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Organic Chemistry Reviews Chapter 12

Organic Chemistry Reviews Chapter 12. Cindy Boulton February 22, 2009. Redox. Reduced: Gain electrons Oxidation: Loose electrons Organic Redox: Oxidation [O]: loss of Hydrogen and/or gain of Oxygen Reduction [H]: loss of Oxygen and/or gain of Hydrogen. Reduction by Hydride.

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Organic Chemistry Reviews Chapter 12

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  1. Organic Chemistry ReviewsChapter 12 Cindy Boulton February 22, 2009

  2. Redox • Reduced: Gain electrons • Oxidation: Loose electrons • Organic Redox: • Oxidation [O]: loss of Hydrogen and/or gain of Oxygen • Reduction [H]: loss of Oxygen and/or gain of Hydrogen

  3. Reduction by Hydride • Making Alcohols • Hard to reduce: Carboxcylic Acids and Esters • Use LiAlH4/H3O+ • Easy to reduce: Ketone and Aldehyde • Use NaBH4/H2O • Use LiAlH4/H3O+ • Mechanism: • Hydride attacks the partially positive Carbon and then partial negative Oxygen gains a Hydrogen

  4. Oxidation • Cr6+ Oxidizing reagents • Cr6+ -> Cr3+ • Primary or Secondary Alcohols are oxidized to a Ketone or Aldehyde • Aldehyde is oxidized to Carboxycylic acid • Forms a aldehyde hydrate, Gem-diol • Only in the presence of Aqueous Chromic Acid (water) • Aqueous Chromic Acid • HCrO3/H2O • NaCr2O7/H2SO4/H2O • CrO3/H2O/acetone • Organic Chromic Acid • CrClO3- • PCC/CH2Cl2

  5. Oxidation • KMnO4 Oxidation • Organic oxidaion • Mn+7 -> Mn+4 reduction • Primary Alcohol reacts with KMnO4/H2O/OH- to form carboxcylic acid • No aldehyde intermediate

  6. Organometallic Reagents • Carbon attached to a metal • Carbanion sources: Carbon is partial negative • Organolithium • C-Br + 2Li -> C-Li + LiBr • Carbon is reduced • Lithium is oxidized • Organomagnesium Bromide • Grignard Reagents • C-Br + Mg -> C-MgBr • Carbon is reduced • Magnesium is oxidized

  7. Organometallic Reagents • Carbanion acts as a base • Electron Pair Donor/Gains a Hydrogen • The more substituted the stronger the base • Alkyl groups act as electron density donors • Carbanion acts as a nucleophile • If the base is too strong than an elimination reaction is more likely • Carbon-Carbon bond is formed

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