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Chemistry Module 6 Organic Chemistry And Analysis > Chapter 26 Carbonyls And Carboxylic Acids > Flashcards

Chapter 26 Carbonyls And Carboxylic Acids Flashcards

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1
Q

What is the carbonyl functional group?

A

C==O

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2
Q

State the two organic compounds that have the carbonyl functional group

A

Aldehydes
Ketones

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3
Q

Where the carbonyl functional group positioned on an aldehyde?

A

Carbonyl functional group if found on the end of the carbon chain

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4
Q

State the structural formula of an aldehyde

A

CHO

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5
Q

Where is the carbonyl functional group positioned on a ketone?

A

In the middle of the carbon chain

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6
Q

State the structural formula of a ketone

A

CO

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7
Q

Name the carbonyl group which can be oxidised to produce a carboxylic acid

A

Aldehyde

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8
Q

Describe the process of the oxidation of aldehydes

A

Aldehydes can be oxidised to carboxylic acids when refluxed with the oxidising agent acidified potassium dichromate.
This results in a colour change from orange to green

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9
Q

State the equation for the oxidation of propanal

A

CH3CH2CHO + [O] —> CH3CH2COOH

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10
Q

Describe the nature of the C==O double bond

A

The C==O consists of 3 σ bonds resulting from the direct overlap of orbitals and a π bond formed from the sideways overlap of adjacent p orbitals creating a π bond above and below the plane of the Carbon atoms.
This means the C==O has a trigonal plane shape with a bond angle of 120 degrees.
The C==O is polar due to the difference in electronegativity.
Oxygen is slightly negative and Carbon is slightly positive

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11
Q

State the name of the attacker which reacts with aldehydes and ketones

A

Nucleophile

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12
Q

What mechanism do carbonyl compounds carry out?

A

Nucleophilic addition

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13
Q

What is a nucleophile?

A

Electron pair donor

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14
Q

What mechanism do alkenes carry out?

A

Electrophilic addition

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15
Q

State the two types of nucleophilic addition in carbonyl compounds

A

Reduction of the carbonyl compounds
Reaction of carbonyl compounds with Hydrogen cyanide

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16
Q

State the reducing agent required for the reduction of carbonyl compounds

A

Reagent- NaBH4 followed by the addition of water

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17
Q

State the nucleophile needed for the reduction of carbonyl compounds reaction

A

Hydride ion= H-
Sourced from NaBH4

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18
Q

Write the equation for the reduction of propanal

A

CH3CH2CHO + 2[H] —> CH3CH2CH2OH

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19
Q

What is the product for the reduction of an aldehyde?

A

Primary alcohol

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20
Q

What is the product for the reduction of a ketone?

A

Secondary alcohol

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21
Q

Write the equation for the reduction of propanone

A

CH3COCH3 + 2[H] ——> CH3CHOHCH3

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22
Q

State the reagent needed for the nucleophilic addition of hydrogen cyanide

A

Reagent- mixture of H2SO4 and NaCN to provide the hydrogen cyanide in the reaction

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23
Q

Why can HCN not be used directly in the nucleophilic addition mechanism?

A

Toxic

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24
Q

State the product of the nucleophilic addition reaction with HCN?

A

Hydroxynitrile

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25
Q

Why is the nucleophilic addition reaction mechanism of hydrogen cyanide useful?

A

It increases the length of the carbon chain

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26
Q

Describe the process for the nucleophilic addition reaction with NaBH4

A

1- Lone pair of electrons from the hydride ion is attracted to the slightly positive Carbon atom in the C==O
2- A dative covalent bond is formed between the H- ion and the Carbon atom of the C==O
3- The π bond of the C==O breaks by heterolytic fission forming a negatively charged intermediate
4- The oxygen atom of the intermediate donates a pair of electrons to the H atom of water.
A hydroxide ion is also formed

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27
Q

Describe the nucleophilic addition reaction with NaCN/ H+

A

1- The lone pair of electrons from the CN- ion is attracted to the slightly positive carbon atom in the C==O so a dative bond forms
2- The π bond in the C==O breaks by heterolytic fission forming a negatively charged intermediate
3- The intermediate donates a pair of electrons to a hydrogen ion to form the product
The product is a hydroxynitrile

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28
Q

What reagent is used to test for carbonyl compounds?

A

2,4-DNP detected the C==O in aldehydes and ketones

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29
Q

Describe the process used to test for carbonyl compounds

A

-React organic substance with 2,4-DNP
-The result of an orange ppt indicates a carbonyl compound (aldehyde or ketone)
-Filter and dry ppt
-Determine the melting point of the purified derivative
-Compare the melting point to known data values

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30
Q

What is the positive result when testing for 2,4-DNP?

A

Orange ppt

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31
Q

How can aldehydes and ketones be distinguished from one another?

A

Using Tollens reagent- ammoniacal silver nitrate which indicates the presence of aldehydes

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32
Q

Describe the process of testing for an aldehyde

A

-Add Tollens reagent to the organic substance
- Put the substance into a water bath to 50 degrees
- A silver mirror confirms the presence of an aldehyde

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33
Q

What substance is being reduced when testing for aldehydes?

A

Silver

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34
Q

Write the reduction equation of silver when testing for aldehydes

A

Ag^+ (aq) + e- —-> Ag (s)

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35
Q

What substance is oxidised when testing for aldehydes?

A

Aldehyde

36
Q

Write the equation for the oxidation of the aldehyde when testing for aldehydes

A

-CHO + [O] —> -COOH

37
Q

Describe the process of making Tollens reagent

A

-Aqueous NaOH is added to aqueous silver nitrate until a brown precipitate of silver oxide is observed
-Dilute aqueous ammonia is then added until the precipitate just dissolves

38
Q

State the functional group for a carboxylic acid

A

-COOH

39
Q

Describe how the boiling point increases as chain length increases

A

As chain length increases, the boiling point increases because there are more London forces which require more energy to be overcome.
As branching increases in carboxylic acids, the boiling point decreases because there is less surface contact between the molecules meaning the London forces are weaker and require less energy to be overcome.

40
Q

Describe the solubility of carboxylic acids

A

Carboxylic acids are soluble in water and organic solvents because they are able to form hydrogen bonds
However, as the chain length increases the carboxylic acids become less soluble because the long non polar carbon chains have a greater effect on the overall polarity of the molecule.

41
Q

How can carboxylic acids react?

A

-With metals during redox reactions
-With metal oxides, metal hydroxides and carbonates during neutralisation reactions

42
Q

How do carboxylic acids react with metals?

A

Carboxylic acid + metal —-> carboxylate salt + hydrogen

43
Q

State the equation for the redox reaction of propanoic acid and Ca

A

2CH3CH2COOH + Ca —-> (CH3CH2COO-)2Ca2+ + H2
H is reduced from +1 in propanoic acid to 0 in H2
Ca is oxidised from 0 in Ca to +2 in Calcium propanoate

44
Q

How do carboxylic acids react with metal oxides?

A

Carboxylic acids + metal oxide —-> carboxylate salt + water

45
Q

State the equation for the neutralisation reaction between ethanoic acid and potassium oxide

A

2CH3COOH + K2O ——> 2CH3COO-K+ + H2O

46
Q

State what would be observed in the neutralisation reaction between a carboxylic acid and metal oxide

A

Observe the metal oxide dissolving

47
Q

How do carboxylic acids react with metal hydroxides ?

A

Carboxylic acid + metal hydroxide —-> carboxylate salt + water

48
Q

State the equation for the reaction of methanoic acid and Magnesium hydroxide

A

2HCOOH + Mg(OH)2 —-> (HCOO-)Mg2+ + 2H2O

49
Q

State what would be observed in the neutralisation reaction between a carboxylic acid and metal hydroxide?

A

The metal hydroxide solid would dissolve

50
Q

State what would be observed in the redox reaction between a carboxylic acid and metal

A

Metal dissolving
Bubbles of hydrogen gas forming

51
Q

How do carboxylic acids react with carbonates?

A

Carboxylic acid + carbonate ——> carboxylate salt + carbon dioxide + water

52
Q

State the equation for the neutralisation reaction between butanoic acid and sodium carbonate

A

2CH3CH2CH2COOH + Na2CO3 —> 2CH3CH2CH2COO-Na+ + CO2 + H2O

53
Q

State what would be observed in the neutralisation reaction between a carboxylic acid and metal carbonate

A

The solid metal carbonate would dissolve
Bubbles of CO2 would be produced

54
Q

What is the test for the carboxyl group?

A

Reacting with a carbonate is used to test for the carboxyl group
If a carbonate added to a carboxylic acid, effervescence of CO2 produced

55
Q

What are esters?

A

Derivatives of carboxylic acids where the hydroxyl hydrogen is replaced with an alkyl group

56
Q

How are esters named?

A

The alcohol is named first, then the carboxylic acid
Suffix: -oate

57
Q

State the ways in which esters can be made using esterification

A

-Carboxylic acid and alcohol
-Acid anhydride and alcohol
-Acyl chloride and alcohol

58
Q

State the conditions needed to make an ester using a carboxylic acid and alcohol

A

Concentrated H2SO4 and heated under reflux

59
Q

State the equation for the esterification of methanoic acid and propan-1-ol

A

Carboxylic acid + alcohol ⇌ ester + water
HCOOH + CH3CH2CH2OH ⇌ HCOOCH2CH2CH3 + H2O
Forms propyl methanoate

60
Q

State the conditions needed to make an ester using an acid anhydride and alcohol

A

Reflux under dry conditions
The acid anhydride is warmed with the alcohol
No concentrated Sulfuric acid is used
The reaction is not reversible

61
Q

State the equation for the esterification of ethanoic anhydride and ethanol

A

Acid anhydride + alcohol —-> ester + carboxylic acid
(CH3CO)2O + CH3CH2OH —-> CH3COOCH2CH3 + CH3COOH
Forms ethyl ethanoate

62
Q

State the conditions needed to make an ester using acyl chloride and alcohol

A

Reflux under dry conditions

63
Q

State the equation for the esterification of ethanoyl chloride and methanol

A

Acyl chloride + alcohol —> ester + hydrogen chloride
CH3COCl + CH3OH —-> CH3COOCH3 + HCl
Methyl ethanoate formed

64
Q

State two ways that esters can be hydrolysed

A

-Hot aqueous acid
-Hot aqueous alkali

65
Q

What is the acidic hydrolysis of esters?

A

Ester + water ⇌ carboxylic acid + alcohol
Esters are hydrolysed with hot aqueous acid

66
Q

State the equation for the acidic hydrolysis of propyl methanoate

A

HCOOCH2CH2CH3 + H2O ⇌ HCOOH + CH3CH2CH2OH

67
Q

What is the alkali hydrolysis of esters?

A

Ester + metal hydroxide —-> carboxylate salt + alcohol
Esters is hydrolysed with hot aqueous alkali

68
Q

State the equation for the alkaline hydrolysis of propyl methanoate with NaOH

A

HCOOCH2CH2CH3 + NaOH —-> HCOO- Na+ + CH3CH2CH2OH

69
Q

What is an acid anhydride?

A

Two carboxylic acids joined minus a water molecule

70
Q

Draw the general formula of an acid anhydride

A

R
\
C ==O
/
O
\
C==O
/
R

71
Q

How can the R groups of the acid anhydride structure differ?

A

The R groups can be the same or different
If they are the same then the structure is known as a mixed anhydride

72
Q

How is an acid anhydride named?

A

Using the first name of the carboxylic acid(s) present then anhydride

73
Q

What is acyl chloride?

A

A derivative of a carboxylic acid where the OH is replaced by Cl

74
Q

How are acyl chlorides named?

A

First name is the carboxylic acid
Suffix -oyl chloride

75
Q

How are acyl chlorides made?

A

Reacting carboxylic acids with thionyl chloride, SOCl2
Carboxylic acid + thionyl chloride —> acyl chloride + Sulfur dioxide + hydrogen chloride

76
Q

State the conditions needed to make acyl chlorides

A

Dry

77
Q

State the equation needed to make propanoyl chloride from propanoic acid and thionyl chloride

A

CH3CH2COOH + SOCl2 —-> CH3CH2COCl + SO2 + HCl

78
Q

Explain why conditions must be dry when making acyl chlorides

A

Water must not be present otherwise the acyl chloride produced will react to form a carboxylic acid

79
Q

State the different reactions of acyl chlorides

A

-Be used to make esters including phenyl esters which are not possible with carboxylic acids
-Be used to make carboxylic acids
-Be used to make primary and secondary amides

80
Q

How are acyl chlorides used to make esters?

A

Acyl chloride + alcohol —> ester + hydrogen chloride

81
Q

How are acyl chlorides used to make carboxylic acids?

A

Acyl chloride + water —> carboxylic acid + hydrogen chloride

82
Q

How are acyl chlorides are used to make primary amides?

A

Acyl chloride + ammonia —-> primary amide + hydrogen chloride

83
Q

What are primary amides?

A

Where the N is bonded to one carbon

84
Q

How are acyl chlorides used to make secondary amides?

A

Acyl chloride + amine —> secondary amide + hydrogen chloride

85
Q

What are secondary amides?

A

The Nitrogen is bonded to 2 carbon atoms

Chemistry Module 6 Organic Chemistry And Analysis (2 decks)

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