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Capítulo 10 Estructura y Síntesis de Alcoholes

Organic Chemistry , 6 th Edition L. G. Wade, Jr. Capítulo 10 Estructura y Síntesis de Alcoholes. Jo Blackburn Richland College, Dallas, TX Dallas County Community College District ã 2006, Prentice Hall. Estructura de Alcoholes. Grupo Funcional : (-OH) Hidroxilo

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Capítulo 10 Estructura y Síntesis de Alcoholes

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  1. Organic Chemistry, 6th EditionL. G. Wade, Jr. Capítulo 10Estructura y Síntesis de Alcoholes Jo Blackburn Richland College, Dallas, TX Dallas County Community College District ã 2006,Prentice Hall

  2. Estructura de Alcoholes • GrupoFuncional: (-OH) Hidroxilo • Oxígenoessp3 => Chapter 10

  3. Clasificación • 1rio.: C enlazado al –OH estáenlazadosólo a otro C. • 2rio.: C enlazado al –OH estáenlazadosólo a dos C. • 3rio.: C enlazado al –OH estáenlazadosólo a tres C. • Aromáticos (fenoles): -OH estáenlazado a un anillo de benceno.=> Chapter 10

  4. => Clasifique Chapter 10

  5. Nomenclatura IUPAC • Cadena más larga con el grupo -OH. • Substituir terminación –ano del alcano por -ol. • Enumerar la cadena por el extremo más cercano al -OH. => Chapter 10

  6. Ejemplos 2-metil-1-propanol 2-butanol 3-bromo-3-metilciclohexanol => 2-metil-2-propanol Chapter 10

  7. Alcoholes insaturados • Grupo –OH toma precedencia. • Use el nombre del alqueno o alquino. 4-penten-2-ol => Chapter 10

  8. Acidos Esters Aldehídos Cetonas Alcoholes Aminas Alquenos Alquinos Alcanos Eteres Haluros => Prioridades en el Nombre Acido 4-hidroxibutanoico Chapter 10

  9. Nombres comunes isobutil alcohol sec-butil alcohol => Chapter 10

  10. Dioles hexano-1,6- diol => Chapter 10

  11. Glicoles • 1, 2 dioles (dioles vecinales) se llaman glicoles. etano-1,2- diol propano-1,2- diol propylen glycol => etilen glycol Chapter 10

  12. Fenoles 4-metilfenol 3-clorofenol => Chapter 10

  13. Propiedades Físicas • Normalmente tienen altos P.Eb. Por los Puentes de H. • Alcoholes pequeños son solubles en agua,pero la solubilidad disminuye al aumentar el tamaño del grupo alquílico. => Chapter 10

  14. => Puntos de Ebullición Chapter 10

  15. Solubilidad disminuye al aumentar tamaño del grupo alquílico. => Solubilidad en Agua Chapter 10

  16. Metanol • “Alcohol de madera” • Industrialmente se obtiene del gas natural • Industrialmente se usa como solvente Etanol • Fermentación de azucar y almidón en granos • Bebidas Chapter 10

  17. => 2-Propanol “Rubbing alcohol” Chapter 10

  18. Acidez de Alcoholes • pKa : 15.5-18.0 (H2O: 15.7) • La Acidezdisminuye a medidaqueaumenta el grupoalquílico. • Los Halógenosaumentan la acidez. • Fenoles100 millionesde vecesmásácidoqueciclohexanol! => Chapter 10

  19. TablaValores de Ka => Chapter 10

  20. => Formación de IonesAlcóxidos Alcoholes menos reactivos se tratan con K (más reactivo). Chapter 10

  21. Formación de Ion Fenóxido O O H O H + + H O H p K = 1 5 . 7 a p K = 1 0.0 a => Chapter 10

  22. Síntesis • Substitución Nucleofílica de Haluros de Alquilo. • Hidratación de Alquenos • H2O en medio ácido • hidroboración => Chapter 10

  23. Glicoles • Syn hidroxilación de alquenos • osmium tetroxide, hydrogen peroxide • cold, dilute, basic potassium permanganate • Anti hydroxylation of alkenes • peroxyacids, hydrolysis => Chapter 10

  24. 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. => Chapter 10

  25. 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 => Chapter 10

  26. => Some Grignard Reagents Chapter 10

  27. 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. => Chapter 10

  28. => 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. Chapter 10

  29. => Synthesis of 1° Alcohols Grignard + formaldehyde yields a primary alcohol with one additional carbon. Chapter 10

  30. => Synthesis of 2º Alcohols Grignard + aldehyde yields a secondary alcohol. Chapter 10

  31. => Synthesis of 3º Alcohols Grignard + ketone yields a tertiary alcohol. Chapter 10

  32. => How would you synthesize… Chapter 10

  33. Grignard Reactions with Acid Chlorides and Esters • Use two moles of Grignard reagent. • The product is a tertiary alcohol with two identical alkyl groups. • Reaction with one mole of Grignard reagent produces a ketone intermediate, which reacts with the second mole of Grignard reagent. => Chapter 10

  34. Grignard + Acid Chloride (1) • Grignard attacks the carbonyl. • Chloride ion leaves. Ketone intermediate => Chapter 10

  35. Grignard and Ester (1) • Grignard attacks the carbonyl. • Alkoxide ion leaves! ? ! Ketone intermediate => Chapter 10

  36. => Second step of reaction • Second mole of Grignard reacts with the ketone intermediate to form an alkoxide ion. • Alkoxide ion is protonated with dilute acid. Chapter 10

  37. => How would you synthesize... Using an acid chloride or ester. Chapter 10

  38. => Grignard Reagent + Ethylene Oxide • Epoxides are unusually reactive ethers. • Product is a 1º alcohol with 2 additional carbons. Chapter 10

  39. Limitations of Grignard • No water or other acidic protons like O-H, N-H, S-H, or -C—C-H. Grignard reagent is destroyed, becomes an alkane. • No other electrophilic multiple bonds, like C=N, CN, S=O, or N=O. => Chapter 10

  40. Reduction of Carbonyl • Reduction of aldehyde yields 1º alcohol. • Reduction of ketone yields 2º alcohol. • Reagents: • Sodium borohydride, NaBH4 • Lithium aluminum hydride, LiAlH4 • Raney nickel => Chapter 10

  41. => Sodium Borohydride • Hydride ion, H-, attacks the carbonyl carbon, forming an alkoxide ion. • Then the alkoxide ion is protonated by dilute acid. • Only reacts with carbonyl of aldehyde or ketone, not with carbonyls of esters or carboxylic acids. Chapter 10

  42. => Lithium Aluminum Hydride • Stronger reducing agent than sodium borohydride, but dangerous to work with. • Converts esters and acids to 1º alcohols. Chapter 10

  43. Comparison of Reducing Agents • LiAlH4 is stronger. • LiAlH4 reduces more stable compounds which are resistant to reduction. => Chapter 10

  44. => Catalytic Hydrogenation • Add H2 with Raney nickel catalyst. • Also reduces any C=C bonds. Chapter 10

  45. Thiols (Mercaptans) • Sulfur analogues of alcohols, -SH. • Named by adding -thiol to alkane name. • The -SH group is called mercapto. • Complex with heavy metals: Hg, As, Au. • More acidic than alcohols, react with NaOH to form thiolate ion. • Stinks! => Chapter 10

  46. => Thiol Synthesis Use a large excess of sodium hydrosulfide with unhindered alkyl halide to prevent dialkylation to R-S-R. Chapter 10

  47. => Thiol Oxidation • Easily oxidized to disulfides, an important feature of protein structure. • Vigorous oxidation with KMnO4, HNO3, or NaOCl produces sulfonic acids. Chapter 10

  48. End of Chapter 10 Chapter 10

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