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ORGO 2 > Unit 5 (Lesson 28-33) > Flashcards

Unit 5 (Lesson 28-33) Flashcards

1
Q

true/fasle: the alpha hydrogen of the carbonyl compound is significantly more acidic than a typical hydrogen

A

true
- electron withdrawing effect of the C=O
- resonance stabilization of the resulting negative charge

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2
Q

[keto-enol tautomerization] carbonyl is in equilibrium with it’s enol form when under

A
  • acidic conditions
  • due to acidity of alpha hydrogen of carbonyl compound
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3
Q

alpha - halogenation:

A

acid-catalyzed halogenation of a carbonyl

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4
Q

single halogenation

A
  • under acidic conditions
    oxygen of carbonyl has less e- density because of e- withdrawing halogen
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5
Q

multiple halogenation

A

alpha proton is more acidic because of e- withdrawing halogen

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6
Q

tautomerization

A

a process where two isomers interconvert in rapid equilibrium

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7
Q

why is the carbonyl isomer (aldehyde or ketone) favored in nearly every case

A

due to the stability of the C=O
- notable exception is phenol

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8
Q

why do dicarbonyls form a greater amount of enol at equilibrium

A

due to hydrogen bonding between the enol OH and the neighboring carbonyl oxygen

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9
Q

under acid catalyzed conditions, tautomerization begins with

A

protonation

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10
Q

under basic conditions tautomerization begins with

A

deprotoation

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11
Q

alpha hydrogens

A

hydrogens on the carbon immediately bonded to carbonyl carbon

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12
Q

how many resonance forms do alpha hydrogens have

A

2

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13
Q

electron donation towards the carbonyl (resonance or induction) increases/decreases alpha hydrogen acidity

A

decreases

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14
Q

electron withdraw away from the carbonyl (resonance or induction) increases/decreases alpha hydrogen acidity

A

increases

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15
Q

if the nitrogen of an amide possesses a hydrogen, that hydrogen is more/less acidic than the amides’ alpha hydrogen

A

more

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16
Q

what makes LDA a poor nucleophile

A

sterics
- if you want something to act as a base only – LDA is a good choice

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17
Q

enolate formation with LDA

A

LDA is the best base for enolate formation

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18
Q

kinetic conditions for enolate formation (used in alkylation)

A
  • no equilibrium
    LEAST SUB CARBON
  • the carbonyl compound i slowly added to a slight excess of strong base
  • reaction carried out at LOW temperature (78 degrees)
  • aprotic solvents (THF, ethyl ether) are used
  • less substituted double bond
    less stable
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19
Q

thermodynamic conditions of enolate formation

A
  • equilibrium
    MOST SUB CARBON
  • the base is slowly added to the solution
  • reactions are carried out at higher temperatures
  • protic sovlents (ROH) can be added to the reaction
  • more substituted double bond
  • more stable
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20
Q

aldol addition

A

–a nucleophilic addition reaction between an enolate and an aldehyde or ketone electrophile, forming a B-hydroxy carbonyl product
–addition to carbonyl group at alpha position of seperate carbonyl group
- rxn is reversivble
- new C-C bond
- efficient for prepartation of B-hydroxy aldehydes and ketones

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21
Q

negative Keq value for enolate equilibrium

A

reactant favored

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22
Q

positive Keq value for enolate equilibrium

A

product favored

23
Q

what happens when you use an alkoxide or hydroxide for enolate formation

A

only a small amount of enolate is generated - carbonyl is favored

24
Q

for a di-carbonyl system, is it generally reactant or product favored if you use an alkoxide or hydroxide

A

product favored
- irreversibly favor enolate formation

25
Q

alpha halogenation occurs on what

A

aldehydes and ketones

26
Q

what can an alpha-halogenated product be treated with to forma a beta-unsaturated product

A

a big bulky strong base

27
Q

what kind of ketone allows you to create either a kinetic or thermodynamic product

A

non-symmetrical ketone

28
Q

how to get a kinetic enolization

A

use light excess of LDA (1.05 eq) at a cold temp (-78 degrees)

29
Q

how to get a thermodynamic enolization

A

use a slight deficiency of LDA (0.95 eq) at a warmer temp (0 degrees)
- kinetic enolate forms first, but reacts with the 0.05 starting material in an acid base reaction to create the thermodynamic enolate
- can add 0.05 methanol to increase yield o f thernodynamic enolate

30
Q

self aldol addition

A

occur when an aldehyde or ketone is reacted under basic conditions at room temperatue

31
Q

what is an aldol condensation

A

a nucleophilic addition reaction between an anolate and an aldehyde or ketone electrophile, followed by a E1CB dehydration to form an alpha-beta-unsaturated carboyl product
- kicks off OH, makes c=c bond

32
Q

what purpose does heat have when you see a ketone or aldehyde with a strong base and water

A

heat is the key that it is a dehydration mechanism and not a regular aldol addition

33
Q

controlling products of crossed aldol addition

A

if one component has no acidic alpha hydrogens, the second carbonyl compound can be added slowly to solution, giving mostly one product

34
Q

steps for a crossed aldol addition

A

form desired enolate first using LDA, then slowly add the second carbonyl compound (so it doesn’t react with itself)

35
Q

type 1 crossed aldol addition

A
  • both aldehydes and ketones possess enolizable alpha hydrogens
  • enlolate nucleophile prepared with LDA, then desired electrophilic aldehyde/ketone is added slowly
  • acid workup required
36
Q

type 2 crosses aldol addition

A
  • one species lacks alpha hydrogen
  • enlolate cannot be generated from an aldehyde/ketone that lacks alpha hydrogens – this aldehyde/ketone will serve as the electrophile
37
Q

steps for type 2 crossed aldol addition

A
  • species lacking alpha hydrogens is first dissolved in basic solution
  • then aldehyde/ketone is added slowly - molecule will then enolize and attack the species lacking
38
Q

claisen condensation

A
  • similar to Aldol condensation, but with esters
  • efficient method for preparing B-keto esters
  • same ester and alkoxide(reagent) must be used to prevent transesterification of the ester
    Ex:
    1.) NaOCH3, HOCH3
    2.) H2O, HCl (no heat)
39
Q

why are claisen condensations irreversible

A

due to the increased acidity of the alpha hydrogen

40
Q

what relationship do you need to have to undergo the loss of CO2 upon heating

A

alpha-beta relationship to make carboxylate

41
Q

what leads to an alpha-beta unsaturated carbonyl compound undergoing a 1,2 addition

A

kinetic product aka direct addition
- strong nucleophiles
RMgX
RLi
NaBH4
LiAlH4

42
Q

what leads to an alpha-beta unsaturated carbonyl compound undergoing a 1,4 addition

A

thermodynamic product aka conjugate addition
- weak nucleophiles
CH3OH
H2O
RNH2
Cl-
Br-
-CN
CHSH

43
Q

Michael Reaction

A

1,4 addition of stabilized carbon nucleophiles to alpha-beta unsaturated carbonyl compounds
- conjugate addition of stabilized anions (enolates) forms new carbon-carbob bonds
- formation of a 1,5 di-carbonyl

44
Q

What does michael addition work well with

A
  • stabilzed carbon nucleophiles
  • they add like weake bases -CN, -Br, etc
  • when you see a beta compound ***
45
Q

robinson annulation

A
  • a michael reaction followed by an aldol addition then dehydration
  • hallmark indicator of a Robinson annulation is the FORMATION OF A 6-MEMBERED RING
  • often product is an alpha-beta unsaturated ketone
46
Q

dieckmann condensations

A
  • an intramolecula nucleophilic acyl substitution between an enolate and an ester electrophile, cyclizing to form a cyclic beta-ketp carbonyl
47
Q

1,6 dieckmann condensation

A

forms 5 membered ring
- 1 attacks 5

48
Q

1,7 dieckmann condensation

A

1 attacks 6
forms 6 membered ring

49
Q

robinson annulatio indicator

A

base/heat/carbonyl with alyene

50
Q

malonic ester synthesis

A
  • synthetic route to prepare a carboxylic acid with a desired chain length
51
Q

malonic ester starting material

A
  • diester
  • matching alkoxide
  • RX
  • H2O, HCL, heat
52
Q

acetoacetic ester synthesis

A
  • ketoeter
  • matching alkoxide
  • RX
  • H2O, HCl, heat
53
Q

acetoacetic ester synthesis

A
  • makes ketones
54
Q

how to recognize an Aldol addtition

A

NaOH, H2O, 0 degrees

ORGO 2 (10 decks)

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