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AQA A Level Chemistry > Carboxylic Acids and its Derivatives > Flashcards

Carboxylic Acids and its Derivatives Flashcards

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1
Q

Functional group of carboxylic acids

A

RCOOH.
C=O and C-OH

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2
Q

Why are the intermolecular forces between carboxylic acid molecules relatively strong

A

Due to the presence of two polar groups, C=O and C-OH

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3
Q

Why do carboxylic acids have a higher boiling point than alcohols

A

Each carboxylic acid molecule can form 2 hydrogen bonds but each alcohol molecule can only form one. More energy is needed to break the hydrogen bonds between carboxylic acid molecules.

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4
Q

Why are some carboxylic acid molecules soluble in water

A

They can form hydrogen bonds with water molecules because it has a polar -COOH group. The -COOH group can form hydrogen bonds with water molecules. ONLY CARBOXYLIC ACIDS 1 to 4 are soluble

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5
Q

Why is benzoic acid only slightly soluble in water

A

The -COOH group can form hydrogen bonds with water molecules. However, it is only slightly soluble because the benzene ring is non-polar

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6
Q

Describe the reaction, conditions and reagents needed to go from a nitrile to a carboxylic acid

A

Reaction : Acid hydrolysis
Reagent : Dilute HCl
Conditions : Heat under reflux

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7
Q

nitrile + water + hydrochloric acid =

A

Carboxylic acid + ammonium chloride

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8
Q

Are carboxylic acids strong or weak acids

A

Weak. They only partially dissociate in solution

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9
Q

How are carboxylate salts produced

A

Acid-base reactions

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10
Q

ethanoic acid + NaOH ——–>

A

CH3-COO-Na+ + H2O

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11
Q

What are the reagents and conditions for acid-base reactions in the production of carboxylate salts

A

Reagent : AQEUOUS sodium carbonate/hydroxide
Conditions : Room temperature

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12
Q

propanoic acid + sodium carbonate =

A

sodium propanoate + water + carbon dioxide

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13
Q

What is the test for the -COOH group

A

Add aqueous sodium carbonate to the compound. Bubble the gas produced into limewater. Fizzing/effervescence is observed. The colourless gas (CO2) turns limewater cloudy

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14
Q

Describe esterification

A

When a carboxylic acid is heater under reflux with an alcohol in the presence of an acid catalyst such as conc sulfuric acid, an ester is formed

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15
Q

What do carboxylic acids do to carbonates even though they are weak acids

A

They liberate the CO2 from carbonates.

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16
Q

What type of reaction is it when esters are formed from the reaction between carboxylic acids and alcohols

A

Reversible reaction

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17
Q

Why is the yield of esters low when produced from reacting carboxylic acids and alcohols

A

It is a reversible reaction and results in an equilibrium therefore low yield

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18
Q

Reagents and conditions for esterification

A

Reagents: Alcohol and concentrated sulfuric acid
Conditions : Heat under reflux

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19
Q

How to draw esters

A

Break the -OH off the carboxylic acid
Break the H off the -OH on the alcohol
Connect the O of the alcohol to the main C of the carboxylic acid.

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20
Q

How to name esters

A

The alcohol part first and then the carboxylic acid part.
e,g, propyl ethanoate

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21
Q

Functions of concentrated sulphuric acid in esterification

A

Acts as the catalyst for the reaction
Absorbs the water formed, driving the equilibrium to the right and increasing the yield of the ester

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22
Q

Functional group for esters

A

-COOR
There is a C=O and and -OR attached to the same carbon

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23
Q

Common uses of esters

A

In solvents
Plasticisers
Perfumes
Food flavourings

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24
Q

Main use of polyesters

A

Clothing

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25
How can esters be produced by acyl chlorides
When acyl chloride reacts with an alcohol at room temperature an ester and HCl is formed. This reaction is called Nucleophilic addition-elimination
26
What is the advantage of making esters by reacting an acyl chloride with alcohol
The reaction goes to completion giving a higher yield of the ester
27
What is produced in the acid hydrolysis of esters
A carboxylic acid and an alcohol
28
Conditions and reagents for acid hydrolysis of esters
Conditions : Heat under reflux Reagent: dilute HCl/H2SO4 - acts as catalyst
29
ester + water ----------> <----------
Carboxylic acid + alcohol
30
Describe what happens in acid hydrolysis of esters
Ester is heated with dilute HCl C-O bond in ester is broken using water Carboxylic acid and alcohol produced
31
Describe what happens in alkaline hydrolysis of water
Ester is heated with aqueous NaOH/KOH A carboxylate salt and an alcohol are formed
32
Advantages of alkaline hydrolysis of esters
Reaction goes to completion giving a higher yield Products are easier to separate. Alcohol formed can be distilled off.
33
ester + NaOH/base ------->
carboxylate salt + alcohol
34
How are soaps made
By the alkaline hydrolysis of fats and oils. Saponification The sodium salts of the carboxylic acid and the alcohol, glycerol, are formed
35
Trigylceride + NaOH =
Soap + glycerol
36
What is the chemical name for glycerol
propane-1,2,3-triol
37
What are the esters of glycerol / propane-1,2,3-triol
Vegetable oils and animal fats
38
How do vegetable oils and animals fats produce soaps and glycerol
Through alkaline hydrolysis
39
What is biodiesal
A mixture of methyl esters of long-chain carboxylic acids
40
How is biodiesel produced
By reaction vegetable oils with methanol in the presence of a catalyst. This forms propan-1,2,3-triol and biodiesal
41
Describe esterification of acid anhydrides with alcohols
The bottom part of the acid anhydride which looks like a carboxylic acid (RCOO) breaks off. The H of the alcohol also breaks off. This forms an ester and carboxylic acid
42
What is formed when a carboxylic acid is heated under reflux with an alcohol in the presence of an acid catalyst
An ester
43
How can we tell if an ester is formed
A fruity smell
44
How would you convert ethanoic acid into propyl ethanoate
Heat under reflux ethanoic acid with propan-1-ol and concentrated sulfuric acid as the catalyst
45
Do esters have hydrogen bonding
Not between esters but can form hydrogen bonds with water
46
Explain why the ester methyl methanoate has a much lower boiling point than its isomer ethanoic acid and why ethanoic acid has a lower boiling point than propanoic acid.
There are hydrogen bonds between molecules of ethanoic acid because it has a polar -COOH group. The ester cannot form hydrogen bonds and has weaker permanent dipole-dipole interactions and Van der Waals forces between its molecules. Less energy is needed to break the weaker intermolecular forces in the ester. Ethanoic acid has fewer electrosn than propanoic acid, so the Van der Waals forces between molecules of ethanoic acid are weaker. Less energy is needed to break the weaker intermolecular forces in ethanoic acid.
47
What are esters isomeric with
Carboxylic acids
48
Suggest 3 hazards that could occur when using propanoyl chloride to make the ester and describe how you would minimise this risk
Propanoyl chloride is toxic, use a fume cupboard Hydrogen chloride is formed which is toxic, use a fume cupboard Propanoyl chloride is corrosive, wear gloves when handling
49
What happens in the hydrolysis of esters
The C-O bond in ester is broken using water
50
Typical acid hydrolysis of esters reaction
Ester + water ⇌ Carboxylic acid + alcohol Heated with dilute HCL/ dilute H2SO4
51
Condition for acid hydrolysis of esters
Heat under reflux
52
Typical alkaline hydrolysis of esters reaction
Ester + NaOH/KOH -------> Carboxylate salt + alcohol
53
Advantages of alkaline hydrolysis of esters
Reaction goes to completion giving a higher yield The products are easier to separate. The alcohol can be distilled off
54
What happens in trans-esterification
A trigylceride/ tri-ester reacts with an alcohol to form ester + glycerol The ester is then used as biodiesal
55
Triglyceride + NaOH -------->
soap + glycerol
56
Triglyceride + alcohol (methanol)
biodiesal + glycerol
57
Functional group of acyl chlorides
COCl. The C=O bond is a double bond
58
How to name acyl chlorides
-oyl chloride
59
Name CH3COCl
Ethanoyl chloride
60
Why do acyl chlorides get attacked by nucleophiles
The carbonyl carbon in an acyl chloride is very delta positive because the chlorine atom and oxygen is highly electronegative.
61
What are typical reaction of acyl chlorides called
Nucleophilic addition-elimination reactions
62
Hazards when using acyl chlorides and how to minimise
They are toxic so use a fume cupboard They are corrosive so wear gloves when handling
63
Acyl chloride + water =
Carboxylic acid + HCl white fumes of hydrogen chloride gas seen
64
Acyl chloride + alcohol/phenols =
Ester + HCl
65
Acyl chloride + concentrated ammonia
amide + NH4Cl
66
Acyl chloride + primary amines =
N-substituted amide + HCl
67
Conditions for all acyl chloride reactions
Room temperature
68
How do acid anhydrides react
In the same way as acyl chlorides but not as vigorously
69
Conditions for acid anhydrides reactions
Heat under reflux
70
What do acid anhydrides look like
CH3C(O)OCH3C(O) 2 C=O bonds like a reflection about the central oxygen atom
71
Acid anhydride + water =
Carboxylic acid
72
Acid anhydride + alcohol =
Ester + carboxylic acid
73
Acid anhydride + ammonia =
Primary amide + ammonium carboxylate
74
Acid anhydride + primary amines =
N-substituted primary amine + ion mix
75
What are the industrial advantages of ethanoic anhydride over ethanoyl chloride in the manufacture of the drug aspirin
It is cheaper Less corrosive Less vulnerable to hydrolysis Less dangerous to use
76
Suggest why chloroethanoic acid is a stronger acid than ethanoic acid.
Cl is an electron withdrawing group or negative inductive effect Stabilises/reduces charge on COO- Weakens the O-H bond / increase polarity of O-H bond

AQA A Level Chemistry (36 decks)

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