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CHEM 2420- organic chem 2 > Ketones and aldehydes > Flashcards

Ketones and aldehydes Flashcards

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1
Q

what is a carbonyl group

A

C=O

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2
Q

what is an acyl group

A

a carbonyl group (C=O) bonded to a carbon group

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3
Q

what is a ketone

A

C=O bonded to two R groups

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4
Q

what suffix do ketones have

A

-one

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5
Q

when is “oxo” used for ketones

A

oxo describes the =O (the oxygen group)

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6
Q

what is an aldehyde

A

C=O bonded to an R group and an H

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7
Q

what suffix do aldehydes use

A

-al

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8
Q

when is “oxo” used for aldehydes

A

oxo describes the =O (the oxygen group)

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9
Q

what prefix do aldehydes use

A

formyl-

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10
Q

what shape does the C=O bond have

A

trigonal planar, sp2

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11
Q

describe the bond strength and length of the C=O bond

A

the C=O bonds are stronger but shorter than the typical sigma bond

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12
Q

T or F: the C=O bond has a dipole moment (explain)

A

true; C is electron poor while O is electron rich, and O pulls electron density towards it giving it a partial neg charge

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13
Q

what can IRs tell us about our molecule (in regards to the C=O)

A

it can show if C=O is present. We won’t know where or how many though

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14
Q

what can HNMR tell us about our molecule

A

the singlet’s position is what’s indicative of an aldehyde vs carboxylic acid

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15
Q

what does CNMR tell us about our molecule

A

carbonyls in a C13 NMR will stand out, near the 113 area (far left)

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16
Q

how do we prepare acids or ketones

A

oxidize an alcohol

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17
Q

what is the product when a 1 degree alcohol is oxidized

A

carboxylic acid

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18
Q

what is the product when a 2 degree alcohol is oxidized

A

ketone

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19
Q

what is the product when a 3 degree alcohol is oxidized

A

no reaction

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20
Q

what are some examples of things that go over the arrow in an oxidation reaction

A
  • KMno4
  • H+ and K2Cr2O3
  • H+ and Na2Cr2O3
  • H2Cr2O3
  • CrO3 and heat (Jones)
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21
Q

what do you do if you want to oxidize a 1 degree alcohol into an aldehyde instead of an acid?

A

for a milder reaction you use PCC. It stops the reaction at an aldehyde

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22
Q

what is ozonolysis of alkenes (what is the reactant and product)

A

turns an alkene into a carbonyl (we get two of these products)

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23
Q

what happens in ozonolysis of alkenes

A

we split the double bond and make 2 of our products. Oxidation is happening on both sides

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24
Q

T or F: in ozonolysis of alkenes, if the reactant was asymmetrical we would get the same 2 products

A

false, an asymmetrical alkene would mean we get 2 different products

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25
Q

what is hydration of alkynes

A

turns an alkyne into a carbonyl

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26
Q

what happens in hydration of alkynes

A

we use acidified water with mercury as a salt. We’re doing oxidation of the carbon up to an alcohol, but we will continue to oxidize it all the way up to a carbonyl

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27
Q

what is reduction of esters to aldehydes

A

ester is reduced to an aldehyde

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28
Q

what happens when esters are reduced to aldehydes

A

we use DIBAL washed with acid to do this

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29
Q

what is reduction of nitriles

A

a nitrile (R-C-(triple bond)-N) is reduced into an aldehyde

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30
Q

what happens when nitriles are reduced

A

use DIBAL washed with acid

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31
Q

what is reduction of acyl halides

A

an acyl halide (C=O bonded to R and X) is reduced into an aldehyde + LiX

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32
Q

what happens in reduction of acyl halides

A

we use LiAIH4 (Or some other variation of LiAl). It is bulky

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33
Q

what are the different types of nucleophiles (5)

A

H-type, O-type, S-type, N-type, and C-type

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34
Q

T or F: H- is a nucleophile

A

false; it’s a strong base

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35
Q

since H- is a strong base and not a nucleophile, what do we use as our nucleophile

A

we use NaBH4 (think of it as BH3 and a hydride)

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36
Q

why do we use boron in the nucleophile for H-type nucleophiles

A

it’s not very large or polarizable, making the nucleophile selective

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37
Q

after H-type nucleophiles react and make a product, why do we get stuck

A

we get stuck because in order for the product to reform, it has to kick off either C or H, and none are good options

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38
Q

in H-type reactions, we get stuck at the product so how do we combat this, and what are we left with

A

we QUENCH the reaction. Use water or a dilute acid. this increases the amount of protons added to the reaction –> result is an alcohol

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39
Q

to show the overall carbonyl group reaction, is it in one step or two? what is it/are they? why?

A

2 steps, 1= reaction with LAH, 2=reaction with water. In two steps because LAH reacts violently with water. Product=enantiomers

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40
Q

to show the overall H-type reaction, is it in one step or two? what is it/are they? why?

A

it’s in 1 step because NaBH4 is more mild. The reaction is essentially the reverse of the oxidization of the alcohol

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41
Q

what is an O-type nucleophile

A

a nucleophile with oxygen

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42
Q

does an O-type nucleophile have a slower or faster attack than H-type? why?

A

slower attack than H; due to electron density

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43
Q

what is wrong with the product of an O-type reaction

A

it has a very good leaving group which will just leave

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44
Q

since the product of o-type has a leaving group that will leave, what can we do

A

we can either reverse to the starting materials or make the carbonyl group more electrophilic

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45
Q

in o-type, how do we make the carbon electrophilic

A

we use a catalytic amount of protons or do the reaction in acidic conditions

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46
Q

after making the carbon more electrophilic in o-type, what is the product and what is the outcome of this

A

positively charged oxygen on the product, so it will want the nucleophile

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47
Q

T or F: making the carbon more electrophilic in the o-type reaction is reversible

A

true; so we must use equilibrium arrows

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48
Q

describe the steps of the o-type reaction

A
  • adding catalytic hydrogen to make the electrophilic carbon
  • alcohol nucleophile attacks, product has a good LG
  • a proton is lost (we get an X shaped product) and protonation occurs to get water as an LG
  • water leaves, nucleophile attacks again, deprotonation occurs
  • we’re left with a ketal or an acetal
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49
Q

what is the difference between a ketal and an acetal

A

ketal: two ethers that form from the original carbonyl
acetal: same as ketal but has an H group and an R instead of 2 R’s (comes from aldehyde)

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50
Q

in o-type, how can we drive the equilibrium towards a product

A

remove water will shift the reaction to the right

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51
Q

where in the o-type mechanism do we want to remove water to drive the reaction forward

A

in the 5th step:

  • our reactant is X shaped and one of the subs is positively charged water
  • we can remove water, which gives us a ketone bonded to an R
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52
Q

in o-type, what do we use to remove water

A

we use azeotropic distillation glassware – a dean-stark trap

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53
Q

how does a dean-stark trap work?

A

water is separated from the reaction mixture via differences in density and miscibility. water is trapped and doesn’t return to the reaction

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54
Q

T or F: in o-type reactions, the stoichiometry of any alcohol we use is important

A

true;

55
Q

what do we do if we only want to react with one of the subs on a molecule, and leave the other alone?

A

we need to use a diol as a protecting group

56
Q

why are protecting groups useful?

A

if we want to react the less reactive sub on a molecule, the protecting group protects the one we want to keep

57
Q

describe the mechanism of adding a protecting group. The reactant has a ketone we want to keep and an ester we want to reduce

A

the protecting group protects the ketone, and then we add a reducing agent and then water, making the ester into an alcohol. Then we wash with acidified water to convert it back into a ketone

58
Q

describe the hydration of carbonyls to diols

A
  • can happen under acidic or basic conditions

- the carbonyl can react with either H+ or OH- and water, producing a geminal diol (X shaped, with two OH groups)

59
Q

T or F: a more electron deficient carbonyl = a slower reaction rate. Explain

A

false; a more electron deficient carbonyl = faster reaction rate
- if the carbon is electron rich, the nucleophile won’t want to attack it, so the carbon must be electron poor

60
Q

what is the purpose of using S-type nucleophiles

A

used as tools to grow carbon chains by making a new C-C bond

61
Q

what is used in s-type reactions?

A

start with an aldehyde, use dimercaptoethane and a lewis acid, product is a thioacetal

62
Q

what are the reagent and product in s-type reactions

A

start with an aldehyde, end with a thioacetal

63
Q

what is a thioacetal

A

a ketal, but instead of O we have S

64
Q

in s-type reactions, why do we use a lewis acid

A

the lewis acid makes the carbonyl group more electrophilic than H+

65
Q

in s-type, why do we want the lewis acid to make the carbonyl group more electrophilic than H+

A

then a strong base will deprotonate the thioacetal, because that H is going to experience a conjugate base that is stabilized

66
Q

T or F: in s-type, we need a very strong base to remove the proton

A

true

67
Q

in s-type, after the mechanism stuff, we’re left with a carbon nucleophile. What can we do now?

A

we can treat it with any of the substitutions we saw last semester

68
Q

in s-type, what happens when we treat the carbon nucleophile with an alkyl halide?

A

the reaction creates a new C-C bond, and allows us to grow our carbon chain

69
Q

in s-type, once we react the carbon nucleophile with an alkyl halide and create the new c-c bond, what two things can we do to remove the thioacetal

A

hydrolysis or desulfurization

70
Q

describe hydrolysis to remove thioacetals

A

converts thioacetal to a ketone. Can be under acidic or basic conditions

71
Q

describe desulfurization to remove a thioacetal

A

used when we don’t want acidic or basic conditions (it’s hydrogenation)
- converts thioacetal to a hydrocarbon chain with an R group

72
Q

describe n-type reactions

A

carbonyl is treated with amines and water is removed, producing a product containing C and N (depends on what type of amine is used)

73
Q

what is the product when a 1o amine is used

A

imine. R-N=C, with a lone pair on the N

74
Q

T or F: 1o amine to produce an imine uses the same pathway that was used to produce a ketal

A

true

75
Q

T or F: we get a mixture of products of imines if our starting materials are unsymmetrical

A

true

76
Q

for finding the major product of imines, what do we need to consider

A

sterics between the R groups and the rest of the molecule

77
Q

in n-type, what is our product when we use a 2o amine

A

an enamine. It’s an amine bonded to a vinyl carbon. Has 2 R groups from the N and a lone pair

78
Q

what is special about the mechanism of 2o amine to enamine

A

similar steps to imine mechanism, except the secondary amine acts as a base instead of water to deprotonate

79
Q

which carbon is deprotonated in a 2o amine reaction (n-type)

A

the alpha carbon (carbon next to the carbon of the double bond)

80
Q

T or F: if our starting material is asymmetrical, we get a mixture of products in our 2o amine n-type reaction

A

true

81
Q

in 2o amine –> enamine reaction, which product is our major product

A

the less substituted double bond is the major product

82
Q

describe the clemmensen reduction

A

carbonyl treated under very acidic conditions to create a hydrocarbon

83
Q

if we don’t want to use the harsh clemmensen reduction reaction, what can we do instead?

A

use hydrazine to convert the carbonyl group into a hydrazone

84
Q

what is hydrazine

A

N2H4

it’s N-N, where each N is bonded to 2 H’s and has a lone pair

85
Q

what is hydrazone

A

H2N-N(with lone pair)=C(joined to the rest of the molecule)

86
Q

what is the wolff-kishner reaction

A

reduction of a hydrozone. Performed under basic conditions, and N2 gas is produced

87
Q

what is the driving force of wolff-kishner reactions

A

N2 gas production (irreversible)

88
Q

what is the product of a wolff-kishner reaction

A

a fully reduced product from a carbonyl down to a straight chain

89
Q

describe C-

A

acts as a strong base and is one of the strongest bases we have

90
Q

what is an example of a C-type nucleophile (ie how might C- be written)

A

as BuLi (Bu=butane that’s negatively charged around Li+)

91
Q

what can C- do since it’s negatively charged

A

it wants to deprotonate anything it can (ie water to create OH)

92
Q

T or F: C- acts like a nucleophile

A

false, it’s so strong that it acts like a base

93
Q

for C-type nucleophile questions, what will the C- be attached to

A

an organic species

94
Q

describe the mechanism of a C-type reaction

A

C nucleophile attacks the carbonyl from the bottom, causing electrons from the double bond to go to the O (=X shaped product). Then, the electrons from the O attack the HX nucleophile, to create a cyanohydrin

95
Q

name the product of C-type reactions

A

cyanohydrin

96
Q

what’s the purpose of grignard reactions

A

insertion of magnesium (or lithium) into an alkyl halide

97
Q

describe how polarization is affected in a grignard reaction

A

polarization is revsered when Mg is added into the molecule. This is because the carbon is more electron dense than Mg

98
Q

prior to the grignard reaction, describe the dipole moment

A

partial positive carbon, partial negative X

99
Q

after the grignard reaction, describe the dipole moment

A

partial negative carbon, partial positive Mg

100
Q

what is X in the grignard reaction

A

we don’t use F much, so X=I, Cl, or Br

101
Q

what are the conditions for a successful grignard reaction

A
  • must be a polar aprotic solvent (ie Et2O)

- no water or alcohols! (because protons destroy the reagent RMgX)

102
Q

what can we make with the grignard reagent (RMgX)

A

an alcohol

103
Q

describe the process of using RMgX to make an alcohol

A

RMgX reactions with a carbonyl and an aprotic solvent, to make an X shaped molecule with a neg/ O. Then we quench it with water, making an alcohol

104
Q

T or F: grignard reagents (RMgX) can be 1o, 2o, or 3o

A

true

105
Q

which carbons make up the new c-c bond in the product of the grignard mechanism

A

the nucleophilic to the electrophilic carbon

106
Q

what is the purpose of the wittig reaction

A

we want a new c-c bond, but not an alcohol like we saw with grignard

107
Q

what molecule does the wittig start with

A

starts with triphenylphosphine; P(Ph)3

108
Q

what is the formula of triphenylphosphine

A

P(Ph)3

109
Q

describe triphenylphosphine

A

a phosphate with 3 phenyl groups (benzene rings) attached, and it has a lone electron pair. It’s bulky

110
Q

what is the reagent of the wittig reaction

A

an alkyl halide

111
Q

describe the mechanism of the wittig reaction

A

P(Ph)3 reacts with the alkyl halide via backside attack (Sn2), causing the leaving group X to leave. P(Ph)3 is now attached, and P has a positive charge. This is an intermediate.
Next, BuLi (strong base) deprotonates the carbon, which produces an YLIDE. Then we get hybrid resonance structures. Then the molecule attacks a carbonyl from the bottom, we get an X shaped molecule, it cyclizes, it rearranges, and we’re left with an alkene (new c-c bond was made) and P(Ph)3O

112
Q

what is an YLIDE

A

a compound with a C- bonded to a P+, S+, N+, etc

113
Q

T or F: wittig reaction produces a new c-c bond

A

true

114
Q

in the wittig reaction, which carbons make up the new c-c bond

A

carbon of the carbonyl to the electropositive carbon of the alkyl halide

115
Q

what is the result of the wittig reaction if you start with unsymmetrical starting material

A

a mixture of products

116
Q

what happens to the wittig product when it’s oxidized

A

it reverts back to the original carbonyl

117
Q

what are two “one-pot” reactions

A

cannizzaro and baeyer-villager

118
Q

what is the starting material in the cannizzaro reaction

A

aldehyde

119
Q

what is/are the products of the cannizzaro reaction

A

an alcohol and an acid

120
Q

in what proportions are the cannizzaro products made

A

50/50

121
Q

what are the 3 downfalls of the cannizzaro reaction

A
  • only used for aldehydes
  • the aldehydes must lack alpha hydrogens
  • can only be done in basic conditions
122
Q

in the cannizzaro reaction, does the OH- act as a nucleophile or a base

A

nucleophile, because we don’t have the conditions to deprotonate

123
Q

describe the cannizzaro reaction mechanism

A

OH- attacks the aldehyde from the bottom, electrons move to make O-. We now have an X shaped intermediate with O-, H, OH, and Ph. The electrons then move away from the O-, the H leaves, and it bottom attacks the starting material (which then can react with water), creating 2 products

124
Q

what is the baeyer-villager reaction

A

oxidation using per-acids (inserts an oxygen beside the carbonyl)

125
Q

what are per-acids

A

carboxylic acid, but instead of OH we have an additional oxygen in there

126
Q

what is the product of the baeyer-villager reaction

A

ester

127
Q

what do we use to perform the baeyer-villager reaction

A

mCPBA

  • benzene ring with Cl attached
  • also has the per-acid attached
128
Q

why is mCPBA used

A

it’s only mildly acidic (good because we aren’t using it for acidity), and it’s safer than other peroxides

129
Q

describe the baeyer-villager mechanism

A

mCPBA is not a nucleophile, so the O of the carbonyl deprotonates it, giving it a neg charge=nucleophile. Nuc attacks, then we get intramolecular cyclization (concerted), then we get an alkyl shift of the R group = ester

130
Q

describe the product of the baeyer-villager reaction if the starting material is symmetrical

A

you get one product

131
Q

describe the product of the baeyer-villager reaction if the starting material is unsymmetrical

A

you have two products, but the yield is NOT 50/50

132
Q

T or F: the products of the baeyer-villager reaction (if there’s 2) are always 50/50

A

FALSE

133
Q

how do you determine the major product of the baeyer-villager reaction

A

there’s precedence of R group migration.
H>3>2>Ph>methide>1

compare the R groups of each product (R group is the one attached to the oxygen)

CHEM 2420- organic chem 2 (10 decks)

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