Carboxylic acids Flashcards

1
Q

Carboxylic acid

A

COOH (image)

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2
Q

Carboxylic acids are

A

Dimeric

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3
Q

Dimeric

A

Consisting of two similar molecules that have been linked together

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4
Q

Low Pka

A

strong acid

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5
Q

high pka

A

weak acid

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6
Q

strength of alkanes as an acid

A

very weak acid

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7
Q

are carboxylic acids strong or weak acids

A

most are weak acids

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8
Q

pKa table

A

draw table out

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9
Q

electronegativity

A

a measure of the ability of an atom in a chemical compound to attract electrons

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10
Q

inductive effects

A

stabilize charge through sigma bonds

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11
Q

electron-withdrawing substituents increase

A

acidity of nearby atom

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12
Q

electron withdrawing groups effect increases with ____ and decreases with ______

A

electronegativity, distance

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13
Q

Rank chlorine, iodine, fluorine and bromine in order of increasing electronegativity

A

F > Cl > Br > I

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14
Q

A carboxylic acid with F as a substituent is ___ acidic than one without

A

more

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15
Q

two methods of preparing carboxylic acids

A

1) oxidation in aqueous conditions 2) addition of Grignard or alkyl lithium reagents to CO2

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16
Q

carboxylic acids ____ undergo nucleophilic substitution with negatively charged nucleophiles

A

do NOT

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17
Q

LiAlH4 will reduce _____ to _____

A

carboxylic acids, primary alcohols

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18
Q

reduction using LiAlH4

A

1) deprotonation
2) addition of hydride
3) elimination
4) addition of hydride
5) protonation

(Image)

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19
Q

Acid chloride

A

Image

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20
Q

Anhydride

A

Image

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21
Q

Ester

A

Image

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22
Q

Amide

A

Image

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23
Q

Nucleophilic substitution

A

A type of substitution reaction in which a nucleophile is attracted to an electron-deficient centre or atom, where it donates a pair of electrons to form a new covalent bond.

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24
Q

Addition elimination mechanism

A

1) add to carbonyl
2) elimination of leaving group

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25
Q

Nucleophilic acyl substitution

A

1) Nucleophilic addition
2) elimination of the leaving group and reformation of the carbonyl (Image)

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26
Q

Golden rule of acid base reactions

A

stronger acids and stronger base should react to give a weaker acid and a weaker base

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27
Q

Four derivatives ranked by reactivity

A

Acid Chloride > anhydride > ester > amide

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28
Q

Two nucleophilic acyl substitutions that don’t work

A

Anhydride into acid chloride ester into anhydride

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29
Q

Conversion of carboxylic acids to acid halides

A

1) chloride is a bad nucleophile
2) leaving group must be worse than chloride
3) leaving group disintegrates making the reaction irreversible
4) requires SOCl2, HCl, and SO2 gas

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30
Q

Mechanism of carboxylic acids to acid halides

A

1) attack on thionyl chloride
2) additon of Cl- to carbonyl carbon
3) elimination of SO2Cl
4) deprotonation

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31
Q

Reaction of carboxylic acid with alcohols to make esters

A

Requires an acid catalyst (H2SO4) and an alcohol

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32
Q

Esterfication

A

The reaction of an alcohol with a carboxylic acid to produce an ester and water (Image)

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33
Q

Using an excess of alcohol drives the esterification equilibrium towards the

A

Ester product

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34
Q

Equal concentrations of alcohol and acid

A

65% ester

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35
Q

10 fold excess of alcohol to acid

A

97% ester

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36
Q

100 fold excess of alcohol to acid

A

99% ester

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37
Q

Mechanism of esterfication

A

Image

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38
Q

Backwards reaction of esterfication

A

Hydrolysis

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39
Q

Mechanism of hydrolysis

A

Image

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40
Q

Ester hydrolysis is best done under ____ conditions

A

basic

41
Q

Amides are the product of a net condensation reaction between a

A

carboxylic acid and an amine

42
Q

Consequence of partial double bond character

A

Restricted rotation

43
Q

For amides, interconversion of conformers is slow due to

A

significant double bond character of C-N bond

44
Q

Amides react with acid at the

A

Oxygen

45
Q

Amine N-H bonds are less acidic than

A

Amide N-H bonds

46
Q

Brute force method of amide synthesis from acids

A

Wrong method. Carboxylic acids and amines form salts through acid base reactions

47
Q

Pyrolysis

A

The decomposition of organic matter by heat

48
Q

Right way to prepare amides from acids

A

Combination of amines and carboxylic acids int he presence of a dehydrating reagent such as DCC

49
Q

DCC

A

Image

50
Q

Mechanism of preparing amines from carboxylic acids

A

1) deprotonation of acid
2) attack on DCC
3) addition
4) proton transfer
5)elimination

51
Q

Basic hydrolysis of amides requires

A

Strong base and heat

52
Q

Mechanism of basic amide hydrolysis

A

1) Addition
2) Elimination
3) Deprotonation

53
Q

Lactams

A

cyclic amides

54
Q

Best condones for hydrolysis of amides

A

Acidic conditions, need more mild conditions than the conditions required for basic conditions

55
Q

Mechanism of acid hydrolysis of amide

A

Image

56
Q

What explains high reactivity

A

Resonance forms

57
Q

Non aromatic compounds are ____ reactive than aromatic compounds

A

More

58
Q

Strecker reaction

A

Image

59
Q

Hydrolysis of nitriles to carboxylic acids requires

A

Aqueous acid

60
Q

Mechanism of nitrile hydrolysis

A

Image

61
Q

Under gentle reaction conditions, the hydrolysis of nitriles stops at

A

the amide

62
Q

In acyl halide reactivity _____ loses every time

A

Chloride

63
Q

Features of lithium tri-t-butoxy aluminium hydride

A
  • less reactive than LiAlH4
  • cannot reduce carboxylic acids
  • Use of one equivalent reduces acid chlorides to aldehydes
    -Catalytic hydrogenation also works
64
Q

Reduction of acyl halides

A

Image

65
Q

Mechanism of reception of acid halides

A

1) addition of hydride
2) elimination of halides
3) deprotonation
4) acid workup

66
Q

Hydrolysis of esters under basic conditions requires

A

NaOH and acid workup

67
Q

Mechanism of ester hydrolysis

A

Image

68
Q

Cyclic esters can undergo

A

basic hydrolysis

69
Q

Saponification

A

the reaction between a fat and a strong base to produce glycerol and the salt of a fatty acid (soap)

70
Q

Transesterification

A

The process that transforms one ester to another when an alcohol acts as a nucleophile and displaces the alkoxy group on an ester.
(Image)

71
Q

Mechanism of transesterfication under acidic conditions

A

1) protonation
2) addition
3) deprotonation
4) protonation
5) elimination
6) deprotonation

72
Q

Mechanism of transesterfication

A

1) nucleophilic addition
2) elimination

73
Q

Facts about acidic transesterfication

A

All steps in equilibrium
equilibrium favours whichever alcohol is present in greater concentration

74
Q

Lactone

A

Image

75
Q

DiBal

A

Image
Ester to aldehyde

76
Q

Mechanism of reduction of esters to aldehydes using DiBal

A

1) Coordination of oxygen to Lewis acid aluminium
2) addition of hydride
3) addition of mild acid workup with warming

77
Q

Reduction of nitriles with DIBal

A

Image

78
Q

Why is an Al-O bond so strong

A

Electronegativity and charge differences

79
Q

Mechanism reduction of amides to amines using LiAlH4

A

1) addition of hydride
2) elimination
3) addition of hydride
image

80
Q

Mechanism of reduction of nitriles to primary amines with LiALH4

A

1) addition to nitrile
2) addition to C=N
3) mild acid workup

81
Q

factors associated with acidity

A

inductive effects
resonance delocalization
electronegativity of neighbouring groups

82
Q

esters are ___ than aldehydes or ketones

A

less

83
Q

enolates are most nucleophilic at

A

carbon

84
Q

enolate

A

intermediate
stabilized by resonance
enol+ base—– enolate

85
Q

where does the negative charge on enolate sit

A

the oxygen

86
Q

enolate formation requires the C-H bond align parallel to

A

carbonyl bond

87
Q

enolizable

A

must have a C-H on the alpha carbon

88
Q

keto-enol tautomerism via enolates

A

Break C-H
Form O-H
Break C-O
Form C-C
Form O-H

89
Q

Deuterium labeling

A

Image

90
Q

Racemate

A

a mixture containig equal amounts of two enantiomers

91
Q

Chiral centres on enolates alpha carbons undergo

A

racemization

92
Q

Cause of racemates

A

addition is able to occur at the top and bottom of the attack site

93
Q

Chiral

A

a molecule that is not superimposable on its mirror image

94
Q

epimerzation

A

the reversible interconversion of epimers

95
Q

Epimer

A

Diasteromers that differ at only one chiral centre
Imgae

96
Q

When do epimers occur

A

When the alpha carbon is chiral and there is more than one chiral centre and it is treated with a base

97
Q

Facts about halogenation of enolates

A

Non selective under basic conditions
hard to control under basic conditions
multiple halogenation can occur

98
Q

acid catalyzed halogenation of ketones

A

can halogenate only one or two a-H’s
use acetic acid as solvent and catalyst Image

99
Q

Halogenation of enolates

A

Image