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ALDEHYDES AND KETONES

ALDEHYDES AND KETONES. STRUCTURE. Aldehyde. Ketone. NOMENCLATURE. IUPAC Nomenclature of Ketones. Choose the longest continuous carbon chain that contains the carbonyl carbon Number from the end of the chain closest to the carbonyl carbon Ketone ending is -one.

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ALDEHYDES AND KETONES

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  1. ALDEHYDES AND KETONES

  2. STRUCTURE Aldehyde Ketone

  3. NOMENCLATURE

  4. IUPAC Nomenclature of Ketones • Choose the longest continuous carbon chain that contains the carbonyl carbon • Number from the end of the chain closest to the carbonyl carbon • Ketone ending is -one Do the ketonessection of Organic Nomenclature program!

  5. EXAMPLES 2-Pentanone 4-Ethyl-3-hexanone

  6. 3-Isopropylcyclopentanone

  7. KETONES Common, or Trivial, Names • Name each group attached to the carbonyl group as an alkyl group • Combine into a name, according to the pattern: alkyl alkyl’ ketone NOTE: This is not all one word!

  8. Example of Common Names Methyl propyl ketone Diethyl ketone

  9. benzophenone acetone acetophenone SPECIAL CASES diphenyl ketone dimethyl ketone A common laboratory solvent and cleaning agent methyl phenyl ketone KNOW THESE

  10. IUPAC Nomenclature of Aldehydes • Choose the longest continuous carbon chain that contains the carbonyl carbon • Number from the end of the chain closest to the carbonyl carbon (carbon #1!) • Aldehyde ending is -al Do the aldehydessection of Organic Nomenclature program.

  11. EXAMPLES aldehyde group is always carbon 1 pentanal 3 1 4 2 2-chloro-3-methylbutanal

  12. RECOGNIZE THESE Common Names of the Aldehydes

  13. formaldehyde benzaldehyde acetaldehyde SPECIAL CASES KNOW THESE

  14. Forming Common Names of Aldehydes USE OF GREEK LETTERS ……. w is always the end of the chain, no matter how long a-chlorocaproaldehyde w-chlorocaproaldehyde ( a-chlorohexanal ) ( w-chlorohexanal )

  15. REACTIVITY OF THE C=O GROUP NUCLEOPHILIC ADDITION

  16. .. .. - d- : : : d+ + GENERALIZED CHEMISTRY THE CARBONYL GROUP nucleophilic at oxygen H+ or E+ electrophiles add here nucleophiles attack here Nu: electrophilic at carbon

  17. NUCLEOPHILIC ADDITION TO C=O MECHANISMS IN ACID AND IN BASE

  18. Nucleophilic Addition to Carbonyl Basic or Neutral Solution an alkoxide ion - or on adding acid Good nucleophiles and strong bases (usually charged) BASIC SOLUTION

  19. Nucleophilic Addition to Carbonyl Acid Catalyzed more reactive to addition than the un- protonated precursor (+) Acid catalysis speeds the rate of addition of weak nucleophiles and weak bases (usually uncharged). ACIDIC SOLUTION stronger acid protonates the nucleophile pH 5-6

  20. CYANOHYDRINS

  21. Addition of Cyanide :C N: Buffered to pH 6-8 a cyanohydrin In acid solution there would be little CN-, and HCN (g) would be a problem (poison). A cyanohydrin

  22. CYANIDE ION BONDS TO HEMOGLOBIN .. Cyanide bonds (irreversibly) to the site (Fe II) where oxygen usually bonds. CYANIDE IS IS A POISON .. You die of suffocation - lack of oxygen. HCN is a gas that you can easily breathe into your lungs.

  23. ORGANOMETALLICS

  24. These reagents cannot exist in acid solution Synthesis of Alcohols Addition of Organometallic Reagents ether (R-Li) :R - workup step alcohol

  25. Summary of Reactions of Organometallics with Carbonyl Compounds • Organometallics with ketones yield tertiary alcohols • Organometallics with aldehydes yield secondary alcohols • Organometallics with formaldehyde yield primary alcohols. • Organometallics with carbon dioxide yield carboxylic acids. All review to you etc.

  26. HYDRATES

  27. Addition of Water aldehyde or ketone favored hydrates are unstable and cannot be isolated in most cases most hydrates revert to an aldehyde or ketone as soon as they form

  28. ACID CATALYSIS RECALL + .. .. .. + : : : + Acid catalysis enhances the reactivity of the carbonyl group - nucleophilic addition proceeds more easily. :Nu weak nucleophiles can react Water is a weak nucleophile.

  29. for most compounds the equilibrium favors the starting materials and you cannot isolate the hydrate In a reaction where all steps are reversible, the steps in the reverse reaction are the same as those in the forward reaction, reversed! WATER ADDS TO THE CARBONYL GROUP OF ALDEHYDES AND KETONES TO FORM HYDRATES catalyzed by a trace of acid + .. .. .. .. + : : : : : + a hydrate .. .. .. .. .. .. + .. MICROREVERSIBILITY:

  30. ISOTOPE EXCHANGE REVEALS THE PRESENCE OF THE HYDRATE 18 an excess of H2O18 shifts the equilibrium to the right 18 H+ + excess -H2O +H2O18 18 exchange shows the presence of a symmetric intermediate

  31. SOME STABLE HYDRATES these also indicate that hydrates are possible d- d+ d- chloral hydrate chloral d- 120o expected 60o required 109o expected 60o required sp2 sp3 cyclopropanone cyclopropanone hydrate

  32. SOME ADDITIONAL STABLE HYDRATES glyoxal phenylglyoxal

  33. ACETALS AND HEMIACETALS

  34. ACID CATALYSIS RECALL + .. .. .. + : : : + Acid catalysis enhances the reactivity of the carbonyl group - nucleophilic addition proceeds more easily. :Nu weak nucleophiles can react Alcohols are weak nucleophiles.

  35. Addition of Alcohols TWO MOLES OF ALCOHOL WILL ADD addition of one mole H+ hemiketal addition of second mole H+ an aketal The equilibria normally favor the aldehyde or ketone starting material, but we will show how they can be made.

  36. ACETALS AND HEMIACETALS aldehyde hemiacetal acetal ketone (hemiketal)* (ketal)* *older term *older term

  37. .. + Like a hydronium ion + + .. .. .. + : : : + .. .. .. .. ACID CATALYZED FORMATION OF A HEMIACETAL : first addition .. : Normally the starting material is favored - but a second molecule of alcohol can react if in excess (next slide) + + .. : .. hemiacetal

  38. FORMATION OF THE ACETAL ( from the hemiacetal ) remove + .. .. .. second addition .. .. : .. : + + : SN1 + : : : : .. .. hemiacetal Resonance stabilized carbocation .. .. .. : : + + : : : .. .. acetal

  39. STABILITY OF ACETALS AND HEMIACETALS Most hemiacetals are not stable, except for those of sugars (see later). Acetals are not stable in aqueous acid, but they are stable to aqueous base. H2SO4 AQUEOUS ACID + H2O AQUEOUS BASE NaOH no reaction H2O

  40. ADDITION OF WATER AND ALCOHOLS WATER H2O hydrate ALCOHOLS R-O-H R-O-H H2O hemiacetal acetal acetals are stable to base but not to aqueous acid H+ H2O H2O no reaction NaOH

  41. REAKSI OKSIDASI

  42. OKSIDASI ALDEHID DAN KETON • Keton tidak mudah dioksidasi • Aldehid sangat mudah dioksidasi, menjadi asam karboksilat Zat pengoksidasi : KMnO4, H, H2O

  43. Reaksi Reduksi

  44. Reaksi Reduksi • Reduksi aldehid menghasilkan alkohol primer • Reduksi keton menghasilkan alkohol sekunder • Zat pereduksi: H2, katalis Zn/Hg, HCl

  45. Reaksi Adisi-eliminasi

  46. Reaksi Adisi-eliminasi • Aldehid + Amina Primer Imina • Aldehid + Amina sekunder Enamina • Aldehid + Amina tersier hidrazon

  47. Ramalkan produk hemiasetal atau hemiasetal siklik dari: • 5-hidroksi-2-heksanon dengan air • 1,3,4,5,6-pentahidroksi-2-heksanon dengan air • propanal dengan metanol • Aseton dengan 1,2,3-propanatriol

  48. Ramalkan apa produk reaksi sikloheksanon dengan : • CH3NH2 • (CH3)2NH

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