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Chemistry > Chapter 26 - Carbonyls > Flashcards

Chapter 26 - Carbonyls Flashcards

1
Q

What functional group do aldehydes and ketones have ?

A

C=O

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2
Q

Where is the functional group found in aldehydes ?

A
  • Found at the end of a carbon chain.
  • The carbon atom is attached to one or two hydrogen atoms
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3
Q

What is the functional group written as in aldehydes ?

A

CHO

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4
Q

What is the simplest aldehyde ?

A

Methanal AKA formaldehyde

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5
Q

Where is methanal commonly used ?

A

Used in solution to preserve biological specimens

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6
Q

Where is the functional group found in ketones ?

A
  • Found in a carbon chain
  • The functional groups is joined to two carbon atoms in the carbon chain
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7
Q

What is the functional group written as in ketones ?

A

CO

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8
Q

What is the simplest ketone ?

A

Propanone

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9
Q

Where is propanone commonly used ?

A
  • Industrial solvent
  • Nail varnish remover
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10
Q

How can aldehydes be oxidised to carboxylic acids ?

A

Refluxed with acidified potassium dichromate and dilute sulphuric acid

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11
Q

Do ketones undergo oxidation reactions ?

A
  • No they do not
  • The lack of reactivity provides chemists with a way of distinguishing between aldehydes and ketones
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12
Q

What is the difference between a C=C bond in alkenes and the C=O bond in carbonyl compounds ?

A
  • The C=C bond in alkenes is non polar
  • The C=O bond in carbonyl compounds is polar
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13
Q

What is more electronegative in the C=O bond ?

A
  • The oxygen is more electronegative than the carbon
  • This makes the carbon end of the bond slightly positive and the oxygen end slightly negative
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14
Q

Due to the polarity of the C=O bond, what do the aldehydes and ketones react with ?

A

Nucleophiles

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15
Q

What type of mechanisms used for carbonyl compounds ?

A

Nucleophilic addition

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16
Q

What is NaBH4 used for ?

A

It is used as a reducing agent to reduce aldehydes and ketones to alcohols

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17
Q

How is an aldehyde/ketone reduced into an alcohol ?

A

They are usually warmed with NaBH4 in aqueous solution

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18
Q

What is hydrogen cyanide (HCN) ?

A
  • Liquid
  • Colourless
  • Extremely poisonous at room temperature
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19
Q

What does the reaction of a carbonyl compound with HCN allow to happen ?

A

It allows the length of the carbon chain to increase

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20
Q

What does the reaction between an aldehyde and hydrogen cyanide make ?

A

A hydroxynitrile

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21
Q

What is 2,4-DNP used for ?

A

It is used to detect the presence of the carbonyl functional group in both aldehydes and ketones

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22
Q

What is 2,4-DNP also known as ?

A
  • 2,4-dinitrophenylhydrazine
  • Brady’s reagent
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23
Q

What do you expect to form when you add 2,4-DNP in the presence of the carbonyl group ?

A
  • A yellow or orange precipitate
  • Called a 2,4-dinitrophenylhydrazone
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24
Q

In practical work how is 2,4-DNP used ?

A

Dissolved in methanol and sulphuric acid

  • pale orange solution
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25
Q

What are the dangers of using 2,4-DNP ?

A

It can be very hazardous because friction or a sudden blow can cause it to explode

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26
Q

How can we distinguish between an aldehyde and a ketone ?

A

Add Tollen’s reagent

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27
Q

What is Tollen’s reagent ?

A

A solution of silver nitrate in aqueous ammonia

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28
Q

In the presence of an aldehyde group, what does the addition of Tollen’s reagent cause to form ?

A

A silver mirror is produced

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29
Q

What ions does Tollen’s reagent contain ?

A

Ag+ (aq)

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30
Q

What do the Ag+ ions act as ?

A

They act as an oxidising agent in the presence of ammonia

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31
Q

What gets reduced when testing with Tollen’s reagent ?

A

Silver ions are reduced to silver

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32
Q

What gets oxidised when testing with Tollen’s reagent ?

A

The aldehyde is oxidised to a carboxylic acid

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33
Q

What is a carboxylic acid ?

A

A carboxylic acid is an organic acid which contains the carboxyl functional group

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34
Q

What does the carboxyl group contain ?

A

It contains both a carbonyl group and a hydroxyl group

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35
Q

Where can you find carboxylic acids ?

A
  • In medicines
  • Fruit juices
  • Vinegar
  • Rhubarb leaves
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36
Q

What are carboxylic acids used for ?

A

They are used in organic synthesis as starting materials or intermediates in the formation of more useful compounds

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37
Q

Give an example of a carboxylic acid derivative

A
  • Aspirin
  • It can be synthesised from salicylic acid
38
Q

What is the solubility of carboxylic acids like ?

A

Carboxylic acids with up to four carbon atoms are soluble in water

39
Q

Which bonds in a carboxylic acid are polar ?

40
Q

What do the polar bonds in a carboxylic acid allow to happen ?

A

They allow the carboxylic acid to form hydrogen bonds with water molecules

41
Q

Trend in solubility for a carboxylic acid as the chain gets bigger

A

As the number of carbon atoms increases, the solubility decreases as the non polar carbon chain has a greater effect on the overall polarity of the molecule

42
Q

What kind of acids are carboxylic acids ?

A
  • They are weak acids
  • They only partially dissociate in water
43
Q

General equation for the dissociation of a carboxylic acid

A

HCOOH →← H+ + HCOO-

44
Q

What kind of reactions do carboxylic acids take place in ?

A
  • Redox reactions with metals
  • Neutralisation reactions with bases

Bases include alkalis, metal oxides and carbonates

45
Q

What is formed in the reactions of carboxylic acids ?

A

Carboxylate salts

46
Q

What is the carboxylate ion ?

A
  • It is an ion in the salt
  • It is named by changing the -ic acid to -ate
47
Q

What kind of a reaction is a carboxylic acid reacting with a metal ?

A

A redox reaction

48
Q

What is formed when a carboxylic acid reacts with a metal ?

A

Hydrogen gas and the carboxylate salt

49
Q

What would you observe when a carboxylic acid reacts with a metal ?

A

The metal disappearing and effervescence as hydrogen is formed

50
Q

What type of a reaction is the reaction of a carboxylic acid with a base ?

A

A neutralisation reaction

51
Q

What can be classified as a base ?

A
  • Metal oxides
  • Alkalis
  • Carbonates
52
Q

What is formed when a carboxylic acid reacts with a metal oxide ?

A

Salt and water

53
Q

What is formed when a carboxylic acid reacts with an alkali ?

A

Salt and water

54
Q

What would you observe when a carboxylic acid reacts with an alkali ?

A

You may not see a reaction as the two solutions react together to form the salt in an aqueous solution

  • Nothing visible is formed
55
Q

What is formed when a carboxylic acid reacts with a carbonate ?

A

Carbon dioxide gas, water and salt

56
Q

What would you observe when a carboxylic acid reacts with a carbonate ?

A

If the carboxylic acid is in excess a solid carbonate would disappear

57
Q

How can you check for the carboxyl group ?

A
  • React it with sodium carbonate
  • If it reacts with sodium carbonate it has a carboxyl group
  • If it does not, then it is likely to be a phenol as phenols are not acidic enough to react with carbonates
58
Q

What is a derivative of a carboxylic acid ?

A

A compound that can be hydrolysed to form the parent carboxylic acid

59
Q

What is the common sequence of carboxylic acids ?

A
  • They all have an acyl group
  • R-C=O
60
Q

What are the derivatives of carboxylic acids ?

A
  • Ester
  • Acyl chloride
  • Acid anydride
  • Amide
61
Q

How do you name an ester ?

A
  • Remove the -oic acid suffix and replace it with -oate
  • The alkyl chain attached to the oxygen atom of the COO group is then added as the first word in the name
62
Q

How do you name an acyl chloride ?

A

Remove the -oic acid suffix from the parent carboxylic and replace it with -oyl chloride

63
Q

How is an acid anhydride formed ?

A

It is formed by the removal of water from two carboxylic acid molecules

64
Q

What is esterification ?

A

The reaction of an alcohol with a carboxylic acid to form an ester

65
Q

What are the conditions of esterification ?

A

The alcohol is warmed with a carboxylic acid with a small amount of concentrated H2SO4

66
Q

What is the catalyst in esterification ?

A

Concentrated H2SO4

67
Q

What is hydrolysis ?

A

The chemical breakdown of a compound in the presence of water or in aqueous solution

68
Q

How can esters be hydrolysed ?

A

By aqueous acid or alkali

69
Q

What is acid hydrolysis ?

A

The reverse of esterification

70
Q

What has to occur for acid hydrolysis to occur ?

A
  • The ester is heated under reflux with dilute aqueous acid
  • The ester is broken down by water, with the acid acting as a catalyst
71
Q

What are the products of acid hydrolysis ?

A
  • Carboxylic acid
  • Alcohol
72
Q

What is alkaline hydrolysis known as ?

A

Saponification

73
Q

Is alkaline hydrolysis reversible ?

A

No it is irreversible

74
Q

What are the conditions for saponification ?

A

Ester is heated under reflux with any compound that has OH- ions

75
Q

What are the products of saponification ?

A
  • Carboxylate ion
  • Alcohol
76
Q

How can acyl chlorides be prepared ?

A

They can be prepared directly from the parent carboxylic acid by reaction with thionyl chloride (SOCl2)

77
Q

Why is the reaction to form acyl chlorides carried out in a fume cupboard ?

A

This is because the products formed in the reaction, SO2 and HCl, are toxic

78
Q

What is the reactivity of acyl chlorides like ?

A

They are very reactive

79
Q

Why are acyl chlorides useful in organic synthesis ?

A

They can easily be converted into carboxylic acid derivatives with good yields

80
Q

How do acyl chlorides react ?

A

They react with nucleophiles by losing the chloride ion whilst retaining the C=O bond

81
Q

What does the reaction between an acyl chloride and an alcohol form ?

A

They react together to form esters

82
Q

Can carboxylic acids react with esters to form phenols ?

A

No, they are not reactive enough

83
Q

What can react with a phenol to create a phenyl esters ?

A
  • Acyl chlorides
  • Acid anhydrides
84
Q

What happens when water is added to an acyl chloride ?

A

A violent reaction takes place

Forms dense and steamy hydrogen chloride

85
Q

What is formed when water is added to an acyl chloride ? (Hydrolysis)

A
  • Carboxylic acid
  • Hydrogen chloride
86
Q

What can ammonia and amines act as ?

A

Nucleophiles

87
Q

How do ammonia and amines act as nucleophiles ?

A

They donate their lone pair of electrons to an electron deficient species

88
Q

What is formed when ammonia/amines react with acyl chlorides ?

89
Q

What is a primary amide ?

A
  • Formed when ammonia reacts with an acyl chloride
  • The nitrogen atom is attached to one carbon atom
90
Q

What is formed when a primary amine reacts with an acyl chloride ?

A

A secondary amide

91
Q

What is a secondary amide ?

A

The nitrogen is attached to 2 carbon atoms

92
Q

What is the reactivity of acid anhydrides like ?

A

They are less reactive than acyl chlorides

Chemistry (29 decks)

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