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AQA A Level Organic Chemistry > 9. Carboxylic Acids and Derivatives > Flashcards

9. Carboxylic Acids and Derivatives Flashcards

1
Q

What is the functional group of carboxylic acids?

A

R - COOH

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2
Q

Are carboxylic acids weak or strong acids?

A

Weak

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3
Q

Why do carboxylic acids not fully dissociate in water?

A

As they are weak acids

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4
Q

What equations can be used to show how carboxylic acids do not fully dissociate in water?

A
  • R-COOH + H2O ⇋ RCOO- + H3O⁺

* R-COOH ⇋ R-COO- + H⁺

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5
Q

How is a proton released in the equation R-COOH ⇋ R-COO- + H⁺?

A

The polarised C=O group attracts electrons away from the O-H group, weakening the OH bond enabling the proton to be released

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6
Q

Why do carboxylic acids dissociate in water, but alcohols do not?

A

In the carboxylic acid OH group the C=O group attracts electrons away, weakening the OH bond so a proton can be released - but there is no C=O group in an alcohol so there is nothing to weaken the OH bond

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7
Q

What are carboxylic acids produced by?

A

The oxidation of primary alcohols or aldehydes

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8
Q

What happens when ethanol is exposed to air?

A

It oxidises to ethanoic acid

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9
Q

Why can wine taste vinegary if left open?

A

The ethanol oxidises to ethanoic acid

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10
Q

Where is methanoic acid found naturally?

A

In an ant bite; it can cause irritation

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11
Q

Where is ethanedioic acid found naturally?

A

As a metal salt in rhubarb and gives it a sour taste

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12
Q

What is ethanedioic acid?

A

A poisonous white crystalline solid

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13
Q

Where is benzene carboxylic acid (benzoic acid) found?

A

Raspberries and some tree barks

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14
Q

How is benzoic acid used?

A

As a preservative and an antioxidant in numerous foods

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15
Q

How are carboxylic acids named?

A

Using the suffix -oic acid

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16
Q

What do carboxylic acids react with alkalis to form?

A

Water and carboxylate salts

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17
Q

In the reaction of carboxylic acids with alkalis, what happens in terms of hydrogen ions?

A

The acid donates a hydrogen ion (from -COOH) which is replaced by the metal in the alkali

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18
Q

Equation for ethanoic acid with sodium hydroxide?

A

CH3COOH + NaOH → CH3COONa + H2O

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19
Q

In the products from carboxylic acids with alkalis, what is the nature of the bond between the carboxylate ion and the metal?

A

Ionic

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20
Q

How are carboxylate salts named?

A

The prefix is the name of the metal and the suffix is -oate instead of -oic acid

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21
Q

What do carboxylic acids react with carbonates and hydrogen carbonates to form?

A

Salt, water and carbon dioxide

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22
Q

Are carbonates and hydrogen carbonates weak or strong bases?

A

Weak

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23
Q

What is a general equation for the reaction of carboxylic acids with sodium carbonates?

A

R-COOH + Na2CO3 → RCOO⁻⁻Na⁺ + CO2 + H2O

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24
Q

What is a general equation for the reaction of carboxylic acids with sodium hydrogencarbonates?

A

R-COOH + NaHCO3 → RCOO⁻⁻Na⁺ + CO2 + H2O

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25
Q

How does carboxylic acids being weak acids affect the rate of reaction with carbonates/hydrogen carbonates?

A

The reaction rate is slower than strong acids (e.g. HCl, H2SO4) - however still sufficient to produce CO2

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26
Q

In the reaction of carboxylic acids and carbonates/hydrogen carbonates, how can it be confirmed that the reactant is a carboxylic acid?

A

Presence of CO2 can be confirmed by passing gas through limewater

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27
Q

Describe the equipment used to test for carboxylic acids

A

A test tube containing HCl and calcium carbonate with a bung over the top attached via delivery tube to a test tube collecting CO2 in limewater

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28
Q

What do carboxylic acids react with alcohols to form?

A

An ester and water

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29
Q

What must be present for carboxylic acids to react with alcohols?

A

Concentrated sulphuric acid

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30
Q

What is esterification?

A

When carboxylic acids react with alcohols in the presence of concentrated sulphuric acid

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31
Q

What do methanol and ethanoic acid react to form?

A

Methyl ethanoate

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32
Q

What does the H2SO4 act as in esterification?

A

A catalyst

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33
Q

What conditions is esterification carried out under?

A

Under reflux

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34
Q

When are esters produced?

A

In the reaction between carboxylic acids and alcohols

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35
Q

What is the functional group for esters?

A

R1 - COO - R2

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36
Q

What are the names of esters based on?

A

The carboxylic acid and alcohol from which they are produced

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37
Q

What is the first component of the ester name derived from?

A

The number of carbons in the alcohol (ending with -yl)

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38
Q

What is the second component of the ester name derived from?

A

The number of carbons in the carboxylic acid (ending with -oate)

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39
Q

What reactants make methyl propanoate?

A

Methanol and propanoic acid

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40
Q

What is the reverse of esterification?

A

Hydrolysis of esters

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41
Q

What is the hydrolysis of esters?

A

The reverse of esterfication

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42
Q

What is produced in the hydrolysis of esters?

A

An acid and an alcohol

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43
Q

Why is hydrolysis of esters possible?

A

The carbonyl C is susceptible to nucleophilic attack

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44
Q

What does hydrolysis of esters involve, considering that esterification involves the removal of a water molecule?

A

The addition of a water molecule

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45
Q

What is the removal of a water molecule in esterification also known as?

A

Condensation reaction

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46
Q

Why is the hydrolysis of esters very slow?

A

Water is a poor nucleophile

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47
Q

What types of hydrolysis are there?

A
  • acid-catalysed hydrolysis

* base-catalysed hydrolysis

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48
Q

What is acid-catalysed hydrolysis?

A

When an ester is hydrolysed by refluxing with acid

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49
Q

What acid is usually used in acid-catalysed hydrolysis?

A

Concentrated H2SO4 (or HCl)

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50
Q

What is the organic product of acid-catalysed hydrolysis of an ester?

A

The carboxylic acid

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51
Q

What is the general equation for acid-catalysed hydrolysis of esters?

A

R₁-COOR₂ + H₂O ⇋ R₁-COOH + R₂OH

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52
Q

What does base-catalysed hydrolysis of esters produce?

A

The salt of the carboxylic acid

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53
Q

What are the differences between acid and base catalysed hydrolysis of esters?

A
  • acid - reflux with acid, produces carboxylic acid

* base - boil ester with aqueous NaOH, produces salt of the carboxylic acid

54
Q

How are esters hydrolysed when catalysed with bases?

A

Ester is boiled with aqueous sodium hydroxide

55
Q

What is the general equation for base-catalysed hydrolysis of esters?

A

R₁-COOR₂ + NaOH ⇋ R₁-COO-Na⁺ + R₂OH

56
Q

After base-catalysed hydrolysis, how can the carboxylic acid be produced?

A

By displacement with a strong acid (of the carboxylic acid salt)

57
Q

In base-catalysed hydrolysis of esters, is NaOH a catalyst?

A

No, it is a reactant

58
Q

How can a better yield in base-catalysed hydrolysis be achieved?

A

Equilibrium can be moved further right by having NaOH in excess so more product formed

59
Q

What is saponification?

A

The alkaline hydrolysis of the esters that are animal fats and vegetable oils in soap production

60
Q

When natural fat or oil is used in saponification what is formed?

A

Glycerol and the sodium salt of the long chain fatty acid are formed

61
Q

What are the uses of esters?

A
  • artificial flavourings and perfumes
  • plasticisers
  • solvents
  • biodiesel
62
Q

What is biodiesel a mixture of?

A

Methyl esters of long-chain carboxylic acids

63
Q

How is biodiesel produced?

A

By reacting vegetable oils with methanol in the presence of a catalyst

64
Q

What do plasticisers do? How do they do this?

A

They make polymers less rigid by weakening IMFs between the polymer chains

65
Q

Why are short-chain esters used as solvents?

A

They are volatile, so the ester evaporates easily, leaving the solute behind

66
Q

What are vegetable oils and animal fats esters of?

A

Propane-1,2,3-triol

67
Q

Conditions for acid and alkaline hydrolysis of esters?

A

Heat under reflux

68
Q

What does the functional group for an acyl halide look like?

A

R group attached to C=O bonded to a halide

69
Q

What does the functional group for an acyl anhydride with the same R group look like?

A

R group bonded to C=O, which is bonded to O, bonded to another C=O with the R group on the other side

70
Q

What does the functional group for an acyl anhydride with different R groups look like?

A

R₁ group bonded to C=O, which is bonded to O, bonded to another C=O with the R₂ group on the other side

71
Q

What does the functional group for primary amides look like?

A

R attached to C=O which is bonded to NH₂

72
Q

What does the functional group for secondary amides look like?

A

R₁ attached to C=O which is bonded to N which is bonded to a H and R₂

73
Q

What are secondary amides also known as?

A

N-substituted amides

74
Q

What are tertiary amides also known as?

A

N,N-substituted amides

75
Q

What does the functional group for tertiary amides look like?

A

R₁ attached to C=O which is bonded to N which is bonded to R₂ and R₃

76
Q

Suffix/prefix for acyl halides?

A

-oyl halide

77
Q

Suffix/prefix for acid anhydrides (same R group)?

A

suffix: anhydride

78
Q

Suffix/prefix for acid anhydrides (different R groups)?

A

suffix: R₁-oic R₂-oic anhydride

79
Q

Suffix/prefix for 1° amides?

A

suffix: amide

80
Q

Suffix/prefix for 2° amides?

A

suffix: amide, prefix: N-R₁

81
Q

Suffix/prefix for 3° amides?

A

suffix: amide, prefix: N,N-R₁

82
Q

What are acyl chlorides?

A

Carboxylic acids where the hydroxyl group has been replaced with a Cl atom

83
Q

Are acyl chlorides reactive?

A

Yes, they are highly reactive so make good synthetic intermediates

84
Q

What are acyl chlorides named after?

A

The corresponding carboxylic acid, using the suffix -oyl followed by chloride

85
Q

What are acid anhydrides?

A

Carboxylic acids where the hydroxyl group has been replaced with an alkanoate

86
Q

Are acid anhydrides useful intermediates?

87
Q

What are acid anhydrides named after?

A

Normally after the corresponding acid following by anhydride

If two R groups are not the same, they are still named according to the acid and put in alphabetical order

88
Q

What groups do amides contain?

A

A carbonyl group (C=O) and an amine group (N-H)

89
Q

Where are amides formed?

A

When a H in ammonia or an amine is replaced by a carboxylate group

90
Q

Why are acyl chlorides highly susceptible to nucleophilic attack?

A

They have an extremely electron deficient carbonyl carbon

91
Q

Why do acyl chlorides have an extremely electron deficient carbonyl carbon?

A

Due to the electron withdrawing effect of the highly electronegative chlorine atom

92
Q

How susceptible are acyl chlorides to a nucleophilic attack?

93
Q

What are the steps of the addition-elimination of an acyl chloride?

A
  1. Attraction
  2. Addition
  3. Elimination
  4. Deprotonation
94
Q

Describe each step of the addition-elimination of acyl chlorides

A
  • attraction - carbonyl carbon attracts the lone pair of electrons of the nucleophile
  • addition - nucleophilic addition occurs and carbonyl double bond is broken
  • elimination - addition product eliminates the chlorine as an ion and the carbonyl double bond is reformed
  • deprotonation - the new compound is formed by the removal of a proton
95
Q

What do acyl chlorides react with water to form?

A

The corresponding carboxylic acid

96
Q

What is formed when acyl chlorides are hydrolysed (water) in alkaline solution?

A

The carboxylate ion of the corresponding carboxylic acid instead of the acid

97
Q

What is produced when acyl chlorides react with alcohol?

98
Q

What is an effective way of producing esters?

A

Reacting acyl chlorides with alcohol in an addition-elimination reaction

99
Q

What is usually added in the addition-elimination of acyl chlorides with alcohols?

100
Q

What is the general equation for the reaction of acyl chlorides with alcohols?

A

R₁COCl + R₂OH → R₁COOR₂ + HCl

101
Q

Why is a base added in the reaction of acyl chlorides and alcohols?

A

To neutralise the liberated HCl

102
Q

What does adding a base in the reaction of acyl chlorides and alcohols avoid?

A

The equilibrium problem associated with acid catalysed esterfication

103
Q

Difference between amines and amides?

A

Amides functional group contains the C=O

104
Q

Are amines nucleophiles?

105
Q

Why are amines nucleophiles?

A

They have a lone pair of electrons on the nitrogen atom

106
Q

What does the reaction of acyl chlorides with primary amines produce?

A

An N-substituted amide

107
Q

What is the general equation for the reaction of acyl chlorides with primary amines?

A

R₁COCl + R₂NH₃ → R₁CONHR₂ + HCl

108
Q

Why is ammonia a nucleophile?

A

It has a lone pair of electrons on the nitrogen atom

109
Q

What is formed when acyl chlorides react with ammonia?

110
Q

What is the general equation for the reaction of acyl chlorides with ammonia?

A

RCOCl + 2NH₃ → RCONH₂ + NH₄Cl

111
Q

Why is an excess of ammonia used in the reaction with acyl chlorides?

A

To remove (neutralise) the hydrogen chloride eliminated at the end of the reaction

112
Q

What do acid anhydrides react with water to produce?

A

Two carboxylic acids

113
Q

What are the conditions when acid anhydrides and water react?

A

The reaction is slow, and the mixture is warmed

114
Q

What do acid anhydrides react with alcohol to produce?

A

An ester and a carboxylic acid

115
Q

What are the conditions when acid anhydrides and alcohol react?

A

Gentle heating

116
Q

What do acid anhydrides react with primary amines to produce?

A

An N-substituted amide and a carboxylic acid

117
Q

What are the conditions when acid anhydrides and primary amines react?

A

Gentle heating

118
Q

What do acid anhydrides react with ammonia to produce?

A

An amide and a carboxylic acid

119
Q

What are the conditions when acid anhydrides and ammonia react?

A

Reacts slowly when mixture is warmed

120
Q

What reaction produces aspirin?

A

The acylation of 2-hydroxybenzene carboxylic acid (salicylic acid) with ethanoic anhydride

121
Q

What are the industrial advantages of ethanoic anhydride over ethanoyl chloride in the manufacture of aspirin?

A
  • cheaper
  • less corrosive
  • doesn’t react with water as readily
  • safer as the by product of its reaction is ethanoic acid rather than HCl which is a strong acid
122
Q

What are the conditions for acylation using acyl chlorides?

A

Room temperature for all

123
Q

What mechanism is involved in the acylation of acyl chlorides?

A

Nucleophilic addition-elimation

124
Q

What are the observations in the acylation of acyl chlorides?

A

White misty fumes in all cases

125
Q

What are the conditions for acylation using acid anhydrides?

A

Room temperature for all

126
Q

What are the observations in the acylation of acid anhydrides?

A

White misty fumes in all cases

127
Q

Do you need to know the mechanism for acylation using acid anhydrides?

128
Q

What is the general equation for the reaction of acid anhydrides with water?

A

R₁-COOCO-R₂ + H₂O → R₁-COOH + R₂COOH

129
Q

What is the general equation for the reaction of acid anhydrides with alcohols?

A

R₁-COOCO-R₂ + R₃-OH → R₁-COO-R₃ + R₂COOH

130
Q

What is the general equation for the reaction of acid anhydrides with primary amines?

A

R₁-COOCO-R₂ + 2R₃NH₂ → R₁-CONH-R₃ + R₂COO⁻ R₃NH₃⁺

131
Q

What is the general equation for the reaction of acid anhydrides with ammonia?

A

R₁-COOCO-R₂ + 2NH₃ → R₁-CONH₂ + R₂COO⁻NH₄⁺

AQA A Level Organic Chemistry (16 decks)

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