Aldehydes and Ketones (Chapter 17) Flashcards

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
Reactivity Trend of Carbonyl Groups
## Footnote The *more positively charged* the carbonyl Carbon is, the *more reactive* it will be during nucleophilic addition.[](http://)
26
Hemiacetal vs. Acetal
* **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.
27
Aldehyde/Ketone → Hemiacetal/Acetal
Alcohol Addition ## Footnote * 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*.
28
Hemiacetal/Acetal → Aldehyde/Ketone | Alcoholic Addition to Aldehyde/Ketone is Reversible
Alcohol Cleavage ## Footnote * **Hemiacetal:** Alcohol cleavage can occur in *acidic* conditions OR *basic* conditions * **Acetal:** Alcohol cleavage can occur ONLY in *acidic* conditions.
29
Conditions of Alcohol Addition to Aldehydes/Ketones
* **Hemiacetal:** Alcohol addition can occur in *acidic* conditions OR *basic* conditions * **Acetal:** Alcohol addition can occur ONLY in *acidic* conditions.
30
*Reagents:* Hemiacetal Cyclization ## Footnote **Starting Material:** Compound contantaining Aldehyde Group AND Alcohol Group
* **Acid-Catalyzed:** H+, H2O * **Base-Catalyzed:** OH, H2O
31
*Reagents:* Acetal Cyclization ## Footnote **Starting Material:** Compound contantaining Ketone Group AND Alcohol Group
* **Acid-Catalyzed:** H+, H2O * **Base-Catalyzed:** OH, H2O
32
When is the *ring-formation* of cyclic hemiacetals/acetals favored?
Hemiacetal/Acetal cyclization reactions are *thermodynamically favorable* if the product is a ***five-membered ring*** or ***six-membered ring***.
33
Aldehyde/Ketone → Cyclic Acetal
Ethanediol Protection ## Footnote The *cyclic acetal* is highly stable/unreactive under **basic** conditions.
34
*Reagents:* Ethanediol Protection/Deprotection
* **Protection:** 1,2-Ethanediol, H3O+ * **Deprotection:** H3O+
35
Cyclic Acetal → Aldehyde/Ketone
Ethanediol Deprotection ## Footnote The *1,2-Ethanediol protection* of aldehydes/ketones is ***reversible***.
36
Properties of Cyclic Acetals
* Unreactive w/ Strong Nucleophiles * Highly Stable under Basic Conditions * Highly Unstable under Acidic Conditions ## Footnote The Ethanediol *deprotection* of aldehydes/ketones occurs in **acidic** conditions ONLY.
37
Cyclic Thioacetal → Aldehyde/Ketone
Ethanedithiol Deprotection ## Footnote The *1,2-Ethanedithiol protection* of aldehydes/ketones is ***reversible***.
38
Aldehyde/Ketone → Cyclic Thioacetal
Ethanedithiol Protection ## Footnote The *cyclic thioacetal* is highly stable/unreactive under **basic** conditions and **acidic** conditions.
39
*Reagents:* Ethanedithiol Protection/Deprotection
* **Protection:** 1,2-Ethanedithiol, ZnCl2 * **Deprotection:** HgCl2, H2O, CaCO3
40
Aldehyde/Ketone → Methylene Group | Cyclic Thioacetal
1. Ethanedithiol Protection 2. Raney-Nickel Reduction
41
*Reagents:* Raney-Nickel Reduction
Raney-Ni, H2
42
Cyclic Thioacetal → Methylene Group
Raney-Nickel Reduction
43
Imine
Any compound that contains a Carbon-Nitrogen double bond (C=N). ## Footnote The *nitrogen atom* of the imine is sp2-hybridized. (This hybridization causes the C=N–R structure to be *bent*.)
44
Enamine
A compound containing an *alkenyl substituent* attached to the Nitrogen atom. ## Footnote The Carbon atom of the C—N is double-bonded to another Carbon (C=C).
45
Aldehyde/Ketone → Imine
1° Amine Nucleophilic Addition | Ammonia Nucleophilic Addition ## Footnote The 1° amine nucleophilic addition to aldehydes/ketones occurs in **neutral** conditions OR **weakly acidic** (i.e. pH = 4–5) conditions.
46
*Reagents:* 1° Amine Elimination
H2O ## Footnote The 1° amine nucleophilic elimination ONLY occurs in **neutral** conditions OR **weakly acidic** (i.e. pH = 4–5) conditions.
47
*Reagents:* 1° Amine Nucleophilic Addition
R—NH2 | NH3 ## Footnote The *1° amine* can directly attack the carbonyl Carbon *without* protonation of the carbonyl Oxygen. (Primary amines are *stronger* nucleophiles that alcohols/water.)
48
Imine → Aldehyde/Ketone
1° Amine Elimination ## Footnote The 1° Amine nucleophilic addition to aldehydes/ketones is ***reversible***.
49
Why are *amines* stronger nucleophiles than *alcohols*?
* 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
Why is 1° Amine Nucleophilic Addition ineffective in *strongly* acidic conditions?
The 1° amine will become *fully protonated* (to yield NH4+/NH3R+) under acidic conditions; the NH4+/NH3R+ is ***not*** nucleophilic.
51
Hemiaminal
A compound containing one *alcohol* group (—OH) and one *amine* group bonded to the *same* sp3-hybridized carbon atom.
52
Iminium Ion
A compound that contains a Carbon-Nitrogen double bond (C=N) with a *positive charge* on the Nitrogen. ## Footnote The ***iminium ion*** is an intermediate compound formed during the 1°/2° *amine nucleophilic addition* to an *aldehyde/ketone*.
53
Oxocarbenium Ion
A compound containing an *Oxygen-substituted* carbonyl group with a *positive charge* on the Oxygen. ## Footnote The ***oxocarbenium ion*** is an intermediate compound formed during *acid-catalyzed* reactions involving an *aldehyde/ketone*.
54
Enol vs. Enolate
* **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). ## Footnote * 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
Hydrazone
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
Hydrazone → Methylene Group
Basic Decomposition of Hydrazone
57
Aldehyde/Ketone → Hydrazone
Hydrazine Addition
58
*Reagents:* Hydrazine Addition
H2N—NH2
59
*Reagents:* Decomposition of Hydrazone
NaOH
60
Aldehyde/Ketone → Methylene Group | Hydrazone
1. Hydrazine Addition 2. Decomposition of Hydrazone
61
Aldehyde/Ketone → Enamine
2° Amine Nucleophilic Addition
62
2° Amine Nucleophilic Addition
R2—NH
63
Why is the 3° Amine Nucleophilic Addition to aldehydes/ketones impossible?
The tertiary amine does *not* contain a Hydrogen atom that can be transfered to the oxide ion (following attack of the amine).
64
Cyanohydrin
A compound containing a *cyanide group* (—CN) and an *alcohol group* bonded to the *same* sp3-hybridized carbon atom.
65
Aldehyde/Ketone → Cyanohydrin
Cyanide Nucleophilic Addition ## Footnote The *first step* of the cyanide nucleophilic addition is ***reversible***
66
*Reagents:* Cyanide Nucleophilic Addition
NaCN, HCl ## Footnote The HCl must be *added slowly* to avoid the generation of the toxic HCN compound.
67
Aldehyde/Ketone → Alkene
Wittig Reaction | Nucleophilic Addition of Phosphorus Ylides ## Footnote The Witting Reaction allows for the creation of a *Carbon-Carbon double bond* (C=C).
68
*Mechanism:* Phosphorus Ylide Formation
1. SN2 Attack of 1°/2° Alkyl Halide by P(Ph)3 2. Deprotonation (from C—H bond) via Strong Base
69
Why are Triphenylphoshine *and* Phosphorus Ylides good nucleophiles? | P(Ph)3 = Triphenylphosphine
* **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
*Reagents:* Phosphorus Ylide Formation ## Footnote **P(Ph)3 =** Starting Reagent
1. 1°/2° Alkyl Halide 2. Organolithium Compound
71
Hydrazine
H2N—NH2