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Chemistry Year 13 > Carboxylic acids and derivatives 3.3.9 > Flashcards

Carboxylic acids and derivatives 3.3.9 Flashcards

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1
Q

What type of acids are carboxylic acids and what does this mean

A

Weak acids - dissociate partially to form a H+ ion and a carboxylate ion

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2
Q

what functional group does a carboxylic acid have

A
  • COOH
    ( carbonyl group C=O)
    ( Hydroxyl group O-H)
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3
Q

What products does a carboxylic acid and a carbonate produce

A

a salt , carbon dioxide gas and water

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4
Q

What is the chemical test for a carboxylic acid

A

Add sodium carbonate
result : gentle fizzing / effervescence

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5
Q

What functional group does an ester have

A
  • COO -
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6
Q

How can an ester be produced from carboxylic acids

A

React carboxylic acids with an alcohol and a sulfuric acid catalyst

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7
Q

What kind of catalyst is sulfuric acid

A

homogenous catalyst

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8
Q

How is an ester produced when reacting with an acid anhydride

A

React acid anhydride with an alcohol

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9
Q

How do we name esters when formed from a carboxylic acid

A

The alkyl group is formed from the alcohol and is named first . e.g. ethyl , methyl etc
The rest of the molecule is former from the carboxylic acid
Remove “-oic acid” and replace it with “-oate”
Named second when naming an ester
When we name esters with alkyl branches e.g. ch3 , we number from the carbons in the C-O-C part

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10
Q

What type of things are esters used in , in the commercially and industrial processes

A
  • Perfumes and food savouring
  • Solvents
  • Plasticisers
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11
Q

How are esters used in perfumes and food savouring

A

Some esters have sweet smells such as pear drops
This makes them ideal in fragrances and food products

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12
Q

How are esters used in solvents

A
  • Esters are polar so other compounds will dissolve in esters.
  • Rhey also have low boiling points and evaporate easily .
    This makes them valuable in making glues
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13
Q

How are esters used in plasticisers

A

Esters are used to make plastics more flexible during the polymerisation process

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14
Q

How do plastics that are made from esters become more brittle

A

The esters can leach out of the plastic over time . This could happen if plastic is left out in the sun for too long ( UV causes plastic to become brittle )

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15
Q

How can ester hydrolysis be sped up

A
  • Using an acid ( acid hydrolysis )
  • Using a base ( base hydrolysis)
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16
Q

What is the process acid hydrolysis

A

Use a dilute acid to split an ester into a carboxylic acid and an alcohol

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17
Q

What condition and reagent is used in acid hydrolysis

A

Sulfuric / hydrochloric acid
Conducted under reflux

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18
Q

What is the reaction for a acid hydrolysis reaction

A

Ester + water => carboxylic acid + alcohol

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19
Q

What’s the process of base hydrolysis

A

Use a dilute base to split an ester into a carboxylate ion and an alcohol

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20
Q

What condition and reagent is base hydrolysis in

A

Reagent : Sodium hydroxide
Condition : distillate , aqueous

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21
Q

What’s the reaction of a base hydrolysis reaction

A

Ester + Hydroxide ( -OH) => carboxylate + alcohol

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22
Q

How do we produce an ester which makes fats and oils

A

React glycerol ( alcohol) and fatty acids ( carboxylic acids)

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23
Q

What is the chemical name for glycerol

A

Propane-1,2,3-triol

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24
Q

What is glycerol reacted with

A

Long chain fatty acids which can be saturated ( no double bonds) or unsaturated (contains at least 1 double bond )

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25
Q

What is a polysaturated fatty acid

A

Contains more than 1 double bond

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26
Q

What is an oil

A

an ester

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27
Q

What are some properties of vegetable oil

A
  • Unsaturated hydrocarbon chains that aren’t straight
  • This means that chains can’t pack closely together
  • This means that they have lower Van der Waals forces
  • Lower melting points and are liquid at room temperature
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28
Q

What are fats?

A

An ester

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29
Q

What are some properties of animal fats ?

A
  • They have saturated hydrocarbon chains that are straight and more uniform than oils
  • This means the chains can pack together closely
  • This means higher Van der Waals forces
  • This means higher melting points
  • Therefore solids at room temperature
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30
Q

How can we make soap

A

Animal fats and vegetable oils can be hydrolysed by heating them with sodium hydroxide

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31
Q

what reaction is used when using animal fat to make a soap

A

animal fat + sodium hydroxide => glycerol + sodium salt (soap)

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32
Q

How can biodiesel be formed

A

Vegetable oils can be converted into biodiesel by reacting oils with methanol and a potassium hydroxide as a catalyst

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33
Q

What is biodiesel

A

A mixture of fatty acids made from methyl esters and can be made from rapeseed oil

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34
Q

What is the reaction to form biodiesel

A

Oil + methanol => ^(KOH as catalyst) Glycerol + methyl ester

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35
Q

What are some physical properties of carboxylic acids

A
  • Can form hydrogen bonds with water molecules
  • This means that carboxylic acids up to , and including , four carbons are completely soluble in water
  • Also forms hydrogen bonds with one another in solid state
  • Therefore have higher melting points than alkanes
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36
Q

what is the equation for a carboxylic acid reacting with a metal

A

Acid + metal (Na) => salt + hydrogen

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37
Q

What is the reaction between carboxylic acid and an alkali

A

Acid + Alkali ( NaOH) => salt + water

38
Q

What is the reaction of a carboxylic acid and a carbonate

A

acid + carbonate (Na2CO3) => salt + water + carbon dioxide

39
Q

what is biodiesel used for

A

Source of fuel for motor vehicles
it’s a renewable fuel

40
Q

What is the acyl chloride functional group

A

-COCl

41
Q

How is an acyl chloride named

A

By finding the longest carbon chain and then adding “-oyl chloride “ on the end

42
Q

What is the reaction of acyl chloride and water

A

Acyl chloride + water -> carboxylic acid + hydrogen chloride gas

43
Q

What are the observations produced and what kind of reactions are with acyl chlorides

A

Vigorous reaction
White misty fumes of hydrogen chloride gas produced
(HCl) gas produced

44
Q

What is the reaction with acyl chloride and ammonia

A

Acyl chloride + ammonia -> amide + hydrogen chloride gas

45
Q

What is the functional group of an amide

A

CONH2

46
Q

What’s the reaction between acyl chloride and an alcohol

A

Acyl chloride + alcohol => ester + hydrogen chloride gas

47
Q

What is the reaction between an acyl chloride and a primary amine

A

Acyl chloride + primary amine => N- substituted amide + hydrogen chloride gas

48
Q

What is an N- substituted amide

A

Usually an amide would contain NH2
But one of the hydrogens is replaced by an alkyl group

49
Q

How would you name an N- substituted amide

A

Put an N - ( alkyl group that replaced the hydrogen ) and then the amide
Example : N- methyl ethanamide

50
Q

In acyl chloride reactions what is cl substituted for

A

Either an oxygen or nitrogen

51
Q

What do acyl chlorides react with

A

Water
Ammonia
Alcohol
Primary amines

52
Q

What is an acid anhydride

A

A molecule made from 2 carboxylic acids that are the same

53
Q

How are acid anhydrides named

A

By naming the known carboxylic acid it’s made from and removing the “-acid” and adding “-anhydride” on the end

54
Q

How are the reactions of acyl chlorides and acid anhydrides different

A

Acid anhydrides are less vigorous because they produce carboxylic acids , whilst acyl chlorides produce hydrogen chloride gas

55
Q

What do acid anhydrides react with

A

Water
Ammonia
Alcohol
Primary amine

56
Q

What’s the reaction between an acid anhydrides and water

A

Acid anhydride + water => carboxylic acid + carboxylic acid

57
Q

What’s the reaction between acid anhydrides and ammonia

A

Acid anhydrides + ammonia => amide + carboxylic acid

58
Q

What’s the reaction between acid anhydrides and an alcohol

A

Acid anhydrides + alcohol => esters + carboxylic acids

59
Q

What’s the reaction between acid anhydrides and a primary amine

A

Acid anhydrides + primary amine => N- substituted amine + carboxylic acid

60
Q

What happens in acyl chloride reactions

A

Acyl chlorides have a strong delta positive on the carbon which is susceptible to attack from nucleophiles.
They have a strong delta positive as the oxygen and chlorine atoms are electronegative and draw electrons to themselves

61
Q

What is the mechanism called for acyl chloride mechanisms

A

Nucleophilic Addition - elimination

62
Q

What is aspirin

A

An ester

63
Q

How is aspirin made

A

Reacting ethanoic anhydrides or ethanoyl chloride and salicylic acid

64
Q

What’s the reaction to make aspirin

A

Ethanoic anhydride or ethanoyl chloride + salicylic acid => aspirin + ethanoic acid

65
Q

Why is ethanoic anhydride used instead of ethanoyl chloride in making aspirin in industry

A
  • safer as it’s less corrosive
  • safer as it doesn’t produce HCl gas
  • Cheaper
  • safer as it does not react vigorously with water
66
Q

What is reflux

A

A technique that allows strong heating without losing volatile reactants and products
Volatile compounds evaporate and condense and fall back into the flask

67
Q

Why is heating in reflux not done using a naked flame

A

Heating flammable liquids
So we use a water bath or a mantle
It’s safer than using a naked flame

68
Q

When is distillation used

A

When we want to separate substances with different boiling points

69
Q

What if your compound has a lower boiling point than the starting mixture in distillation

A

Heat to the temperature of the boiling point of compound you want to separate .
Collect product in the separate vessel

70
Q

What if your compound has a higher boiling point than the starting mixture in distillation

A

You heat to the temperature of the boiling point of your compound you want to separate . Your compound will remain in the round bottomed flask

71
Q

When’s using distillation useful

A

When you want to extract a chemical before it reacts any further

72
Q

When is redistillation used

A

When we want to purify volatile substances which can be purified further using separation

73
Q

What’s the method of redistillation

A

Collect different substances by monitoring the temperature they boil at and collecting the different liquids as they come out of the condenser

74
Q

What is a separation technique

A

Used to remove impurities that are dissolves in water

75
Q

What’s the method for using separation

A
  • add products from distillation into a separating funnel
  • add water to dissolve soluble impurities and create an aqueous solution
  • after allowing the solution to settle , 2 layers will form
    Top layer = impure product
    Bottom layer = aqueous layer containing water soluble impurities
  • drain aqueous layer off
  • remember to remove the stopper
  • take the impure product from the separating funnel and add to a round bottom flask (purification )
  • add anhydrous Cacl2 (calcium chloride ) .
    This is a dehydrating agent and removes aqueous substances still remaining
  • invert flask and leave for 20-30 minutes
  • filter the solid drying agent to remove
76
Q

What’s the dehydrating agent used in separation and purification

A

CaCl2 calcium chloride

77
Q

What technique is it when you take impure product from separating funnel and add to a roundbottomed flask

A

Purification

78
Q

What is filtration

A

A technique use to separate solids from liquids

79
Q

Why is a vacuum used in filtration

A

Used to help separate the liquid and the solid components thoroughly

80
Q

What’s the method for filtration

A
  • place a filter paper disc in the Büchner funnel and dampen slightly
    to make a seal
  • pour the reaction mixture into the Büchner funnel with the vaccine line on
  • vacuum creates a reduced pressure in the flask and pulls the liquid through .
  • the solid will be left in the Büchner funnel
81
Q

What is recrystallisation

A

A method to purify solids and the solvent chosen is very important

82
Q

What’s the method of recrystallisation

A

1) add just enough hot solvent to allow impure solid to dissolve. This will mean you have a saturated solution of your impure product
2) allow the solution to cool down slowly , crystals will start to form
3) your impurities will remain dissolved in the solution as there is a smaller quantity of them , it takes a lot longer for them to crystallize
4) filter to get your solid purified crystals . Wash with very cold solvent and dry them off

83
Q

What’s choosing a solvent very important in recrystallisation

A

You want your impure solids to dissolve fully in hot solvent but virtually insoluble when it’s cold .
If your substance won’t dissolve in hot solvent and you can’t filter the purified solid if it is soluble in cold solvent

84
Q

Why is measuring the boiling point important

A

Can help to detect impurities

85
Q

How can we find out impurities using boiling points in distillation

A

If we gently heat the sample we can measure the temperature at which it distill at using a thermometer. This is the boiling point
Compare boiling point against data book value
If your boiling point is higher than what is recorded in the data book value it contains impurities

86
Q

How do you know if your sample contains impurities

A

If the boiling point is higher than what is recorded in the data book
Your sample boils over a range of temperature

87
Q

Why may you need to use other analytic techniques to spot impurities of various organic compounds

A

Various compounds have the same boiling points . Need to use other analytic techniques such as mass spectrometry to spot impurities

88
Q

How can the purity of a compound be determined

A

By measuring the melting point

89
Q

What’s the method to determining the purity of a compound

A

1) add a sample of the solid product into a capillary tube and place into the heating element of the melting point apparatus
2) slowly increase temperature until substance starts to melt
3) there is a temperature range from when the solid just starts to melt to when it fully melts
4) compare melting point against data book values
5) if your substance contains impurities the melting point will be lower and the temperature range the substance melts at will be larger

90
Q

EQ : suggest why aqueous ethanol is a suitable solvent when heating the coconut oil with KOH.
Give a safety precaution used when heating the mixture and justify . (3)

A
  • Allow to dissolve both oil and KOH
  • Use a water bath for heating mixture
  • Ethanol is flammable
91
Q

EQ: The crude aspirin can be purified by recrystallisation using hot ethanol ( bp = 78) as the solvent . Describe two important precautions when heating the mixture of ethanol and crude aspirin (2)

A

Precaution 1 :
Use a water bath
Precaution 2:
Heat to temperature below bp

92
Q

EQ : The pure aspirin is filtered under reduced pressure . A small amount of cold ethanol is then poured through the Büchner funnel. Explain the purpose of adding a small amount of cold ethanol. (1)

A

To remove any soluble impurities

Chemistry Year 13 (6 decks)

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