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Organic Chemistry II > Ch.22 > Flashcards

Ch.22 Flashcards

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1
Q

What is alpha substitution?

A

the substitution of one of the hydrogens attached to the alpha carbon for an electrophile

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2
Q

Alpha substitution occurs through an _____ ion intermediate.

A

enolate

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3
Q

What is tautomerization?

A

an interconversion of isomers that occurs through the migration of a proton and the movement of a double bond

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4
Q

Are tautomers resonance forms?

A

no

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5
Q

Describe base-catalyzed tautomerism.

A

A proton on the a carbon is abstracted to form a resonance-stabilized enolate ion with the negative charge spread over a carbon atom and an oxygen atom

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6
Q

Equilibrium in base-catalyzed tautomerism favors which form?

A

favors keto form over the enolate ion

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7
Q

Describe acid-catalyzed tautomerism.

A

the oxygen is first protonated, and then a proton from the a carbon is removed

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8
Q

Describe reacemization.

A

If a chiral a carbon has an enolizable hydrogen atom, a trace of acid or base allows that carbon to invert its configuration, with the enol serving as the intermediate.

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9
Q

What is the pKa for alpha H of aldehyde or ketone?

A

around 20

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10
Q

Which is more acidic, and aldehyde/ketone or alkane/alkene?

A

aldehyde/ketone

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11
Q

What is the approximate pKa of water?

A

15.7

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12
Q

what is the pKa of an alkyne?

A

25

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13
Q

what is the pKa of an alcohol?

A

16-19

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14
Q

Even though the keto–enol tautomerism equilibrium favors the keto form, addition of an ______ ______ the equilibrium toward the formation of more enol

A

electrophile shifts

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15
Q

How is LDA made?

A

by using an alkyllitium reagent to deprotonate diispropylamine

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16
Q

What can LDA do?

A

convert a carbonyl compound completely to its enolate

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17
Q

what happens when LDA reacts with a ketone?

A

it abstracts the a proton to form the lithium salt of the enolate

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18
Q

Ketones or aldehydes react with a secondary amine to form _________.

A

enamines

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19
Q

The enamine has a nucleophilic a carbon, which can be used to attack ___________.

A

electrophiles

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20
Q

The electrostatic potential map (EPM) of a simple enamine shows a what (red) near the a carbon atom of the double bond?

A

high negative electrostatic potential

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21
Q

Enamines displace halides from reactive alkyl halides, giving alkylated _____ __________.

A

iminium salts

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22
Q

The alkylated iminium salt can be hydrolyzed to the ketone under _____ conditions.

A

acidic

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23
Q

Hydrolysis of the iminium salt produces the ______ as the final product.

A

beta-diketone

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24
Q

When a ketone is treated with a halogen and a base, an ____________ reaction occurs.

A

alpha halogenation

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25
Q

What reaction is called base-promoted?

A

the alpha halogenation of ketone

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26
Q

In multiple halogenation, which halogenation occurs faster?

A

second halogenation

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27
Q

In haloform reaction, when Cl2 is used, what is formed?

A

chloroform

28
Q

In haloform reaction, when Br2 is used, what is formed?

A

bromoform

29
Q

In haloform reaction, when I2 is used, what is formed?

A

iodoform

30
Q

What is the iodoform test used to identify?

A

methyl ketones (or secondary alcohols)

31
Q

Alcohols can give a _____ iodoform test.

A

positive

32
Q

What is iodoform (CHI3)?

A

a yellow solid that participates out of solution

33
Q

The _____ reaction replaces a hydrogen atom with a bromine atom on the a carbon of a carboxylic acid (a-bromoacid).

A

HVZ

34
Q

what do condensations do?

A

combine two or more molecules, often with the loss of a small molecule such as water or an alcohol

35
Q

what is the aldol condensation?

A

the addition of an enolate ion to another carbonyl group. It occurs under basic conditions

36
Q

In aldol condensations, When the reaction is carried out at _____ temperatures, the beta-hydroxy carbonyl compound can be isolated

A

low

37
Q

In aldol condensation, what will heating do?

A

Heating will dehydrate the aldol product to the alpha,beta-unsaturated compound.

38
Q

what is crossed aldol condensation?

A

When the enolate of one aldehyde (or ketone) adds to the carbonyl group of a different aldehyde or ketone

39
Q

Intramolecular aldol reactions of diketones are often used for making what?

A

five- and six-membered rings

40
Q

Is stereo control possible for Mukaiyama Aldol Addition and Alkylation?

A

yes

41
Q

Is stereo control possible for Henry Reaction?

A

yes

42
Q

Describe the mannich reaction.

A

formation of the iminium ion of aldehyde

43
Q

The claisen condensation results when what happens?

A

when an ester molecule undergoes nucleophilic acyl substitution by an enolate

44
Q

What is an internal Claisen cyclization is called?

A

a Dieckmann condensation or a Dieckmann cyclization

45
Q

What are useful esters?

A

benzoates, formates, carbonates, and oxalates

46
Q

_________ may also react with an ester to form a beta-diketone.

A

ketones

47
Q

What happens in a crossed claisen condensation?

A

an ester without alpha hydrogens serves as the electrophilic component

48
Q

Which are more acidic, and more likely to deprotonate and serve as the enolate component in the condensation, ketones or esters?

A

ketones

49
Q

What does malonic ester synthesis make?

A

substituted derivatives of acetic acids.

50
Q

______ takes place through a cyclic transition state, initially giving an enol form that quickly tautomerizes to the product.

A

Decarboxylation

51
Q

What are the final products of acetoacetic ester synthesis?

A

ketones

52
Q

_____ ion completely deprotonates acetoacetic ester.

A

Ethoxide

53
Q

alpha,beta-Unsaturated carbonyl compounds have unusually _______ double bonds.

A

electrophilic

54
Q

describe hard nucleophiles.

A

have low energy HOMO’s and a high charge + have high energy LUMO’s and a high charge

55
Q

describe soft nucleophiles.

A

have high energy HOMO’s and are polarizable + low energy LUMO’s and are polarizable

56
Q

What dominates the reactivity of hard nucleophiles?

A

charge

57
Q

What dominates the reactivity of soft nucleophiles?

A

orbital interactions

58
Q

Hard nucleophiles tend to react well with ___ electrophiles.

A

hard

59
Q

Soft electrophiles tend to react well with ____ nucleophiles.

A

soft

60
Q

What are some hard basic nucleophiles?

A

H20, HO-, RCO2-, Cl-, ROH, RO-, NH3, RNH2

61
Q

What are some hard acidic electrophiles?

A

H+, Li+, Na+, K+, Mg2+, BF3

62
Q

What are some soft basic nucleophiles?

A

I-, RS-, RSe-, S2-, RSH, RSR, R3P, alkenes, aromatics, R-

63
Q

What are some soft acidic electrophiles?

A

Ag+, Pd2+, I2, Br2, radicals

64
Q

An enolate will do a ___,___-attack on the a,b-unsaturated ketone (MVK).

A

1,4

65
Q

Describe robinson annulation.

A

With enough base, the product of the Michael reaction undergoes a spontaneous intramolecular aldol condensation, usually with dehydration, to give a six-membered ring—a conjugated cyclohexenone

Organic Chemistry II (8 decks)

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