9. Carboxylic Acids and Derivatives Flashcards
(131 cards)
1
Q
What is the functional group of carboxylic acids?
A
R - COOH
2
Q
Are carboxylic acids weak or strong acids?
A
Weak
3
Q
Why do carboxylic acids not fully dissociate in water?
A
As they are weak acids
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⁺
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
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
7
Q
What are carboxylic acids produced by?
A
The oxidation of primary alcohols or aldehydes
8
Q
What happens when ethanol is exposed to air?
A
It oxidises to ethanoic acid
9
Q
Why can wine taste vinegary if left open?
A
The ethanol oxidises to ethanoic acid
10
Q
Where is methanoic acid found naturally?
A
In an ant bite; it can cause irritation
11
Q
Where is ethanedioic acid found naturally?
A
As a metal salt in rhubarb and gives it a sour taste
12
Q
What is ethanedioic acid?
A
A poisonous white crystalline solid
13
Q
Where is benzene carboxylic acid (benzoic acid) found?
A
Raspberries and some tree barks
14
Q
How is benzoic acid used?
A
As a preservative and an antioxidant in numerous foods
15
Q
How are carboxylic acids named?
A
Using the suffix -oic acid
16
Q
What do carboxylic acids react with alkalis to form?
A
Water and carboxylate salts
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
18
Q
Equation for ethanoic acid with sodium hydroxide?
A
CH3COOH + NaOH → CH3COONa + H2O
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
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
21
Q
What do carboxylic acids react with carbonates and hydrogen carbonates to form?
A
Salt, water and carbon dioxide
22
Q
Are carbonates and hydrogen carbonates weak or strong bases?
A
Weak
23
Q
What is a general equation for the reaction of carboxylic acids with sodium carbonates?
A
R-COOH + Na2CO3 → RCOO⁻⁻Na⁺ + CO2 + H2O
24
Q
What is a general equation for the reaction of carboxylic acids with sodium hydrogencarbonates?
A
R-COOH + NaHCO3 → RCOO⁻⁻Na⁺ + CO2 + H2O
25
How does carboxylic acids being weak acids affect the rate of reaction with carbonates/hydrogen carbonates?
The reaction rate is slower than strong acids (e.g. HCl, H2SO4) - however still sufficient to produce CO2
26
In the reaction of carboxylic acids and carbonates/hydrogen carbonates, how can it be confirmed that the reactant is a carboxylic acid?
Presence of CO2 can be confirmed by passing gas through limewater
27
Describe the equipment used to test for carboxylic acids
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
28
What do carboxylic acids react with alcohols to form?
An ester and water
29
What must be present for carboxylic acids to react with alcohols?
Concentrated sulphuric acid
30
What is esterification?
When carboxylic acids react with alcohols in the presence of concentrated sulphuric acid
31
What do methanol and ethanoic acid react to form?
Methyl ethanoate
32
What does the H2SO4 act as in esterification?
A catalyst
33
What conditions is esterification carried out under?
Under reflux
34
When are esters produced?
In the reaction between carboxylic acids and alcohols
35
What is the functional group for esters?
R1 - COO - R2
36
What are the names of esters based on?
The carboxylic acid and alcohol from which they are produced
37
What is the first component of the ester name derived from?
The number of carbons in the alcohol (ending with -yl)
38
What is the second component of the ester name derived from?
The number of carbons in the carboxylic acid (ending with -oate)
39
What reactants make methyl propanoate?
Methanol and propanoic acid
40
What is the reverse of esterification?
Hydrolysis of esters
41
What is the hydrolysis of esters?
The reverse of esterfication
42
What is produced in the hydrolysis of esters?
An acid and an alcohol
43
Why is hydrolysis of esters possible?
The carbonyl C is susceptible to nucleophilic attack
44
What does hydrolysis of esters involve, considering that esterification involves the removal of a water molecule?
The addition of a water molecule
45
What is the removal of a water molecule in esterification also known as?
Condensation reaction
46
Why is the hydrolysis of esters very slow?
Water is a poor nucleophile
47
What types of hydrolysis are there?
* acid-catalysed hydrolysis
| * base-catalysed hydrolysis
48
What is acid-catalysed hydrolysis?
When an ester is hydrolysed by refluxing with acid
49
What acid is usually used in acid-catalysed hydrolysis?
Concentrated H2SO4 (or HCl)
50
What is the organic product of acid-catalysed hydrolysis of an ester?
The carboxylic acid
51
What is the general equation for acid-catalysed hydrolysis of esters?
R₁-COOR₂ + H₂O ⇋ R₁-COOH + R₂OH
52
What does base-catalysed hydrolysis of esters produce?
The salt of the carboxylic acid
53
What are the differences between acid and base catalysed hydrolysis of esters?
* acid - reflux with acid, produces carboxylic acid
| * base - boil ester with aqueous NaOH, produces salt of the carboxylic acid
54
How are esters hydrolysed when catalysed with bases?
Ester is boiled with aqueous sodium hydroxide
55
What is the general equation for base-catalysed hydrolysis of esters?
R₁-COOR₂ + NaOH ⇋ R₁-COO-Na⁺ + R₂OH
56
After base-catalysed hydrolysis, how can the carboxylic acid be produced?
By displacement with a strong acid (of the carboxylic acid salt)
57
In base-catalysed hydrolysis of esters, is NaOH a catalyst?
No, it is a reactant
58
How can a better yield in base-catalysed hydrolysis be achieved?
Equilibrium can be moved further right by having NaOH in excess so more product formed
59
What is saponification?
The alkaline hydrolysis of the esters that are animal fats and vegetable oils in soap production
60
When natural fat or oil is used in saponification what is formed?
Glycerol and the sodium salt of the long chain fatty acid are formed
61
What are the uses of esters?
* artificial flavourings and perfumes
* plasticisers
* solvents
* biodiesel
62
What is biodiesel a mixture of?
Methyl esters of long-chain carboxylic acids
63
How is biodiesel produced?
By reacting vegetable oils with methanol in the presence of a catalyst
64
What do plasticisers do? How do they do this?
They make polymers less rigid by weakening IMFs between the polymer chains
65
Why are short-chain esters used as solvents?
They are volatile, so the ester evaporates easily, leaving the solute behind
66
What are vegetable oils and animal fats esters of?
Propane-1,2,3-triol
67
Conditions for acid and alkaline hydrolysis of esters?
Heat under reflux
68
What does the functional group for an acyl halide look like?
R group attached to C=O bonded to a halide
69
What does the functional group for an acyl anhydride with the same R group look like?
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
What does the functional group for an acyl anhydride with different R groups look like?
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
What does the functional group for primary amides look like?
R attached to C=O which is bonded to NH₂
72
What does the functional group for secondary amides look like?
R₁ attached to C=O which is bonded to N which is bonded to a H and R₂
73
What are secondary amides also known as?
N-substituted amides
74
What are tertiary amides also known as?
N,N-substituted amides
75
What does the functional group for tertiary amides look like?
R₁ attached to C=O which is bonded to N which is bonded to R₂ and R₃
76
Suffix/prefix for acyl halides?
-oyl halide
77
Suffix/prefix for acid anhydrides (same R group)?
suffix: anhydride
78
Suffix/prefix for acid anhydrides (different R groups)?
suffix: R₁-oic R₂-oic anhydride
79
Suffix/prefix for 1° amides?
suffix: amide
80
Suffix/prefix for 2° amides?
suffix: amide, prefix: N-R₁
81
Suffix/prefix for 3° amides?
suffix: amide, prefix: N,N-R₁
82
What are acyl chlorides?
Carboxylic acids where the hydroxyl group has been replaced with a Cl atom
83
Are acyl chlorides reactive?
Yes, they are highly reactive so make good synthetic intermediates
84
What are acyl chlorides named after?
The corresponding carboxylic acid, using the suffix -oyl followed by chloride
85
What are acid anhydrides?
Carboxylic acids where the hydroxyl group has been replaced with an alkanoate
86
Are acid anhydrides useful intermediates?
Yes
87
What are acid anhydrides named after?
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
What groups do amides contain?
A carbonyl group (C=O) and an amine group (N-H)
89
Where are amides formed?
When a H in ammonia or an amine is replaced by a carboxylate group
90
Why are acyl chlorides highly susceptible to nucleophilic attack?
They have an extremely electron deficient carbonyl carbon
91
Why do acyl chlorides have an extremely electron deficient carbonyl carbon?
Due to the electron withdrawing effect of the highly electronegative chlorine atom
92
How susceptible are acyl chlorides to a nucleophilic attack?
Highly
93
What are the steps of the addition-elimination of an acyl chloride?
1. Attraction
2. Addition
3. Elimination
4. Deprotonation
94
Describe each step of the addition-elimination of acyl chlorides
* 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
What do acyl chlorides react with water to form?
The corresponding carboxylic acid
96
What is formed when acyl chlorides are hydrolysed (water) in alkaline solution?
The carboxylate ion of the corresponding carboxylic acid instead of the acid
97
What is produced when acyl chlorides react with alcohol?
Ester
98
What is an effective way of producing esters?
Reacting acyl chlorides with alcohol in an addition-elimination reaction
99
What is usually added in the addition-elimination of acyl chlorides with alcohols?
A base
100
What is the general equation for the reaction of acyl chlorides with alcohols?
R₁COCl + R₂OH → R₁COOR₂ + HCl
101
Why is a base added in the reaction of acyl chlorides and alcohols?
To neutralise the liberated HCl
102
What does adding a base in the reaction of acyl chlorides and alcohols avoid?
The equilibrium problem associated with acid catalysed esterfication
103
Difference between amines and amides?
Amides functional group contains the C=O
104
Are amines nucleophiles?
Yes
105
Why are amines nucleophiles?
They have a lone pair of electrons on the nitrogen atom
106
What does the reaction of acyl chlorides with primary amines produce?
An N-substituted amide
107
What is the general equation for the reaction of acyl chlorides with primary amines?
R₁COCl + R₂NH₃ → R₁CONHR₂ + HCl
108
Why is ammonia a nucleophile?
It has a lone pair of electrons on the nitrogen atom
109
What is formed when acyl chlorides react with ammonia?
An amide
110
What is the general equation for the reaction of acyl chlorides with ammonia?
RCOCl + 2NH₃ → RCONH₂ + NH₄Cl
111
Why is an excess of ammonia used in the reaction with acyl chlorides?
To remove (neutralise) the hydrogen chloride eliminated at the end of the reaction
112
What do acid anhydrides react with water to produce?
Two carboxylic acids
113
What are the conditions when acid anhydrides and water react?
The reaction is slow, and the mixture is warmed
114
What do acid anhydrides react with alcohol to produce?
An ester and a carboxylic acid
115
What are the conditions when acid anhydrides and alcohol react?
Gentle heating
116
What do acid anhydrides react with primary amines to produce?
An N-substituted amide and a carboxylic acid
117
What are the conditions when acid anhydrides and primary amines react?
Gentle heating
118
What do acid anhydrides react with ammonia to produce?
An amide and a carboxylic acid
119
What are the conditions when acid anhydrides and ammonia react?
Reacts slowly when mixture is warmed
120
What reaction produces aspirin?
The acylation of 2-hydroxybenzene carboxylic acid (salicylic acid) with ethanoic anhydride
121
What are the industrial advantages of ethanoic anhydride over ethanoyl chloride in the manufacture of aspirin?
* 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
What are the conditions for acylation using acyl chlorides?
Room temperature for all
123
What mechanism is involved in the acylation of acyl chlorides?
Nucleophilic addition-elimation
124
What are the observations in the acylation of acyl chlorides?
White misty fumes in all cases
125
What are the conditions for acylation using acid anhydrides?
Room temperature for all
126
What are the observations in the acylation of acid anhydrides?
White misty fumes in all cases
127
Do you need to know the mechanism for acylation using acid anhydrides?
No
128
What is the general equation for the reaction of acid anhydrides with water?
R₁-COOCO-R₂ + H₂O → R₁-COOH + R₂COOH
129
What is the general equation for the reaction of acid anhydrides with alcohols?
R₁-COOCO-R₂ + R₃-OH → R₁-COO-R₃ + R₂COOH
130
What is the general equation for the reaction of acid anhydrides with primary amines?
R₁-COOCO-R₂ + 2R₃NH₂ → R₁-CONH-R₃ + R₂COO⁻ R₃NH₃⁺
131
What is the general equation for the reaction of acid anhydrides with ammonia?
R₁-COOCO-R₂ + 2NH₃ → R₁-CONH₂ + R₂COO⁻NH₄⁺
