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

Carboxylic Acids and its Derivatives Flashcards

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
Q

How can esters be produced by acyl chlorides

A

When acyl chloride reacts with an alcohol at room temperature an ester and HCl is formed.
This reaction is called Nucleophilic addition-elimination

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26
Q

What is the advantage of making esters by reacting an acyl chloride with alcohol

A

The reaction goes to completion giving a higher yield of the ester

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27
Q

What is produced in the acid hydrolysis of esters

A

A carboxylic acid and an alcohol

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28
Q

Conditions and reagents for acid hydrolysis of esters

A

Conditions : Heat under reflux
Reagent: dilute HCl/H2SO4 - acts as catalyst

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29
Q

ester + water ———->
<———-

A

Carboxylic acid + alcohol

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30
Q

Describe what happens in acid hydrolysis of esters

A

Ester is heated with dilute HCl
C-O bond in ester is broken using water
Carboxylic acid and alcohol produced

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31
Q

Describe what happens in alkaline hydrolysis of water

A

Ester is heated with aqueous NaOH/KOH
A carboxylate salt and an alcohol are formed

32
Q

Advantages of alkaline hydrolysis of esters

A

Reaction goes to completion giving a higher yield
Products are easier to separate. Alcohol formed can be distilled off.

33
Q

ester + NaOH/base ——->

A

carboxylate salt + alcohol

34
Q

How are soaps made

A

By the alkaline hydrolysis of fats and oils. Saponification
The sodium salts of the carboxylic acid and the alcohol, glycerol, are formed

35
Q

Trigylceride + NaOH =

A

Soap + glycerol

36
Q

What is the chemical name for glycerol

A

propane-1,2,3-triol

37
Q

What are the esters of glycerol / propane-1,2,3-triol

A

Vegetable oils and animal fats

38
Q

How do vegetable oils and animals fats produce soaps and glycerol

A

Through alkaline hydrolysis

39
Q

What is biodiesal

A

A mixture of methyl esters of long-chain carboxylic acids

40
Q

How is biodiesel produced

A

By reaction vegetable oils with methanol in the presence of a catalyst. This forms propan-1,2,3-triol and biodiesal

41
Q

Describe esterification of acid anhydrides with alcohols

A

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
Q

What is formed when a carboxylic acid is heated under reflux with an alcohol in the presence of an acid catalyst

43
Q

How can we tell if an ester is formed

A

A fruity smell

44
Q

How would you convert ethanoic acid into propyl ethanoate

A

Heat under reflux ethanoic acid with propan-1-ol and concentrated sulfuric acid as the catalyst

45
Q

Do esters have hydrogen bonding

A

Not between esters but can form hydrogen bonds with water

46
Q

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.

A

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
Q

What are esters isomeric with

A

Carboxylic acids

48
Q

Suggest 3 hazards that could occur when using propanoyl chloride to make the ester and describe how you would minimise this risk

A

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
Q

What happens in the hydrolysis of esters

A

The C-O bond in ester is broken using water

50
Q

Typical acid hydrolysis of esters reaction

A

Ester + water ⇌ Carboxylic acid + alcohol
Heated with dilute HCL/ dilute H2SO4

51
Q

Condition for acid hydrolysis of esters

A

Heat under reflux

52
Q

Typical alkaline hydrolysis of esters reaction

A

Ester + NaOH/KOH ——-> Carboxylate salt + alcohol

53
Q

Advantages of alkaline hydrolysis of esters

A

Reaction goes to completion giving a higher yield
The products are easier to separate. The alcohol can be distilled off

54
Q

What happens in trans-esterification

A

A trigylceride/ tri-ester reacts with an alcohol to form ester + glycerol
The ester is then used as biodiesal

55
Q

Triglyceride + NaOH ——–>

A

soap + glycerol

56
Q

Triglyceride + alcohol (methanol)

A

biodiesal + glycerol

57
Q

Functional group of acyl chlorides

A

COCl.
The C=O bond is a double bond

58
Q

How to name acyl chlorides

A

-oyl chloride

59
Q

Name CH3COCl

A

Ethanoyl chloride

60
Q

Why do acyl chlorides get attacked by nucleophiles

A

The carbonyl carbon in an acyl chloride is very delta positive because the chlorine atom and oxygen is highly electronegative.

61
Q

What are typical reaction of acyl chlorides called

A

Nucleophilic addition-elimination reactions

62
Q

Hazards when using acyl chlorides and how to minimise

A

They are toxic so use a fume cupboard
They are corrosive so wear gloves when handling

63
Q

Acyl chloride + water =

A

Carboxylic acid + HCl
white fumes of hydrogen chloride gas seen

64
Q

Acyl chloride + alcohol/phenols =

A

Ester + HCl

65
Q

Acyl chloride + concentrated ammonia

A

amide + NH4Cl

66
Q

Acyl chloride + primary amines =

A

N-substituted amide + HCl

67
Q

Conditions for all acyl chloride reactions

A

Room temperature

68
Q

How do acid anhydrides react

A

In the same way as acyl chlorides but not as vigorously

69
Q

Conditions for acid anhydrides reactions

A

Heat under reflux

70
Q

What do acid anhydrides look like

A

CH3C(O)OCH3C(O)
2 C=O bonds

like a reflection about the central oxygen atom

71
Q

Acid anhydride + water =

A

Carboxylic acid

72
Q

Acid anhydride + alcohol =

A

Ester + carboxylic acid

73
Q

Acid anhydride + ammonia =

A

Primary amide + ammonium carboxylate

74
Q

Acid anhydride + primary amines =

A

N-substituted primary amine + ion mix

75
Q

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

A

It is cheaper
Less corrosive
Less vulnerable to hydrolysis
Less dangerous to use

76
Q

Suggest why chloroethanoic acid is a stronger acid than ethanoic acid.

A

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 (31 decks)

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