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Organic Chemistry > Carboxylic Acids > Flashcards

Carboxylic Acids Flashcards

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1
Q

What is the functional group of a carboxylic acid?

A

-COOH

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2
Q

How are carboxylic acids formed?

A

Oxidising primary alcohols under reflux

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3
Q

Which carboxylic acids are more soluble?

Why?

A

Those with a lower Mr

The -COOH forms hydrogen bonds with water

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4
Q

Why are carboxylic acids only weak acids?

A

They only slightly dissociate in water

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5
Q

How is a carboxylate ion formed?

A

The carbonyl group attracts e- away from the -OH group which leads to the -OH bond being weakened so a proton is easily lost

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6
Q

Why are alcohols not acidic?

A

The -OH bond does not easily break

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7
Q

How does adding a halogen to a carboxylic acid affect the pH?

Eg chloroethanoic acid

A

Chlorine atom is more electronegative so withdraws e- density away from the carbonyl carbon. This causes the O-H bond to become more polar and weaken.
More H+ is therefore released, decreasing the pH

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8
Q

What is more acidic: ethanoic acid or chloroethanoic acid

Why?

A

chloroethanoic acid

Cl pulls e- towards itself

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9
Q

How are acyl chlorides formed?

A

The -OH group of the carboxylic acid is replaced by a chlorine atom

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10
Q

Why is the carbon atom in acyl chlorides readily attacked by nucleophiles?

A

Cl and O are more electronegative than C so the C atom is delta positive

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11
Q

How are acyl chlorides named?

A

It is derived from their corresponding carboxylic acid

Eg ethanoic acid forms ethanoyl Chloride

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12
Q

When there is an -OH in the middle of a carbon chain, how can you refer to it in the name?

A

With ‘hydroxy’

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13
Q

How to form acid anhydrides from carboxylic acids?

A

-OH group is replaced by -OCOR

When two molecules of carboxylic acids join with the elimination of water

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14
Q

How do you name an acid anhydride?

A

The suffix -anhydride replaces the -acid suffix at the end of the carboxylic acid name

If the two C chains are different, write them in alphabetical order

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15
Q

What is a good leaving group?

A

A stable species removed during a chemical reaction

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16
Q

What is the leaving group of acyl chlorides?

What is the by product?

A

Cl-

HCl

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17
Q

What is the leaving group of an acid anhydride?

What is the by product?

A

-OCOR

The corresponding carboxylic acid

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18
Q

Name the mechanism and reaction name for acylation

A

Nucleophilic addition elimination

Reduction

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19
Q

Describe nucleophilic addition elimination

A

Nucleophile attacks the delta positive carbon of the carbonyl group forcing the e- to move from the carbonyl bond to the O making an oxyanion

Carbonyl bond remade causing elimination of the leaving group

Nucleophile loses a H+

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20
Q

How are carboxylic acids formed? (3)

A

1) primary alcohols or aldehydes oxidised by acidified potassium dichromate
2) acyl chlorides react with water (nucleophilic addition elimination)
3) acid anhydrides react with water

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21
Q

Test for carboxylic acids

What is formed?

A

Add Sodium carbonate and CO2 is evolved and fizzing is seen

Ionic salts - these are soluble in water

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22
Q

Name of reaction to form an Ester

What are the reactants?

What is the byproduct?

A

Esterification

Carboxylic acid + alcohol with concentrated H2SO4 (or another strong acid) as a catalyst

Water

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23
Q

What is the isomerism linking esters and carboxylic acids?

A

They are functional group isomers

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24
Q

How do you name an Ester?

A

The alkyl chain of the alcohol is the prefix

The second part of the name is derived from the carboxylic acid - -oic is replaced with -oate

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25
Q

What are the 3 ways to form an Ester?

A

Esterification
Acyl Chlorides reacting with alcohols
Acid anhydrides react with alcohols

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26
Q

What is the name for the formation of esters from acyl chlorides?

A

Nucleophilic addition elimination

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27
Q

What is esterification?

A

Mixing a carboxylic acid and an alcohol in the presence of a concentrated H2SO4 catalyst to form an Ester and water

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28
Q

What is a base added after the formation of an Ester from acyl chlorides?

A

To neutralise HCl

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29
Q

Why are acyl chlorides preferred to carboxylic acids in the formation of esters?

A

No acid catalyst required
Purer product
Yield of Ester is higher as acyl chloride reaction is not reversible

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30
Q

What is the mechanism to form an Ester from alcohols and acid anhydrides?

What is formed?

A

Nucleophilic addition elimination

An Ester and a carboxylic acid

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31
Q

What is the most preferable way to form esters?

Why?

A

From acid anhydrides

Acid anhydrides are cheaper
They react less exothermically so it is less dangerous
Acid anhydrides are less vulnerable to hydrolysis
No corrosive HCl is formed

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32
Q

What is a major use of ethanoic anhydride?

Why is this used over ethanoyl Chloride ?

A

In aspirin

Ethanoic anhydride is cheaper, less corrosive, less vulnerable to hydrolysis, and less dangerous to use

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33
Q

What is the method for the re-crystallisation of crude product?

A

Dissolve sample in a minimum amount of hot solvent
Filter hot
Cool filtrate in a beaker placed in an ice bath
Filter sample using a Büchner funnel
Wash thoroughly to remove any SOLUBLE product
Alllow product to dry

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34
Q

Why do you dissolve the sample in a minimum amount of hot solvent when filtering under pressure/ during recrystallisation?

A

To Create a saturated solution and increase the yield

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35
Q

Why do you filter hot during recrystallising?

A

To prevent recrystallisation whilst filtering and to remove insoluble impurities

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36
Q

Why do you cool the filtrate during recrystallisation?

A

To increase amount of crystals formed

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37
Q

What is the method to test the melting point of the final product of recrystallisation of a crude product?

A

Use melting point apparatus provided to heat sample gently
Heat slowly close to melting point of aspirin
If aspirin is pure the sample should melt over 1-2 degrees and should have a melting point close to data book value
Impurities will cause melting point to be lower and have a larger range

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38
Q

Describe apparatus for filtering under pressure

A

Wide funnel, with horizontal filter paper, going into sealed Büchner funnel
Arm going off to the side leading to a vacuum pump

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39
Q

What is hydrolysis?

A

Breaking up a molecule with H2O or another small molecule

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40
Q

What is hydration?

A

Addition of water

41
Q

What is dehydration?

A

Elimination of water

42
Q

What is hydrogenation?

A

Addition of hydrogen

43
Q

What is the reverse of esterification?

Describe

A

The hydrolysis of an Ester

Ester is hydrolysed back to their carboxylic acid and alcohol groups using water and dilute sulphuric acid catalyst

44
Q

The hydrolysis of an Ester is a reversible reaction. How do you make the hydrolysis as complete as possible?

A

Add an excess of water

45
Q

What occurs when an Ester is heated with an alkali?

What are the 2 mains steps to finally form a carboxylic acid?

A

It is hydrolysed to an alcohol and a carboxylate salt

Add NaOH to form carboxylate salt
Add acid (dilute H2SO4) to form a carboxylic acid
46
Q

Why can’t you draw a line between

CH3COO- and Na+?

A

It is an ionic bond (not covalent) so you have to write them next to each other with their charges showing

47
Q

What is a triglyceride?

Where do they occur?

A

A triester of long chain carboxylic acids (fatty acids) and propane-1,2,3-triol

In fats and oils

48
Q

How can triesters be hydrolysed?

A

Using HOT NaOH to form glycerol and the sodium salts of long chain carboxylic acids

49
Q

What can sodium carboxylate salts be used for?

A

Soap

50
Q

Why is glycerol useful and for what?

A

Is has 2 -OH bonds so forms hydrogen bonds very easily in water

Cosmetics, food, wine, glues (to prevent materials drying too fast)

51
Q

How to remember that sodium carboxylate salts make soap?

A

Sibilance: “Sodium SaltS = SoapS”

52
Q

What is a biofuel?

A

A fuel produced from renewable biological sources

53
Q

What does an Ester + CH3OH (methanol) —>?

A

Methylester + alcohol

54
Q

Define biodiesel

A

Liquid fuel consisting of a mixture of methyl esters of long-chain carboxylic acids from vegetable oils

55
Q

What is a possible solution to our reliance on crude oil?

A

Biodiesel- a renewable fuel formed from crops eg rape seed

Rape seed oil is a triglyceride Ester

56
Q

How do you make biodiesel from rape seed oil?

A

React it with methanol (and a strong acid or alkali as a catalyst) to form a mixture of methyl esters

57
Q

Give the key features of bioethanol

A

Raw materials: sugar cane
Made via fermentation
Used as a mixture with petrol for cars
Increasingly available in the UK

58
Q

Give the key features of biodiesel

A

Made from vegetable oil in a reaction with methanol
Used in cars, buses etc as a mixture with diesel
Can be home made and available at some petrol stations

59
Q

How are amides named?

A

With the suffix -anamide

Eg propanamide

60
Q

2 ways to form an amide

A

Acyl chlorides with NH3

Acid anhydrides with NH3

61
Q

What is the functional group of amides?

A

R-C=O
|
NH2

62
Q

Why is an excess of NH3 used in reaction of acyl chlorides with ammonia?

Name the mechanism and conditions for this mechanism

A

To neutralise HCl

Nucleophilic addition elimination

63
Q

Mechanism for acid anhydride with NH3

A

Nucleophilic addition elimination

64
Q

Functional group for N-Substituted Amides

A 
R-C=O
     |
    N-H 
     |
     R
65
Q

How do you name an N-Substituted Amide?

A

Using an N-alkyl prefix to indicate alkyl group attached to N only and the suffix “-anamide” to indicate length of C chain attached to carbonyl

Eg N-propyl ethanomide

66
Q

How to form N-Substituted Amides using amines

A

React an acyl chloride or an acid anhydride with an amine

Nucleophilic addition elimination

67
Q

What is a biofuel?

A

A fuel produced from renewable biological sources

68
Q

What does an Ester + CH3OH (methanol) —>?

A

Methylester + alcohol

69
Q

Define biodiesel

A

Liquid fuel consisting of a mixture of methyl esters of long-chain carboxylic acids from vegetable oils

70
Q

What is a possible solution to our reliance on crude oil?

A

Biodiesel- a renewable fuel formed from crops eg rape seed

Rape seed oil is a triglyceride Ester

71
Q

How do you make biodiesel from rape seed oil?

A

React it with methanol (and a strong acid or alkali as a catalyst) to form a mixture of methyl esters

72
Q

Give the key features of bioethanol

A

Raw materials: sugar cane
Made via fermentation
Used as a mixture with petrol for cars
Increasingly available in the UK

73
Q

Give the key features of biodiesel

A

Made from vegetable oil in a reaction with methanol
Used in cars, buses etc as a mixture with diesel
Can be home made and available at some petrol stations

74
Q

How are amides named?

A

With the suffix -anamide

Eg propanamide

75
Q

2 ways to form an amide

A

Acyl chlorides with NH3

Acid anhydrides with NH3

76
Q

What is the functional group of amides?

A

R-C=O
|
NH2

77
Q

Why is an excess of NH3 used in reaction of acyl chlorides with ammonia?

Name the mechanism and conditions for this mechanism

A

To neutralise HCl

Nucleophilic addition elimination

78
Q

Mechanism for acid anhydride with NH3

A

Nucleophilic addition elimination

79
Q

Functional group for N-Substituted Amides

A 
R-C=O
     |
    N-H 
     |
     R
80
Q

How do you name an N-Substituted Amide?

A

Using an N-alkyl prefix to indicate alkyl group attached to N only and the suffix “-anamide” to indicate length of C chain attached to carbonyl

Eg N-propyl ethanomide

81
Q

How to form N-Substituted Amides using amines

A

React an acyl chloride or an acid anhydride with an amine

Nucleophilic addition elimination

82
Q

What is a biofuel?

A

A fuel produced from renewable biological sources

83
Q

What does an Ester + CH3OH (methanol) —>?

A

Methylester + alcohol

84
Q

Define biodiesel

A

Liquid fuel consisting of a mixture of methyl esters of long-chain carboxylic acids from vegetable oils

85
Q

What is a possible solution to our reliance on crude oil?

A

Biodiesel- a renewable fuel formed from crops eg rape seed

Rape seed oil is a triglyceride Ester

86
Q

How do you make biodiesel from rape seed oil?

A

React it with methanol (and a strong acid or alkali as a catalyst) to form a mixture of methyl esters

87
Q

How do you name an N-Substituted Amide?

A

Using an N-alkyl prefix to indicate alkyl group attached to N only and the suffix “-anamide” to indicate length of C chain attached to carbonyl

Eg N-propyl ethanomide

88
Q

How to form N-Substituted Amides using amines

A

React an acyl chloride or an acid anhydride with an amine

Nucleophilic addition elimination

89
Q

Functional group for N-Substituted Amides

A 
R-C=O
     |
    N-H 
     |
     R
90
Q

Mechanism for acid anhydride with NH3

A

Nucleophilic addition elimination

91
Q

Why is an excess of NH3 used in reaction of acyl chlorides with ammonia?

Name the mechanism and conditions for this mechanism

A

To neutralise HCl

Nucleophilic addition elimination

92
Q

What is the functional group of amides?

A

R-C=O
|
NH2

93
Q

2 ways to form an amide

A

Acyl chlorides with NH3

Acid anhydrides with NH3

94
Q

How are amides named?

A

With the suffix -anamide

Eg propanamide

95
Q

Give the key features of biodiesel

A

Made from vegetable oil in a reaction with methanol
Used in cars, buses etc as a mixture with diesel
Can be home made and available at some petrol stations

96
Q

Give the key features of bioethanol

A

Raw materials: sugar cane
Made via fermentation
Used as a mixture with petrol for cars
Increasingly available in the UK

97
Q

What is the functional group of acid anhydrides?

A 
R
 |
C=O
 |
O
 |
C=O
 |
R
98
Q

What is the functional group of esters?

A 
R 
 |
C=O
 |
OR

Organic Chemistry (12 decks)

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