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Organic Chemistry > Alpha Carbon Chemistry: Enols & Enolates > Flashcards

Alpha Carbon Chemistry: Enols & Enolates Flashcards

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1
Q

What is the mechanism for acid-catalyzed tautomerization?

A
  1. Proton Transfer
  2. Proton Transfer
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2
Q

The carbon next to the carbonyl group is an _____ carbon & it has _____ protons

A

Alpha

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3
Q

In the presence of a catalytic acid or base is present a ketone will exist on equilibrium with an ______

A

Enol

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4
Q

Enols are stable because why?

A
  1. They have a conjugated pie system which stabilizes it
  2. They can form hydrogen bonds
  3. An example of an enol is phenol
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5
Q

What is the mechanism for base-catalyzed tautomerization

A
  1. Proton Transfer
  2. Proton Transfer
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6
Q

The alpha position of enols _____ due to resonance structure.

A

Nucleophilic

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7
Q

When treated with a strong base the ketone alpha position is deprotonated to form an intermediate called __________

A

Enolate

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8
Q

An _____ is an ambident nucleophile because it can attack from two places the negative charge oxygen & the alpha carbon.

A

Enolate

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9
Q

When the negative charge oxygen attacks an electrophile is called an ________

A

O-attack

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10
Q

When the alpha carbon attacks an electrophile its called a __________

A

C-attack

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11
Q

Enolates are more useful than enols because why:

A
  1. Enolates posses full negative charge & more reactive than enols
  2. Enolates can be isolated
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12
Q

Only ______ protons of an aldehyde or ketone is acidic

A

Alpha protons

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13
Q

Aldehyde and ketones pka is usually what?

A

16-20

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14
Q

An alkoxide ion can be used as a base or a sodium hydride (H-) to convert aldehyde into an _______

A

Enolate

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15
Q

_______ is a base used to form enolates

A

LDA lithium diisopropylamide

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16
Q

Under acid-catalyzed conditions, ketones & aldehydes will undergo _________ at the alpha position

A

halogenation

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17
Q

What is the mechanism for acid-catalzyed halogenation of ketones?

A
  1. Proton transfer
  2. Proton transfer
  3. Nucleophilic attack
  4. Proton transfer
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18
Q

When an unsymmetrical ketone is used, bromination occurs primarily at the ________ position of the ketone

A

More substituted

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19
Q

The halogenated product can undergo elimination when treated with a _____

A

Base (any base can be used such as pyridine or Li2CO3 or t-BUTOK)

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20
Q

What is the hell-volhard-zelinsky reaction?

A

Alpha bromination of carboxylic acids

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21
Q

Alpha halogenation can occur easily with ketones & aldehydes however carboxylic acids, esters, or amides can’t do it easily & need a _____

A

Special reagent

22
Q

Carboxylic acids can undergo alpha halogenation when treated with bromine in the presence of ______ which is

A

PBr3

23
Q

Ketones can undergo alpha halogenation in _____

A

Basic Conditions

24
Q

What is the mechanism for acid-catalyzed halogenation of ketones?

A
  1. Proton transfer
  2. Proton transfer
  3. Nucleophilic attack
  4. Proton Transfer
25
Q

Under acid-catalyzed conditions, ketones & aldehydes will undergo halogenation at the _____ position

A

Alpha

26
Q

In basic conditions, if there is more than one alpha proton available, the reaction will occur ____

A

Twice

27
Q

When a methyl ketone is treated with excess base & excess halogen a _______ is formed (halofrom reaction)

A

carboxylic acid

28
Q

When a methyl ketone is treated with __________ a haloform reaction occurs where it form a carboxylic acid

A

NaOH, Br2/ H3O+

29
Q

Haloform reaction is most efficient when the other side of the ketone has _________

A

Has no alpha protons

30
Q

When an aldehyde is treated with sodium hydroxide a _________ reaction occurs

A

Aldol addition reaction

31
Q

The product of an aldol addition reaction is always a _________ aldehyde or ketone

A

Beta-hydroxy

32
Q

What is the mechanism for an aldol addition reaction?

A
  1. Proton transfer
  2. Nucleophilic attack
  3. Proton transfer
33
Q

For most simple aldehydes equilibrium favors the ________

A

Aldol product

34
Q

For most Ketones the _______ is the favored product in equilibrium in an aldol reaction

A

Ketone

35
Q

Retro aldol reaction

A

Is the reverse process of an aldol addition reaction so an aldol reaction converts back to an aldehyde or ketone

36
Q

When treated in acidic or basic conditions, the product of an aldol addition reaction will undergo elimination to produce ___________

A

Unsaturation between the alpha & beta position (double bond between alpha and beta position)

37
Q

Aldol condensation

A

When aldol addition & dehydration occur at the same time (water is lost)

38
Q

The product of an aldol condensation is an _____________

A

alpha, beta-unsaturated aldehyde or ketone

39
Q

What is the mechanism for an aldol condensation reaction?

A
  1. Proton transfer
  2. Nucleophilic attack
  3. Proton transfer
  4. Proton transfer
  5. Loss of LG
40
Q

When two stereoisomeric pie bonds are formed the product with ________ is the major product

A

Fewer steric interaction

41
Q

_______________ are aldol reactions that cab occur between different reactants

A

Crossed or mixed aldol reactions

42
Q

If one aldehyde lack an _______ & has an unhindered carbonyl group then a cross-reaction can be used

A

Alpha proton

43
Q

Cross aldol reaction can also be formed with ___________

A

Benzaldehyde

44
Q

Aldol reaction using aromatic aldehydes generally produce ______________

A

Condensation reactions

45
Q

Cross-aldol reaction can also be performed using _______ as a base

A

LDA

46
Q

Compounds that have __________ can undergo intramolecular aldol reaction

A

two carbonyl groups

47
Q

Intramolecular aldol reaction show preference for formation of ___________ member rings

A

5 & 6

48
Q

Claisen condensation

A

Is a reaction where esters also exhibit reversible condensation reactions

49
Q

In a clasien condensation reaction with ester use a base that has ___________

A

The sam eester group

50
Q

What is the mechanism for claisen condensation reactions?

A
  1. Proton transfer
  2. Nucleophilic attack
  3. Loss of LG
  4. Proton Transfer
51
Q

The product of a Claisen condensation reaction is a __________

A

Beta-keto ester

Organic Chemistry (47 decks)

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