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Chemistry - Module 6 > 26-Carbonyls And Carboxylic Acids > Flashcards

26-Carbonyls And Carboxylic Acids Flashcards

1
Q

Can you oxidise aldehydes

A

Yes

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2
Q

Product of oxidation of aldehydes

A

Carboxylic acid

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3
Q

Reaction conditions for oxidation of alcohols

A

o Reflux
o Acidified potassium dichromate (H2SO4 (dilute) / K2Cr2O7 )
o Dichromate (VI) ions turn from orange to green

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4
Q

Equation of oxidation of propan-1-ol in excess oxidising agent

A
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5
Q

Can you oxidise Ketones

A

No

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6
Q

Why can’t you oxide ketones

A

• Oxidation = addition of oxygen or loss of hydrogen
o ketones do not have the essential H-group need to be removed (cannot produce the water side product)

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7
Q

How to distinguish between ketones and aldehydes - basic

A

• lack of reactivity is one way to distinguish between aldehydes and ketones

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8
Q

How does the C=O influence reactivity

A
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9
Q

Difference between C=O and C=C

A

• C=C in alkenes is non-polar = reacts via electrophilic addition

• In carbonyls, the e- density lies closer to more electronegative O atom, resulting in a dipole: Cδ+=Oδ- = polar

• Nucleophiles are attracted to (and attack) the slight positive charge on the C atom in carbonyls.

• Aldehydes + ketones can therefore react with some nucleophiles via nucleophilic addition

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10
Q

Reactions of aldehydes

A
  • oxidise to carboxylic acids
  • reduction to primary alcohol
  • formation of hydroxynitrile
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11
Q

Type of reaction between NaBH4 and aldehyde

A

Reduction

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12
Q

NaBH4

A

• Used as a reducing agent to reduce aldehydes and ketones to alcohols

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13
Q

What is NaBH4

A

Sodium tetrahydridoborate (III)

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14
Q

Side products of NaBH4 and aldehyde

A

BH3 and Na salt

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15
Q

Reaction conditions for reduction of aldehyde

A

warmed with aqueous NaBH4 - remember AQUEOUS

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16
Q

Draw reaction of reduction of aldehyde + side products

A
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17
Q

Draw reaction of reduction of aldehyde + side products

A
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18
Q

Nucleophilic Addition Mechanism for aldehydes and ketones:

A
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19
Q

Reaction of ketones

A
  • reduction to form secondary alcohols
  • formation of hydroxynitriles - HCN
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20
Q

Why is the reaction between HCN and aldehyde/ketone important

A

increases length of a carbon chain

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21
Q

Reaction conditions between HCN and ketone / aldehyde

A

H2SO4 and NaCN

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22
Q

What type of reactions is aldehyde / ketone with HCN

A

Nucleophilic addition

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23
Q

Why don’t we use HCN by itself

A

colourless + extremely poisonous liquid that boils slightly above room temp. Cannot be safely used in the lab

NaCN and sulfuric acid are used instead to generate the HCN in the reaction

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24
Q

Draw overall reaction for propanal and HCN

A
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25
Q

Nucleophilic Addition Mechanism for propanal and HCN

A
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26
Q

Nucleophilic Addition Mechanism for propanal and HCN - what is the nucleophile

A

:-CN

Lone pair + negative charge on the carbon!!

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27
Q

How to detect carbonyl compounds in BOTH aldehydes and ketones

A

Use Brady’s reagent

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28
Q

What is Brady’s reagent

A

2,4 – dinitrophenylhydrazine (2,4-DNP/2,4-DNPH) dissolved in methanol and sulfuric acid

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29
Q

Colour change of Brady’s reagent

A

• Brady’s reagent = pale orange solution
• In the presence of carbonyl group: yellow/orange precipitate

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30
Q

What is the precipitate formed in positive Brady’s reagent

A

2,4-dinitrophenylhydrazone

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31
Q

How to identify 2,4-dinitrophenylhydrazone

A

o Purify the precipitate – filtration (separates solid from solution)
o Solid is recrystallised to form a pure sample
o Melting point is measured and recorded, and compared to a data base.

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32
Q

How to distinguish between aldehyde and ketone

A

Tollens reagent

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33
Q

What is tollens reagent

A

o solution of silver nitrate in aq. ammonia
o colourless

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34
Q

How to use Rollins reagent

A

o warm gently in water bath

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35
Q

Colour change in tollens reagent

A

• In the presence of an aldehyde, a silver mirror (precipitate) is formed.
• Ketones will not react with Tollens’ reagent – remains colourless.

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36
Q

Oxidising agent in tollens

A

Ag+

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37
Q

Reduction + oxidation reaction in tollens

A
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38
Q

Why is -COOH soluble

A

• C=O and O-H bonds both polar
• Can form H-bonds with water
• Carboxylic acids with up to 4 C-ato

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39
Q

Trend in -COOH solubility

A

• Carboxylic acids with up to 4 C-atoms are soluble
• As the number of C-atoms increases, solubility decreases as the non-polar carbon chain has a greater effect on the solubility.
• Dicarboxylic acids are very soluble

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40
Q

Reactions of -COOH

A
  1. Redox reactions occur with metals
  2. Neutralisation reactions occur with bases
    (metal oxides, alkalis and carbonates)
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41
Q

Both neutralisation reactions and redox reactions of -COOH form…

A

carboxylate salts

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42
Q

How to name carboxylate salts

A

ions are named by changing the –ic acid ending to -ate

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43
Q

Redox reaction of -COOH - describe overall

A

• Aqueous carboxylic acids react with metals to form hydrogen gas and a carboxylate salt

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44
Q

Observations of Redox reaction of -COOH

A

o Metal dissolves
o Effervescence

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45
Q

Write reaction between propanoic acid and magnesium - include state symbols

A
46
Q

Neutralisation reaction of -COOH with metal oxides - describe overall

A

• Aqueous carboxylic acids reacts with metal oxides or alkalis to form a carboxylate salt and water

47
Q

Neutralisation reaction of -COOH with carbonates - describe overall

A

• Aqueous carboxylic acids reacts with carbonates to form a carboxylate salt, water and carbon dioxide

48
Q

Observations of neutralisation reaction of -COOH

A

o Metal oxide will dissolve
o Effervescence
o If -COOH is in excess = solid carbonates will dissolve

49
Q

Write reaction for…

Propanoic acid + calcium oxide

Propanoic acid + sodium hydroxide

Propanoic acid + sodium carbonate

A
50
Q

Test for carboxyl group

A

• Aqueous carboxylic acids reacts with carbonates to form a carboxylate salt, water and carbon dioxide
• Carboxylic acids are the only common organic group sufficiently acidic to react with carbonates

51
Q

What’s common between carboxylic acid derivatives

A
52
Q

Draw general structure of ester

A
53
Q

Formation of ester - 2 ways

A

• alcohol + carboxylic acid -> ester + water

• also be formed from acid anhydrides

54
Q

Reaction conditions of alcohol + carboxylic acid

A

warmed with H2SO4 catalyst

55
Q

Draw reaction + name of products of propan-1-ol and Ethanoic acid

A
56
Q

How to name esters

A

• Named after the parent carboxylic acid
-oic acid is replaced with –oate
• The alkyl chain attached to the O (from the alcohol) is added as the first word
(-ol becomes –yl)

57
Q

Name these

A
58
Q

Reaction of esters

A

• Hydrolysis of esters
o Acid + alkaline

59
Q

Process of acid hydrolysis of esters + reaction conditions

A

• Ester is heated under reflux with dilute aqueous acid.

60
Q

Products of acid hydrolysis of ester

A

carboxylic acid and an alcohol

61
Q

Is acid hydrolysis reversible

A

Yes

62
Q

Draw acid hydrolysis of ethyl propanoate

A
63
Q

Process of alkaline hydrolysis of esters + products

A

• Ester is heated under reflux with aqueous hydroxide ions.

64
Q

Products of alkaline hydrolysis of esters

A

carboxylate ion and an alcohol

65
Q

What’s different if NaOH is used in alkaline hydrolysis

A

forms the sodium salt not the ion

66
Q

Is alkaline hydrolysis reversible

A

No - irreversible

67
Q

What happens to the sodium carboxylate salt …

A

needs to get protonated by an acid (such as HCl) to form the carboxylic acid (-COOH)

68
Q

Draw alkaline hydrolysis of ethyl propanoate

A
69
Q

Acid hydrolysis vs alkaline hydrolysis of esters

A
70
Q

General structure of acyl chlorides

A
71
Q

How to form acyl chloride

A

• Parent carboxylic acid reacted with thionyl chloride (SOCl2)
• Products = acyl chloride, SO2 and HCl

72
Q

Reaction conditions for formation of acyl chlorides

A

• Reaction must be carried out in a fume hood

73
Q

Draw reaction scheme for formation of acyl chloride

A
74
Q

How to name acyl chlorides

A

• Named after parent –COOH
• -oic acid and replaced with –oyl chloride

75
Q

Reactions of acyl chlorides + what is the type

A

• addition-elimination reactions:
o Reaction with alcohols and phenols to form esters
o Hydrolysis to form carboxylic acids
o Reaction with ammonia and amines to form amides

76
Q

Reaction between acyl chloride and alcohol

A

Forms an ester

77
Q

Why are acyl chlorides easily converted into -COOH derivatives

A

• Acyl chlorides are extremely reactive; and so are easily converted into –COOH derivatives

78
Q

General equation for acyl chloride + alcohol

A
79
Q

General reaction between acyl chloride + phenol

A
80
Q

Draw reaction between propanol chloride + ethanol

A
81
Q

Draw reaction for propanoic chloride + phenol - bit idk if this is right because it includes the conditions of NaOH and heat which is not what Saunders said

A
82
Q

So conditions of acyl chloride and phenol

A

Possibly NaOH and heat

83
Q

Draw mechanism for reaction of methanoyl chloride and ethanol

A
84
Q

Draw mechanism for reaction of methanoyl chloride and phenol - again reaction conditions?

A
85
Q

Can a carboxylic acid and phenol make an ester

A

• COOH are not reactive enough to form esters with phenols
• Acyl chlorides are much more reactive

86
Q

Formation of carboxylic acid from acyl chlorides - type of reaction

A

Hydrolysis

87
Q

General equation for Hydrolysis of acyl chlorides

A
88
Q

Observations of hydrolysis of acyl chloride

A

• Very vigorous reaction
• Dense, steamy HCl fumes

89
Q

Nucleophile of hydrolysis of acyl chloride

A

Water

90
Q

Draw reaction of hydrolysis of propanoyl chloride

A
91
Q

Draw NUCLEOPHILLIC ADDITION-ELIMINATION mechanism for the reaction between methanoyl chloride and water

A
92
Q

What type of reaction is the Formation of primary amides from acyl chlorides

A

Condensation reaction

93
Q

What happens if you react acyl chloride and ammonia - description

A

• The nitrogen atom in ammonia and amines has a lone pair of electrons which can be used to attack the carbonyl carbon atom in the acyl chlorides

94
Q

Produce of ammonia + acyl chlorides

A

• The product is a primary amide (when reacted with ammonia) or secondary amide (when reacted with primary amines) AND ammonium chloride

95
Q

Draw reaction between ethanoyl chloride and ammonia

A
96
Q

General equation of acyl chloride + ammonia

A
97
Q

Type of reaction for acyl chloride and ammonia

A

Nucleophilic addition - elimination

98
Q

Draw reaction between propanoyl chloride and ammonia

A
99
Q

Draw reaction between propanoyl chloride and methyl amine

A
100
Q

Draw the mechanism for methanoyl chloride and ammonia

A
101
Q

How to make a secondary amide

A

Acyl chloride + primary amine

102
Q

Write general reaction for formation of secondary amide

A
103
Q

Draw reaction between ethanoyl chloride and a primary amine

A
104
Q

What is an acid anhydride

A

two carboxylic acid groups joined together.

105
Q

Reactions of acid anhydrides

A

• React similarly to acyl chlorides with alcohols, phenols, water, ammonia and amines

106
Q

How reactive are acid anhydrides

A

• Less reactive than acyl chlorides = useful

107
Q

Reaction names of acid anhydrides

A
  • esterification - with alcohols
108
Q

Acid anhydride esterification reaction conditions

A

No acid catalyst needed

109
Q

Write AND draw the reaction for acid anhydride and phenol AND name products

A
110
Q

Draw reaction scheme for Ethanoic anhydride and Ethanol

A

Chemistry - Module 6 (5 decks)

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