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CHEM 2420- organic chem 2 > Aldol and Michael reactions > Flashcards

Aldol and Michael reactions Flashcards

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1
Q

what do we get when we subject a ketone to basic conditions

A

an enolate (ketone with a negative charge at the alpha position)

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2
Q

which side of the ketone-enolate equilibrium is favoured under basic conditions

A

ketone

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3
Q

how can we make the ketone-enolate equilibrium favor the enolate

A

by using a stronger base

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4
Q

what do we get when an enolate reacts with an electrophile

A

electrophilic addition at the alpha position

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5
Q

what do we get when the enolate and ketone are mixed together

A

enolate attacks the ketone, and we get an aldol (new C-C bond made, add the alcohol version of the ketone onto the enolate)

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6
Q

what is another name for an aldol

A

b-hydroxy ketone

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7
Q

what is an aldol

A

an alcohol ketone (a carbonyl with an OH at the beta position)

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8
Q

what do we get if an aldol reaction is heated

A

water is released from the aldol, and we get a double bond between alpha and beta (a,b-unsaturated ketone aka enone)

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9
Q

what is an enone

A

a carbonyl with a double bond between a and b positions

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10
Q

what is another name for an enone

A

a,b-unsaturated ketone

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11
Q

what reaction is an enone a product of

A

aldol condensation

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12
Q

T or F: you need heat for aldol condensation

A

true

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13
Q

if there is no heat in the aldol condensation reaction, what type of reaction is it

A

a simple aldol reaction

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14
Q

what is the product of the aldol reaction (give both names)

A

b-hydroxy ketone

aldol

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15
Q

what is the product of the aldol condensation reaction (give both names)

A

a,b-unsaturated ketone

enone

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16
Q

T or F: aldol reactions may be intramolecular

A

true

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17
Q

what are the conditions for the intramolecular aldol reaction

A

must have at least 2 carbonyls on the molecule, and it would need to form a 5 or 6 membered ring

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18
Q

what happens in the crossed aldol reaction (ie what is reacting)

A

we start with our enolate and react is with an electrophile which is another carbonyl

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19
Q

what is one complication with crossed aldol reactions

A

the second carbonyl may become an enolate itself, and produce a side product known as an enal (a,b-unsaturated aldehyde)

20
Q

what is the product of a crossed aldol reaction when the second carbonyl becomes an enolate itself (give both names)

A

enal or a,b-unsaturated aldehyde

21
Q

how can we avoid enal production in crossed aldol reactions

A

we can use a carbonyl that has no alpha hydrogens (because then the molecule cannot be deprotonated to become an enolate)

22
Q

what is the claisen reaction (name the starting product, what is used, and what is produced)

A

we start with an ester and react it with a base, producing an ester enolate

23
Q

what is the product of an ester reacting with base

A

ester enolate

24
Q

what is the product when an ester enolate attacks the starting ester

A

b-keto ester

25
Q

what types of bases are used in the claisen condensation reaction

A

OR- rather than OH- so we don’t get side products

26
Q

T or F: the claisen condensation reaction requires an acid work up (why)

A

true; it quenches the double enolate formed

27
Q

why doesnt the claisen reaction produce an aldol or an unsaturated double bond?

A

OCH3- leaves during the mechanism (super important step)

28
Q

how do we create a new C-C bond onto a claisen product

A

react it with RX (alkylation)

29
Q

what happens when a claisen reaction is heated in acidic conditions

A

CO2 is released from the b-keto ester = ketone

30
Q

describe the michael reaction

A

ketone reacts with base and heat to produce an enone

31
Q

what is an enone

A

a,b-unsaturated ketone

32
Q

T or F: an enone has resonance structures

A

true

33
Q

what do the resonance structures of an enone show

A

the b position is electrophilic (positively charged)

34
Q

what happens to an enone in the presence of a nucleophile

A

nucleophile attack on the b carbon, followed by protonated

beta addition occurs

35
Q

what type of nucleophiles work best in michael reactions

A

ones that are a resonance stabilized enolate: ie RMgBr or R2CuLi

36
Q

nucleophiles for michael additions are michael (donors/acceptors)

A

nuc= michael donor

37
Q

electrophiles for michael additions are michael (donors/acceptors)

A

electrophiles = michael acceptors

38
Q

what type of electrophiles work best for michael reactions

A

work best when the electrophile is an a,b-unsaturated compound

39
Q

T or F: all electrophiles for michael reactions are carbonyls

A

false; they don’t have to be carbonyls, but they must have resonance

40
Q

T or F: enamines are stabilized enolates (michael donors)

A

true

41
Q

since enamines are stabilized enolates (michael donors), what can they do?

A

they can attack a,b-unsaturated compounds (michael acceptors) to produce an iminium salt

42
Q

what will we have to do to the iminium salt produced from the enamine in the michael reaction

A

quench it because it’s a salt (aka hydrolysis)

43
Q

what happens when an iminium salt is hydrolyzed

A

it reverts to a ketone

44
Q

what is stork enamine alkylation

A

making use of an enamine to perform 1,4-addition

45
Q

why would we do stork over michael

A

enolates tend to be poor michael donors, so enamines are better to do the reaction (the products of both will be the same, but the yields and # of side products will differ)

CHEM 2420- organic chem 2 (10 decks)

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