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ORGO 2 > Unit 3 (Lesson 14-20) > Flashcards

Unit 3 (Lesson 14-20) Flashcards

1
Q

lithium reagents are typically used as

A

strong bases

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2
Q

Grignard reagents are perferred when acting as

A

nucleophile with epoxides and carbonyls

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3
Q

when the rxn is of a grignard + epoxide, you attack

A

the least hindered carbon and maintain stereochemistry

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4
Q

acidic proton with grignard

A

rxn will end up with starting material

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5
Q

reactivity of aldehydes and ketones in nucleophilic addition reactions

A

formaldehyde>aldehyde>ketone

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6
Q

alkyl groups are electron donating through

A

hyperconjugation and make C=O carbon less positive

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7
Q

as steric hindrance of the carbonyl increases

A

the reactivity toward nucleophilic addition decreases

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8
Q

order of nucleophilic reactivity

A

acid chlordide> acid anhydride> aldehyde > ketone > carboxylic acid > amide

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9
Q

grignard rxn with formaldehyde produces

A

primary alcohol

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10
Q

grignard rxn with aldehyde produces

A

secondary alcohol + (enantiomer sometimes)

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11
Q

grignard rxn with ketone produces

A

tertiary alcohol + (enantiomer sometimes)

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12
Q

what can be used to synthesize a carboxylic acid

A

addition of CO2 to a grignard

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13
Q

when a carbon is associated with a metal (Mg, Li, Cu), the carbon is the more/less electronegative atom and takes on a partial () character

A

more, negative

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14
Q

ether/solvent that Mg is added to

A

Et2O or THF

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15
Q

what conditions promote the conversion of acetone to acetone cyanohydrin

A

HCL, excess NaCN

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16
Q

cyanohydrin can be converted back into an aldehyde or ketone in the addition of a

A

base

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17
Q

strong acid/weak base =

A

good LG

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18
Q

strong base/weak acid =

A

poor LG

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19
Q

NaBH4

A
  • more selective
  • only reduces aldehydes and ketones
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20
Q

LiAlH4

A
  • less selective, more reactive
  • reduces aldehydes, ketones, esters, carboxylic acids, nitriles, amides
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21
Q

why do NaBH4 and LiAl4 require H3o+

A

they require an aqueous workup to protonate the alkoxide

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22
Q

things that add irreversibly

A

NaBH4, LiAlH4, RMgX, or RLi

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23
Q

ketone /aldehyde + water (+acid/base catalyst)

A

hydrate

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24
Q

degree of hydration at equilibrium (K)

A

= [hydrate]/starting aldehyde/ketone

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25
Q

degree of hydration trends

A

as K increases, more hydrate is formed

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26
Q

why is an aldehyde with F3C instead of CH3 so reactive

A

so reactive because it’s electron withdrawing

27
Q

aldehydes and ketones are in equilibrium with their acetals in the presence of ()

A

alcohol

28
Q

hemi-acetal

A

1OR + 1 OH

29
Q

acetal

A

OR + OR

30
Q

to favor acetal formation

A

add more (CH3OH], remove water

31
Q

to favor aldehyde formation

A

increase [H2O] and remove methanol

32
Q

acetal hydrolysis

A
  • follows same mechanism as an acetal formation, but in reverse
  • acetals are good protecting groups –>
33
Q

reducing agents we’ve used

A

H2/Pd
H2NNH2, KOH, heat
NaHB4
DIBALH
LiAlH4

34
Q

reduction refers to

A

the addition of H2 or removal of oxygen

35
Q

Oxidation refers to

A

the addition of oxygen or removal of H2

36
Q

oxidizing agents for this course

A

PCC
H2CrO4

37
Q

hydrogenation

A

H2 pd/c
- only benzylic
- reduces benzylic carbonyls to methylenes

38
Q

wolff-kischner – H2NNH2, KOH, heat

A

reduces all carbonyls to methylenes

39
Q

primary alcohol oxidations - anhydrous conditions with ()

A

PCC

40
Q

primary alcohol oxidations - aqueous with ()

A

Chromate (H2CrO4)

41
Q

PCC + a secondary alcohol makes a ()

A

ketone

42
Q

to form an imine you use a () amine

A

primary

43
Q

to form an enamine you use a () amine

A

secondary

44
Q

enamines have

A

2 R groups and a double bond in the ring

45
Q

imines have

A

1 R group and a double bond between N and C on ring

46
Q

imine reduction is a useful method for

A

synthesizing secondary amines

47
Q

true/false: imines are more reactive than ketones and aldehydes

A

true – they can selectively reduce with H2, Pb/C, or NaBH3CN

48
Q

what does a wittig reaction do

A

replace carbonyl with alkene

49
Q

first step in wittig reaction

A

generate phosphonium ylide

50
Q

weak compounds add via ()

A

conjugate addition
- more stable, weak bases
1,4 - Addition

51
Q

strong compounds ad via ()

A

direct addition
- strong base, nuc
1,2 - Addition

52
Q

addition to a weak base is () and driven by ()

A

reversible, thermodynamic control

53
Q

secondary alcohols oxidize to form ()

A

ketones, regardless of oxidizing agent

54
Q

primary alcohols can be oxidized to form () or ()

A

aldehydes (mild oxidation)
carboxylic acids (strong oxidation)

55
Q

can tertiary alcohol be oxidized

A

no

56
Q

true/fasle: when aldehydes and ketones are attacked by a carbon nucleophile or a hydride donor, there is no leaving group in the tetrahedral intermediate

A

true

57
Q

when aldehydes and ketones react with water, alcohols, or amines (1 & 2), they undergo what

A

a nucleophilic-addition-elimintation mechanism

58
Q

what are the optimal pH conditions for imines and enamines to be formed

A

~ 4.5

59
Q

imine and enamine formation at a low pH

A

pH must be acidic enough to promote the dehydration step (elimination of H2O), however if solution is too acidic, the amine present will deprotonate, decreasing the availability of nucleophilic amine in the mixture

60
Q

inamine and enamine formation at a high pH

A

if the solution isn’t acidic enough, protonation of the hemiaminal intermediate is less effective and the rate decreases

61
Q

imine formation last step

A

deprotonation

62
Q

enamine formation last step

A

elimination of an alpha hydrogen to for a C=C, which breaks the C-N Pi bond

63
Q

steps to go from hemiacetal to acetal

A

protonate, eliminate water, nucelophilic addition, deprotonate

64
Q

reversion to carbonyl occurs when acetals are reacted with ()

A

water and acid

ORGO 2 (10 decks)

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