Organic Chem Test 4

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Organic Chem Test 4
2011-04-21 11:24:31
Carbonyl compounds II III

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  1. Hydrolysis of an Ester
    forms a carboxylic acid and an alcohol

    Catalyzed by an acid
  2. Transesterification
    turns one ester into another, a type of alcoholysis

    ester + alcohol

    catalyzed by an acid
  3. aminolysis
    Not catalyzed by an acid, it will protonate the amine

    forms another amine

    ester + amine
  4. Ester + Cl-
    No reaction

    Leaving Group on ester (RO-) is a stroner base than Cl-
  5. Acyl chloride + alcohol
    Forms an ester
  6. Acyl Chloride + H2O
    forms an alcohol
  7. Acyl Chloride + 2amine
    forms an amide

    requires twice the amine as chloride because the HCl formed will protonate the amine, making it unable to react
  8. Relative Reactivities of Caboxylic Acid Derivatives
    • Acyl Chloride > Ester ~ Corboxylic Acid > amide
    • LG: (Cl-) (RO-) (HO-) (-NH2)
  9. Steps in Nucleophilic Acyl Subsitution Reaction
    • 1.) Tetrahedral Intermediate is formed.
    • B/C C=O bond is polar
    • 2.) Tetrahedral Intermediate collapses.
    • Expels the group that is the weakest base
  10. Best Leaving Groups
    • Weak bases.
    • Characteristics:
    • More stable than strong bases
    • More electronegative than strong bases
    • -Electron withdrawling (adds to polarity)
    • Form weaker bonds than strong bases
  11. Relative Boiling Points of Carboxylic Acid Derivatives
    Amide > Carboxylic Acid >> Ester ~ Acyl Chloride ~ aldehyde ~ Ketone

    • Amides --> strong dipole interactions (resonance)
    • Carboxylic Acid --> forms 2 hydrogen bonds
  12. Carboxylic Acid Derivative + 1. stronger base
    2. weaker base
    3. similar base

    (Compared to leaving group)
    1. Forms a new carboxylic acid derivative

    2. No reaction

    3. After reaction both reatant and product present
  13. Carbonyl Carbon
    The carbon double bonded to an oxygen in the acyl group
  14. Acyl Chloride + 1. nuetral nucleophile

    Important Steps
    1. Formation of a tetrahedral intermediate (slow)

    2. Proton dissociation (equilibrium)

    3. Weaker base is expelled and intermediate collapses
  15. Acyl Chloride + 2. Negatively Charged Nucleophile

    Important Steps
    1. Nucleophile attacks carbonyl carbon, forming tetrahedral intermediate

    2. Intermediate collapses, expelling the weaker base
  16. Mechanism:

    Acid Catalyzed Hydrolysis of Ester
    • 1. Acid protonates the carbonyl oxygen
    • 2. Nucleophile attacks the carbony carbon
    • - Forms a protonated Tetrahedral Intermediate I
    • 3. Proton dissociation
    • - Forms T.I. II
    • 4. 2 possible protonation sites for H+
    • - Forms T.I I or III (weak base is protonated)
    • 5. Weaker base is expelled
  17. Acid Protonation Selectivity
    Acids will protonate the atom in the compound with the highest electron density, the most basic atom
  18. Relative Reactivities toward nucleophilic acyl substition
    Carboxylic Acids
    Leaving Group

    OH > NH2 > O-

    In acidic form has approximately same reactivity as an ester
  19. Carboxylic Acid + Alcohol
    • Forms an Ester
    • Must be carried out in acidic solution
    • - Catalyzes reaction
    • - Keeps Carboxylic acid in acid form

    Mechanism is exact opposite of acid catalyzed hydrolysis of an Ester
  20. Carboxylic Acid + Amine
    No nucleophilic acyl substitution reaction

    • Carboxylic acid is and Acid, amine is a base
    • - Acid will protonate amine immediately
  21. Nucleophilic substitution reactions of epoxides under acidic conditions
    Under acidic conditions, the nucleophile attacks the more substituted ring-carbon
  22. Nucleophilic substitution reactions of epoxides under basic conditions
    Under basic conditions, the nucleophile attacks the less sterically hindered (or least substituted) ring carbon
  23. Acid-catalyzed amide hydrolysis
    • 1. Acid protonates the carbonyl oxygen
    • 2. Nucleophile attacks the carbony carbon
    • - Forms a protonated Tetrahedral Intermediate I
    • 3. Proton dissociation - Forms T.I. II
    • 4. 2 possible protonation sites for H+
    • - Forms T.I I or III
    • 5. Weaker base is expelled
  24. Carboxylic Acid ---> acyl chloride
    • reagent: SOCl2 Thionyl Chloride
    • Heat required to activate
  25. Nitriles
    • Contain a C=N functional group
    • Considered carboxylic acid derivatives
    • - react with H2O to form carboxylic acids
    • Less Reactive than Amides
  26. Naming Nitriles
    Add "nitrile" to parent alkane name

    ex: ethanenitrile
  27. Nitrile + H2O
    Catalyst - Acid and Heat

    --> carboxylic acid
  28. Preparation of a Nitrile
    Sn2 reaction of akyl Halide and cyanide ion (-C=N)
  29. Reduction of an alkyne to an alkane
    Reagent: H2

    catalyst: Pt/C or Pd/C

    works for nitriles also
  30. Activation of Carboxylic Acids
    Reagent SOCl2

    Add Heat

    Forms an Acyl Chloride
  31. Class II Carbonyl Compounds
    Do not have a group that can be replaced by a nucleophile.

    • Aldehydes and Ketones
    • - Leaving group (H- and R-) are too basic
  32. Aldehydes
    The carbonyl carbon is bonded to a hydrogen and to an alkyl or aryl group

    Special case: Formaldehyde - carbonyl carbon is bonded to two hydrogens
  33. Ketone
    The carbonyl carbon is bonded to two alkyl or aryl groups.
  34. Acetone
    carbonyl carbon is bonded to two methyl groups

    • common name for smallest Ketone
    • - Propanone
    • Widely used as solvent
  35. Naming Aldehydes
    Replace the "e" on the name of the parent hydrocarbon with "al"

    Position of Carbonyl group is not desiginated, it is always on the end and always has the 1 position

    Ex: Methanal, Ethanal
  36. Naming Ketones
    Replace the "e" in the parent hydrocarbon with "one"

    The Chain is numbered in the direction that gives the carbonyl carbon the smaller number

    No number needed for cyclic ketones
  37. Relative Reactivities of class II carbonyl compounds
    Formaldehyde > aldehyde > ketone

    • 1. The Hydrogens in aldehydes are electron withdrawling when compared to alkyl groups
    • 2. Less steric interaction in aldehydes (H group)
  38. Relative Reactivities of Ketones
    ketones with smaller alkyl groups bonded to the carbonyl carbon are more reactive than ketones with large alkyl groups
  39. Relative Reactivities of Carbonyl Compounds (class I and II)
    Acyl Chloride > Aldehyde > Ketone > Ester > Carboxylic Acid > Amide > Carboxylate Ion
  40. Class II carbonyl compound reaction with nucleophile
    Leaving group is too basic to be expelled

    Undergo nucleophilic addition reactions
  41. Grignard Reagents
    The most widely used carbon nucleophiles

    • Prepared by adding an alkyl halide to Mg shavings being stirred in diethyl either
    • -Reaction insterts Mg between the C and halogen
    • -React as if they were carbanions
  42. Gignard Reagents as Nucleophiles
    • Mg is less electronegative than C
    • -The carbon bonded to Mg has a negative charge

    Such a strong base that it reacts immediately with any acid (even traces amounts of poor acids) in solution
  43. Aryl Group
    refers to any functional group or substituent derived from a simple aromatic ring
  44. Mechanism: Aldehyde/ketone with grignard reagent
    • 1. Nucleophilic attack by Grignard Reagent on carbonyl carbon
    • -Forms an Alkoxide ion complexed with Mg+
    • 2. Reaction with H3O+
    • -Protonation of the alkoxide ion forms an alcohol
  45. Product of the Reaction of Grignard Reagent with Formaldehyde
    Product is a primary alcohol
  46. Product of the Reaction of Grignard Reagent with Aldehyde other than Formaldehyde
    The procuct is a secondary alcohol
  47. Product of a grignard reagent reacting with a ketone
    The product is a tertiary alcohol
  48. Reactions of an ester or acyl chloride with the Grignard reagent (overview)
    • Undergo two successive reactions
    • 1. nucleophilic acyl substitution reaction
    • an ester has a group that can be replaced
    • - sp3 carbon attached to O and another E- atom
    • 2. nucleophilic addition reaction
    • The ketone formed in 1. reacts with 2R-MgBR and H3O+

    Forms alcohol
  49. Product of the reaction of Acyl chloride or ester with two equivalents of grignard reagents
    forms a tertiary alcohol, with two identical groups

    • 1st equivalent replaces Cl in a nucleophilic acyl substituion reaction
    • 2nd equivalent reacts in a nucleophilic addition reaction
  50. Reaction of Aldehydes and ketones with Hydride ion
    Nucleophilic addition reaction (addition of H = reduction)

    • 1.NaBH4 is the source of the hydride ion
    • - H- attaches to carbonyl carbon forming an alkoxide ion
    • 2.H3O+ is added after 1.
    • - protonates carbonyl oxygen
  51. Reaction of Class 1 carbonyl compounds with hydride ion
    • Undergoes two succesive reactions
    • 1. Nucleophilic acyl substitution (with H-)
    • 2. Nucleophilic addition reaction (with 2nd equivalent of H-)

    Source of hydride ion: NaBH4 (if more reactive than a ketone) or LiAlH4 (if less reactive than a ketone)
  52. Product of an Ester reacting with LiAlH4
    • 1. 2 successive reactions with H- (from LiAlH4)
    • 2. H3O+

    Produces two alcohols, one corresponding with the acyl portion of the ester and one corresponding the alkyl portion
  53. Procuct of the reaction of carboxylic acid with LiAlH4
    • 1. 2 successive reactions with H- (from LiAlH4)
    • 2. H3O+

    forms a single primary alcohol
  54. Reaction of Amide with Hydride ion
    • 1. 2 successive reactions with H- (from LiAlH4)
    • 2. H2O
    • - the product is an amine

    • if H3O+ is used instead of h20 in 2.
    • -the acid would protonate the amine
    • - the product would be an ammonium ion
  55. Imine (Hybridization and orbitals)
    a compound with a carbon - nitrogen double bond

    • Imine Nitrogen is sp2 hybridized
    • 1 sp2 orbital - sigma bond with Imine carbon
    • 1 sp2 orbital - sigma bond with a substituent
    • last sp2 orbital contains a lone pair
    • P orbital overlaps with imine carbon's p orbital
  56. Product of the reaction of an aldehyde or ketone with a primary amine
    • Product is an imine
    • - requires trace amounts of acid
  57. Product of the reaction of an aldehyde or ketone with a secondary amine
    • product is an enamine
    • - requires trace amounts of acid
  58. Enamine
    • a tertiary amine with a double bond in the alpha, beta - position relative the nitrogen atom
    • C=C--N (two R groups attached to N)
  59. Mechanism of Imine formation
    • 1. The amine attacks the cabonyle carbon
    • 2. the alkoxide ion is protonated
    • 3. the Ammonium ion loses a Hydrogen by dissociation
    • - forms a nuetral tetrahedral intermediate (a carbinolamine)
    • 4. either nitrogen or oxygen can be protonated
    • 5. elimination of H2O from the oxygen protonated intermediate forms a protonated imine
    • 6. dissociation forms an imine
  60. acid-cataylzed hydrolysis of an imine
    forms a carbonyl compound and a primary amine
  61. Acid catalyzed hydrolysis of an enamine
    forms a carbonyl compound (ketone of aldehyde) and a secondary amine
  62. Reaction of a ketone or aldehyde with secondary amine
    • forms an enamine
    • - requires trace amounts of acid
  63. a Hydrate
    a molecule with OH groups on the same carbon
  64. Procuct of the addition of water to a ketone or aldehyde
    forms a hydrate in presence of acid catalyst
  65. Mechanism for Acid-catalyzed hydrate formation
    • 1. the acid protonates the carbonyl oxygen, makes the carbonyl carbon more succeptible to nucleophilic attack
    • 2. water attacks the carbonyl cation
    • 3. loss of a proton from the protonated tetrahedral intermediate
    • -produces a hydrate
  66. How substituents on carbonyl carbon affect the extent to which a ketone or aldehyde is hydrated
    • 0.2% of acetone hydrated at equilibrium
    • 99.9% of formaldehyde is hydrate at equilibrium

    Bulky substituents and electron donating substituents decrease the percentage of hydrate present at equilibrium

    small substuents increase it
  67. Product of one equivalent of alcohol and an aldehyde
    Product of two equivalents of acohol and an aldehyde
    a hemiacetal

    an acetal

    (both require acid catalyst b/c alcohols are poor nucleophiles)
  68. ketones react with aldehydes to form
    1. hemiketals

    • second equivalent of alcohol
    • 2. ketals
  69. Mechanism for acid-catalyzed ketal and acetal formation
    • 1. acid protonates the carbonyl oxygen
    • 2. nucleophile attacks the carbonyl oxygen
    • 3. proton dissociation
    • - forms hemi - ketal or hemiacetal
    • 4. either the OH or the OR' of the hemiketal/acetal group can be protonated
    • 5. Loss of H2O from tetrahedral intermediate with protonated OH
    • 6. nucleophile attacks the carbonyl carbon
    • 7. proton dissociation

    forms a ketal or acetal
  70. Nucleophilic addition to unsaturated carbonyl compounds
    (alpha carbon double bonded to beta carbon and sigma bonded to carbonyl carbon)
    • 1,2 addition or direct addition
    • oxygen (1) gets the hydrogen
    • carbonyl carbon (2) gets the nucleophile
    • 1,4 addition or conjugate addition
    • beta carbon (4) gets nucleophile
    • oxygen (1) gets the hydrogen
    • - Forms an enol which tautomerizes into a ketone
  71. Conjugate products are favored
    by nucleophiles that are weak bases.
  72. Direct addition products are favored
    By strong bases

    ex: ethly alcohol in Grignard reagent
  73. Oxidation of primary alcohol
    [aldehyde] ---> a carboxylic acid

    Reagent is H2CrO4
  74. Oxidation of secondary alcohol
    forms a ketone

    H2CrO4 is reagent
  75. Primary alcohol and PCC
    solvent (CH2Cl2)

    stops the oxidation at the aldehyde intermediate
  76. Dehydration Reaction of Alcohol
    H2SO4 and Heat

    forms alkene and water

    tertiary > secondary > primary