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Boiling Points

=>. Boiling Points. Solubility decreases as the size of the alkyl group increases . =>. Solubility in Water. Methanol. “Wood alcohol” Industrial production from synthesis gas Common industrial solvent Fuel at Indianapolis 500

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Boiling Points

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  1. => Boiling Points

  2. Solubility decreases as the size of the alkyl group increases. => Solubility in Water

  3. Methanol • “Wood alcohol” • Industrial production from synthesis gas • Common industrial solvent • Fuel at Indianapolis 500 • Fire can be extinguished with water • High octane rating • Low emissions • But, lower energy content • Invisible flame =>

  4. Ethanol • Fermentation of sugar and starches in grains • 12-15% alcohol, then yeast cells die. • Distillation produces “hard” liquors • Azeotrope: 95% ethanol, constant boiling • Denatured alcohol used as solvent • Gasahol: 10% ethanol in gasoline • Toxic dose: 200 mL ethanol, 100 mL methanol =>

  5. => 2-Propanol • “Rubbing alcohol” • Catalytic hydration of propene

  6. Acidity of Alcohols • pKa range: 15.5-18.0 (water: 15.7) • Acidity decreases as alkyl group increases. • Halogens increase the acidity. • Phenol is 100 million times more acidic than cyclohexanol! =>

  7. Table of Ka Values =>

  8. => Formation of Alkoxide Ions React methanol and ethanol with sodium metal (redox reaction). React less acidic alcohols with more reactive potassium.

  9. Formation of Phenoxide Ion Phenol reacts with hydroxide ions to form phenoxide ions - no redox is necessary. O O H O H + + H O H p K = 1 5 . 7 a p K = 1 0 a =>

  10. Synthesis (Review) • Nucleophilic substitution of OH- on alkyl halide • Hydration of alkenes • water in acid solution (not very effective) • oxymercuration - demercuration • hydroboration - oxidation =>

  11. Glycols (Review) • Syn hydroxylation of alkenes • osmium tetroxide, hydrogen peroxide • cold, dilute, basic potassium permanganate • Anti hydroxylation of alkenes • peroxyacids, hydrolysis =>

  12. Organometallic Reagents • Carbon is bonded to a metal (Mg or Li). • Carbon is nucleophilic (partially negative). • It will attack a partially positive carbon. • C - X • C = O • A new carbon-carbon bond forms. =>

  13. Grignard Reagents • Formula R-Mg-X (reacts like R:-+MgX) • Stabilized by anhydrous ether • Iodides most reactive • May be formed from any halide • primary • secondary • tertiary • vinyl • aryl =>

  14. => Some Grignard Reagents

  15. Organolithium Reagents • Formula R-Li (reacts like R:-+Li) • Can be produced from alkyl, vinyl, or aryl halides, just like Grignard reagents. • Ether not necessary, wide variety of solvents can be used. =>

  16. => Reaction with Carbonyl • R:- attacks the partially positive carbon in the carbonyl. • The intermediate is an alkoxide ion. • Addition of water or dilute acid protonates the alkoxide to produce an alcohol.

  17. => Synthesis of 1° Alcohols Grignard + formaldehyde yields a primary alcohol with one additional carbon.

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