Alpha Carbon Chemistry: Enols & Enolates

Question 1

What is the mechanism for acid-catalyzed tautomerization?

Answer 1

1. Proton Transfer
2. Proton Transfer

Question 2

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

Answer 2

Alpha

Question 3

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

Answer 3

Enol

Question 4

Enols are stable because why?

Answer 4

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

Question 5

What is the mechanism for base-catalyzed tautomerization

Answer 5

1. Proton Transfer
2. Proton Transfer

Question 6

The alpha position of enols _____ due to resonance structure.

Answer 6

Nucleophilic

Question 7

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

Answer 7

Enolate

Question 8

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

Answer 8

Enolate

Question 9

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

Answer 9

O-attack

Question 10

When the alpha carbon attacks an electrophile its called a __________

Answer 10

C-attack

Question 11

Enolates are more useful than enols because why:

Answer 11

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

Question 12

Only ______ protons of an aldehyde or ketone is acidic

Answer 12

Alpha protons

Question 13

Aldehyde and ketones pka is usually what?

Answer 13

16-20

Question 14

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

Answer 14

Enolate

Question 15

_______ is a base used to form enolates

Answer 15

LDA lithium diisopropylamide

Question 16

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

Answer 16

halogenation

Question 17

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

Answer 17

1. Proton transfer
2. Proton transfer
3. Nucleophilic attack
4. Proton transfer

Question 18

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

Answer 18

More substituted

Question 19

The halogenated product can undergo elimination when treated with a _____

Answer 19

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

Question 20

What is the hell-volhard-zelinsky reaction?

Answer 20

Alpha bromination of carboxylic acids

Question 21

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

Answer 21

Special reagent

Question 22

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

Answer 22

PBr₃

Question 23

Ketones can undergo alpha halogenation in _____

Answer 23

Basic Conditions

Question 24

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

Answer 24

1. Proton transfer
2. Proton transfer
3. Nucleophilic attack
4. Proton Transfer

Question 25

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

Answer 25

Alpha

Question 26

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

Answer 26

Twice

Question 27

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

Answer 27

carboxylic acid

Question 28

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

Answer 28

NaOH, Br₂/ H₃O⁺

Question 29

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

Answer 29

Has no alpha protons

Question 30

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

Answer 30

Aldol addition reaction

Question 31

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

Answer 31

Beta-hydroxy

Question 32

What is the mechanism for an aldol addition reaction?

Answer 32

1. Proton transfer 2. Nucleophilic attack 3. Proton transfer

Question 33

For most simple aldehydes equilibrium favors the \_\_\_\_\_\_\_\_

Answer 33

Aldol product

Question 34

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

Answer 34

Ketone

Question 35

Retro aldol reaction

Answer 35

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

Question 36

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

Answer 36

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

Question 37

Aldol condensation

Answer 37

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

Question 38

The product of an aldol condensation is an \_\_\_\_\_\_\_\_\_\_\_\_\_

Answer 38

alpha, beta-unsaturated aldehyde or ketone

Question 39

What is the mechanism for an aldol condensation reaction?

Answer 39

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

Question 40

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

Answer 40

Fewer steric interaction

Question 41

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ are aldol reactions that cab occur between different reactants

Answer 41

Crossed or mixed aldol reactions

Question 42

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

Answer 42

Alpha proton

Question 43

Cross aldol reaction can also be formed with \_\_\_\_\_\_\_\_\_\_\_

Answer 43

Benzaldehyde

Question 44

Aldol reaction using aromatic aldehydes generally produce \_\_\_\_\_\_\_\_\_\_\_\_\_\_

Answer 44

Condensation reactions

Question 45

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

Answer 45

LDA

Question 46

Compounds that have __________ can undergo intramolecular aldol reaction

Answer 46

two carbonyl groups

Question 47

Intramolecular aldol reaction show preference for formation of ___________ member rings

Answer 47

5 & 6

Question 48

Claisen condensation

Answer 48

Is a reaction where esters also exhibit reversible condensation reactions

Question 49

In a clasien condensation reaction with ester use a base that has \_\_\_\_\_\_\_\_\_\_\_

Answer 49

The sam eester group

Question 50

What is the mechanism for claisen condensation reactions?

Answer 50

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

Question 51

The product of a Claisen condensation reaction is a \_\_\_\_\_\_\_\_\_\_

Answer 51

Beta-keto ester