racemic mixture with Optical Rotation = 0o
  • 2o Alcohol Mechanism
    • Either “SN1” or “SN2” depending on the –R groups
    • Identified by optical rotation