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Organic Chemistry 2 > Aldehydes and Ketones (Chapter 17) > Flashcards

Aldehydes and Ketones (Chapter 17) Flashcards

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1
Q

Hybridizations within Aldehyde/Ketone

A
  • The carbon (C) is sp2-hybridized.
  • The oxygen (O) is sp2-hybridized.
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2
Q

Reagents: Jones Oxidation

A
  • NaCr2O7, H2SO4
  • CrO3, H2SO4, H2O
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3
Q

1° Alcohol → Aldehyde

A

PCC

Pyridinium Chlorochromate

Jones Oxidation of a 1° Alcohol yeilds a Carboxylic Acid.

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4
Q

2° Alcohol → Ketone

A
  • Jones Oxidation
  • PCC
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5
Q

1° Alkyl Benzene → Ketone

A

Jones Oxidation

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6
Q

Oxidation: PCC vs. Jones

A

Jones Oxidation requires an aqueous acid (i.e. H2O), whereas PCC involves a non-aqeuous acid.

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7
Q

Allylic Alcohol → Aldehyde/Ketone

A

Oxidation via MnO2

MnO2 is a mild oxidant (i.e. it cannot oxidize non-allylic alcohols or alkenes).

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8
Q

Product of Allylic Alcohol Oxidation

A
  • α,β-Unsaturated Aldehyde (if 1° Alcohol)
  • α,β-Unsaturated Ketone (if 2°/3° Alcohol)
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9
Q

Alkene → Aldehyde/Ketone

A

Ozonolysis

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10
Q

Reagents: Ozonolysis

A
  1. O3, CH2Cl2
  2. Zn, CH3COOH
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11
Q

Terminal Alkyne → Ketone

A

Hg(II)-Catalyzed Hydration

Oxymercurtion

Hg(II)-catalyzed hydration is a Markovnikov addition reaction.

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12
Q

Reagents: Hg(II)-Catalyzed Hydration

A

HgSO4, H2O, H2SO4

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13
Q

Hydration: Markovnikov vs. Anti-Markovnikov

A
  • Markovnikov: Alcohol (—OH) adds to the most substituted carbon.
  • Anti-Markovnikov: Alcohol (—OH) adds to the least substituted carbon.
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14
Q

Terminal Alkyne → Aldehyde

A

Hydroboration-Oxidation

Hydroboration-oxidation is an anti-Markovnikov addition reaction.

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15
Q

Reagents: Hydroboration-Oxidation

A
  1. BH3
  2. H2O2, NaOH
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16
Q

Benzene → Aldehyde/Ketone-Substituted Benzene

A

Friedel-Crafts Acylation

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17
Q

Reagents: Friedel-Crafts Acylation

A

Acyl Halide + Lewis Acid

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18
Q

Geminal Diol vs. Vicinal Diol

Gem-Diol vs. Vic-Diol

A
  • Geminal Diol: A compound containing two alcohol groups (—OH) are bonded to the same sp3-hybridized carbon atom.
  • Vicinal Diol: A compound containing two alcohol groups (—OH) are bonded to adjacent sp3-hybridized carbon atoms.
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19
Q

Aldehyde/Ketone → Geminal Diol

A

Hydration

The hydration of aldehydes/ketones can be acid-catalyzed OR base-catalyzed.

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20
Q

Geminal Diol → Aldehyde/Ketone

A

Dehydration

The hydration of aldehydes/ketones is reversible.

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21
Q

Why must the carbonyl Oxygen be protonated in acid-catalyzed nucleophilic addition?

Addition to Aldehydes/Ketones

A

The nucleophile present under acidic conditions is too weak to add to the carbonyl Carbon without prior protonation of the carbonyl Oxygen.

Protonation of the carbonyl Oxygen increases the partial-positive charge on the carbonyl Carbon, which allows the weak nucleophile to add to the Carbon.

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22
Q

Nucleophile: Hydration of Aldehyde/Ketone

A
  • Basic Conditions: OH–
  • Acidic Conditions: H2O
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23
Q

Work-Up Step: Hydration of Aldehyde/Ketone

A
  • Basic Conditions: Protonation via H2O
  • Acidic Conditions: Deprotonation via H2O
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24
Q

Equilibrium Preference of Aldehyde/Ketone Hydration

A
  • Hydration of ketones will favor the reagent (i.e. Ketone) over the product (i.e. 2° Gem-Diol)
  • Hydration of aldehydes will favor neither the reagent (i.e. Aldehyde) nor the product (1° Gem-Diol).
  • Hydration of formaldehyde will favor the product (i.e. Methanediol) over the reagent (i.e. Formaldehyde).
  • Hydration of acyl halides will favor the product (i.e. Halide Gem-Diol) over the reagent (i.e. Acyl Halide).

The alcoholic addition to aldehydes/ketones has an identical equilibrium preference trend.

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25
Q

Reactivity Trend of Carbonyl Groups

A

The more positively charged the carbonyl Carbon is, the more reactive it will be during nucleophilic addition.

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26
Q

Hemiacetal vs. Acetal

A
  • Hemiacetal: A compound containing an alcohol group (—OH) and an ether group (—OR) are bonded to the same sp3-hybridized carbon atom.
  • Acetal: A compound containing two ether groups (—OR) are bonded to the same sp3-hybridized carbon atom.
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27
Q

Aldehyde/Ketone → Hemiacetal/Acetal

A

Alcohol Addition

  • The addition of one equivalent of alcohol is required to synthesize the hemiacetal.
  • The addition of two equivalents of alcohol is required to synthesize the acetal.
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28
Q

Hemiacetal/Acetal → Aldehyde/Ketone

Alcoholic Addition to Aldehyde/Ketone is Reversible

A

Alcohol Cleavage

  • Hemiacetal: Alcohol cleavage can occur in acidic conditions OR basic conditions
  • Acetal: Alcohol cleavage can occur ONLY in acidic conditions.
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29
Q

Conditions of Alcohol Addition to Aldehydes/Ketones

A
  • Hemiacetal: Alcohol addition can occur in acidic conditions OR basic conditions
  • Acetal: Alcohol addition can occur ONLY in acidic conditions.
30
Q

Reagents: Hemiacetal Cyclization

Starting Material: Compound contantaining Aldehyde Group AND Alcohol Group

A
  • Acid-Catalyzed: H+, H2O
  • Base-Catalyzed: OH–, H2O
31
Q

Reagents: Acetal Cyclization

Starting Material: Compound contantaining Ketone Group AND Alcohol Group

A
  • Acid-Catalyzed: H+, H2O
  • Base-Catalyzed: OH–, H2O
32
Q

When is the ring-formation of cyclic hemiacetals/acetals favored?

A

Hemiacetal/Acetal cyclization reactions are thermodynamically favorable if the product is a five-membered ring or six-membered ring.

33
Q

Aldehyde/Ketone → Cyclic Acetal

A

Ethanediol Protection

The cyclic acetal is highly stable/unreactive under basic conditions.

34
Q

Reagents: Ethanediol Protection/Deprotection

A
  • Protection: 1,2-Ethanediol, H3O+
  • Deprotection: H3O+
35
Q

Cyclic Acetal → Aldehyde/Ketone

A

Ethanediol Deprotection

The 1,2-Ethanediol protection of aldehydes/ketones is reversible.

36
Q

Properties of Cyclic Acetals

A
  • Unreactive w/ Strong Nucleophiles
  • Highly Stable under Basic Conditions
  • Highly Unstable under Acidic Conditions

The Ethanediol deprotection of aldehydes/ketones occurs in acidic conditions ONLY.

37
Q

Cyclic Thioacetal → Aldehyde/Ketone

A

Ethanedithiol Deprotection

The 1,2-Ethanedithiol protection of aldehydes/ketones is reversible.

38
Q

Aldehyde/Ketone → Cyclic Thioacetal

A

Ethanedithiol Protection

The cyclic thioacetal is highly stable/unreactive under basic conditions and acidic conditions.

39
Q

Reagents: Ethanedithiol Protection/Deprotection

A
  • Protection: 1,2-Ethanedithiol, ZnCl2
  • Deprotection: HgCl2, H2O, CaCO3
40
Q

Aldehyde/Ketone → Methylene Group

Cyclic Thioacetal

A
  1. Ethanedithiol Protection
  2. Raney-Nickel Reduction
41
Q

Reagents: Raney-Nickel Reduction

A

Raney-Ni, H2

42
Q

Cyclic Thioacetal → Methylene Group

A

Raney-Nickel Reduction

43
Q

Imine

A

Any compound that contains a Carbon-Nitrogen double bond (C=N).

The nitrogen atom of the imine is sp2-hybridized. (This hybridization causes the C=N–R structure to be bent.)

44
Q

Enamine

A

A compound containing an alkenyl substituent attached to the Nitrogen atom.

The Carbon atom of the C—N is double-bonded to another Carbon (C=C).

45
Q

Aldehyde/Ketone → Imine

A

1° Amine Nucleophilic Addition

Ammonia Nucleophilic Addition

The 1° amine nucleophilic addition to aldehydes/ketones occurs in neutral conditions OR weakly acidic (i.e. pH = 4–5) conditions.

46
Q

Reagents: 1° Amine Elimination

A

H2O

The 1° amine nucleophilic elimination ONLY occurs in neutral conditions OR weakly acidic (i.e. pH = 4–5) conditions.

47
Q

Reagents: 1° Amine Nucleophilic Addition

A

R—NH2

NH3

The 1° amine can directly attack the carbonyl Carbon without protonation of the carbonyl Oxygen. (Primary amines are stronger nucleophiles that alcohols/water.)

48
Q

Imine → Aldehyde/Ketone

A

1° Amine Elimination

The 1° Amine nucleophilic addition to aldehydes/ketones is reversible.

49
Q

Why are amines stronger nucleophiles than alcohols?

A
  • The lone pair electrons on the Nitrogen atom (of the amine) are more donatable due to Nitrogen having a lower electronegativity than Oxygen.
  • The lone pair electrons on the Oxygen atom (of the alcohol) are less donatable due to Oxygen having a greater electronegativity than Nitrogen.
50
Q

Why is 1° Amine Nucleophilic Addition ineffective in strongly acidic conditions?

A

The 1° amine will become fully protonated (to yield NH4+/NH3R+) under acidic conditions; the NH4+/NH3R+ is not nucleophilic.

51
Q

Hemiaminal

A

A compound containing one alcohol group (—OH) and one amine group bonded to the same sp3-hybridized carbon atom.

52
Q

Iminium Ion

A

A compound that contains a Carbon-Nitrogen double bond (C=N) with a positive charge on the Nitrogen.

The iminium ion is an intermediate compound formed during the 1°/2° amine nucleophilic addition to an aldehyde/ketone.

53
Q

Oxocarbenium Ion

A

A compound containing an Oxygen-substituted carbonyl group with a positive charge on the Oxygen.

The oxocarbenium ion is an intermediate compound formed during acid-catalyzed reactions involving an aldehyde/ketone.

54
Q

Enol vs. Enolate

A
  • Enol: A compound containing an alcohol group bonded to a Carbon atom of an alkene (i.e. the alcohol group is adjacent to the alkene group).
  • Enol: A compound containing an oxide bonded to a Carbon atom of an alkene (i.e. the oxide is adjacent to the alkene group).

  • The π-bond electrons of the alkene are in conjugation with the Oxygen lone pair (of the alcohol/oxide).
  • The enol form and enolate form are tautomers of one another.
55
Q

Hydrazone

A

A compound containing a Carbon double-bonded to a Nitrogen (C=N) that is single-bonded to an amine group (—NH2)

R2—C=N—NH2

56
Q

Hydrazone → Methylene Group

A

Basic Decomposition of Hydrazone

57
Q

Aldehyde/Ketone → Hydrazone

A

Hydrazine Addition

58
Q

Reagents: Hydrazine Addition

A

H2N—NH2

59
Q

Reagents: Decomposition of Hydrazone

A

NaOH

60
Q

Aldehyde/Ketone → Methylene Group

Hydrazone

A
  1. Hydrazine Addition
  2. Decomposition of Hydrazone
61
Q

Aldehyde/Ketone → Enamine

A

2° Amine Nucleophilic Addition

62
Q

2° Amine Nucleophilic Addition

A

R2—NH

63
Q

Why is the 3° Amine Nucleophilic Addition to aldehydes/ketones impossible?

A

The tertiary amine does not contain a Hydrogen atom that can be transfered to the oxide ion (following attack of the amine).

64
Q

Cyanohydrin

A

A compound containing a cyanide group (—CN) and an alcohol group bonded to the same sp3-hybridized carbon atom.

65
Q

Aldehyde/Ketone → Cyanohydrin

A

Cyanide Nucleophilic Addition

The first step of the cyanide nucleophilic addition is reversible

66
Q

Reagents: Cyanide Nucleophilic Addition

A

NaCN, HCl

The HCl must be added slowly to avoid the generation of the toxic HCN compound.

67
Q

Aldehyde/Ketone → Alkene

A

Wittig Reaction

Nucleophilic Addition of Phosphorus Ylides

The Witting Reaction allows for the creation of a Carbon-Carbon double bond (C=C).

68
Q

Mechanism: Phosphorus Ylide Formation

A
  1. SN2 Attack of 1°/2° Alkyl Halide by P(Ph)3
  2. Deprotonation (from C—H bond) via Strong Base
69
Q

Why are Triphenylphoshine and Phosphorus Ylides good nucleophiles?

P(Ph)3 = Triphenylphosphine

A
  • P(Ph)3: The Phosphorus lone-pair electrons are highly donatable due to the low electronegativity of Phosphorus.
  • Phosphorus Ylide: The zwitterionic resonance structure places a negative charge on the Phosphorus-bonded Carbon atom.
70
Q

Reagents: Phosphorus Ylide Formation

P(Ph)3 = Starting Reagent

A
  1. 1°/2° Alkyl Halide
  2. Organolithium Compound
71
Q

Hydrazine

A

H2N—NH2

Organic Chemistry 2 (12 decks)

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