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Organic Chem 2 > Enolate chemistry (condensation and conjugate addition) > Flashcards

Enolate chemistry (condensation and conjugate addition) Flashcards

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1
Q

Factors that effect the acidity of alpha carbons of various carbonyl compounds

A

Inductive effects
resonance localization
increasing electronegativity of the atom

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2
Q

Esters are ___ acidic than aldehydes or ketones

A

Less

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3
Q

ENolates are most nucleophilic at the

A

carbon

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4
Q

Nearly all of the negative charge on an enolate is on

A

the oxygen

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5
Q

overlap first then

A

deprotonation

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6
Q

enolate formation requires that the C-H bond

A

align parallel to the carbonyl bond

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7
Q

aligned enolates are

A

acidic

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8
Q

non aligned enolates are

A

not acidic

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9
Q

SN2 reactions are

A

MO controlled

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10
Q

MO controlled

A

for the reaciton ot proceed there should be good overlap oof the nucleophile and the sigma C-X bond of the electrophilek

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11
Q

keto-enol tautomerization via enolates mechanism

A
  • Break C-H
  • Form O-H
    -Break C-O
  • Form C-C
  • Form O-H
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12
Q

Deuterium

A

An isotope of hydrogen with one proton and one neutron in the nucleus having an atomic weight of 2.014

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13
Q

deuterium labelling does no occur on

A

the beta carbons

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14
Q

deuterium labelling

A

using deuterium to replace all hydrogens on a structure to label it

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15
Q

racemate

A

a mixture containing equal amounts of two enantiomers

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16
Q

racemization

A

the chemical reaction resulting in the conversion of L amino acids to D amino acids for amino acid dating

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17
Q

chiral center

A

carbon with four different substitutions and a lack a plane of symmetry

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18
Q

one conquesunce of enolates being flat

A

chiral centers on alpha carbon undergo reacemization

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19
Q

why does racemization occur

A

due to the ability of things to add to the top or bottom of an enolate

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20
Q

epimerization

A

the reversible the interconversion of epimers

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21
Q

epimer

A

diasteromers that differ at only one chiral center

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22
Q

diasteromer

A

stereoisomers that are NOT mirror images thus they have different physical properties and optical rotations

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23
Q

enolate

A

intermediate
stabilized by resonance
enol & base— enolate

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24
Q

unsymmetrical ketones can form

A

two different enolates

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25
Q

kinetic enolate

A

less substituted enolate
formed quickly
removal of an acidic alpha hydrogen
image

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26
Q

kinetic control

A

a reaction in which the product ration is determined by the rate at which the products are formed

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27
Q

thermodynamic control

A

a reaction in which the product ratio is determined by the relative stability of the products

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28
Q

thermodynamic enolate

A

more substituted double bond
higher activation energy
more thermodynamically stable
image

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29
Q

lithium di-isopropyl amide

A

image

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30
Q

LDA is

A

strong bulky base

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31
Q

how to make a kinetic enolate

A

selectively using a strong bulky base at a low temperature

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32
Q

how to make a thermodynamic enolate

A

can make selectively by reading with RO-/ ROH and setting up an equilibrium mixture of enolates

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33
Q

less substituted alpha carbon will

A

be deprotonated faster

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34
Q

which could make deprotonation harder

A

steric interactions

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35
Q

kinetic vs thermodynamic energy diagram

A

Image

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36
Q

which enolate is less stable

A

kinetic enolate

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37
Q

which enolate is more stable

A

thermodynamic enolate

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38
Q

halogenation of enolates in thermodynamic conditions

A

substitution at the most substituted carbon

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39
Q

halogenation of enolates in kinetic conditions

A

additional the least substituted carbon

40
Q

alkylation of enolates in thermodynamic conditions

A

addition to the most substituted carbon

41
Q

alkylation of enolates in kinetic conditions

A

addition to the least substituted carbon

42
Q

alkylation is restricted to

A

primary, allylic, and benzylic electrophiles

43
Q

aldol

A

contains both aldehyde and alcohol functional groups
image

44
Q

thermodynamic aldol formation requires

A

two steps and heat for the aldol condensation product

45
Q

what can occur between ketones

A

aldol condensations

46
Q

aldol addition mechanism of thermodynamic aldol

A

1) protonation (annotate formation)
2) elimination

47
Q

thermodynamic aldol conditions lead to what kind of reaction

A

E1, because it is a conjugate base mechanism that occurs in multiple parts

48
Q

an intramolecular aldol reaction is the second step to the

A

Robinson annulation rection

49
Q

in a mixture of two aldehydes

A

a mixture of enolates will form

50
Q

each enolate will react

A

with itself and another aldehyde

51
Q

nonenolizable aldehyde

A

image

52
Q

nonenolizable aldehyde + symmetric ketone

A

makes a cross aldol product

53
Q

kinetic aldol conditions are predictable

A

high selectivity at low temperature under non-aqueous conditons

54
Q

reagents for thermodynamic aldol condensation

A

NaOH & H20, NaOH & H20 & heat

55
Q

reagents for kinetic aldol condensation

A

LDA, low temp, aldehyde, acid workup

56
Q

ester enolate reaction is called

A

clauses condensation

57
Q

clasien condensation

A

enolate ion of one ester acts as nucleophile attacking another ester

58
Q

clausien condensation product

A

image

59
Q

transesterfication is competitive with

A

the claisen

60
Q

always match he ester group with

A

the base used

61
Q

clauses condensation mechanism

A

1) deprotonation of ester alpha carbon to give an ester enolate
2) attack of enolate on a second equivalent ester
3) elimination of RO(-)
- Acid base reaction of beta-keto ester prodyct
4) mils acid quench
image

62
Q

beta-keto ester

A

image

63
Q

acid base reaction of beta- keto ester

A

the enolate is not basic enough to deprotonate starting ester so all the RO- is consumed

64
Q

quenching of the reaction

A

image

65
Q

crossed claisen product

A

joins two different esters

66
Q

Dieckmann condensation

A

intramolecular clauses condensation

67
Q

thermal decarboxylation

A

image

68
Q

beta-keto carboxylic acid

A

image

69
Q

most carboxylic acids do not

A

spontaneously lose CO2

70
Q

beta keto acid ____ CO2 upon heating

A

loses

71
Q

acetic acid, butanoic acid, alpha keto acid, and gamma keto acid all boil without

A

losing CO2

72
Q

mechanism of decarboxylation of beta-ketoacids

A

cyclic concerted transition start that results in the formation of an enol intermediate

73
Q

aceoacetic ester synthesis

A

image

74
Q

maolonic ester synthesis

A

the process by which to convert a Masonic ester to a carboxylic acid

75
Q

Malonic ester synthesis mechanism

A

1) CH3O- acts as a base to remove acidic proton and create enolate
2) Enolate acts as a nucleophile to attack alkyl halide in the Sn2 reaction
3) addition of aqueous acids leads to hydrolysis of esters into carboxylic acids
4) decarboxylation occurs to form enol and carbon dioxide

76
Q

strong acids can cause

A

racemization

77
Q

ketones are

A

chiral

78
Q

enrols are

A

achiral

79
Q

halogenation of ketones are slow withou

A

acid

80
Q

halogenation of ketone bond breaking and formation

A

break C-C, form C-X, Form C-O, break O-H

81
Q

acid catalyzed aldol condensation bond breaking and formation

A

Form C-O, Break C-C (pi) & form C-C, break C-O pi, Break O-H

82
Q

acid catalyzed aldol condensation mechanism

A

1) keto enol tautomerimsm
2) protonation, form O-H
3) elimination, form C-O
4) deprotonation, break O-H

83
Q

H20 is a. ____ leaving group than OH-

A

better

84
Q

Mannich reaction

A

compounds capable of forming an enol react with imines from formaldehyde and a primary or secondary amine to yield beta-aminoalkyl carbonyl compounds

85
Q

mannich reaction mechanism

A

image

86
Q

mannich reaction reagents

A

O=CH2, CH3CH2NH2, HCl

87
Q

conjugation addition

A

is the addition of a nucleophile to a pi-bond conjugated with electron withdrawing groups such as C=O, CN, or NO2

88
Q

conjugates addition can also be called a

A

1,4 addition

89
Q

Michael reaction gives

A

1,5 diketones

90
Q

1,5 diketone

A

image

91
Q

Michael reaciton mechanism

A

1) enolate formation
2) conjugate addition

92
Q

Michael reaction

A

1,4 nucleophilic addition of enolate anion or enamine to a,b-unsaturated carbonyl (done over EtO- and EtOH)
image

93
Q

Robinson annulation

A

A reaction that collectively constituted the following reactions:

—> Michael addition followed by Intramolecular Aldol Condensation followed by Dehydration

94
Q

Michael reaction reactants

A

NaOH, Ketone

95
Q

Robinson annulation reactants

A

KOH, CH3OH, heat

96
Q

robinson annulation mechanism

A
  1. Michael addition
  2. aldol reaction
  3. condensation, E1CB

Organic Chem 2 (4 decks)

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