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Module 6- Organic Chemistry > 26 Carbonyls and carboxylic acids > Flashcards

26 Carbonyls and carboxylic acids Flashcards

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1
Q

What is an aldehyde? (1 mark)

A

The C=O group is at the end pf a carbon chain.

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2
Q

What is a ketone? (1 mark)

A

The C=O group is joined to two carbon atoms in the carbon chain.

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3
Q

How is the aldehyde group written in a structural formula? (1 mark)

A

CHO

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4
Q

How is the ketone group written in a structural formula? (1 mark)

A

CO

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5
Q

What is the ending (naming) for an aldehyde? (1 mark)

A

al

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6
Q

What is the ending (naming) for a ketone? (1 mark)

A

one

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7
Q

What aldehyde does the crested auklet bird release during breeding season? (1 mark)

A

Octanal

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8
Q

Do aldehydes undergo oxidation? (1 mark)

A

Yes

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9
Q

Do ketones undergo oxidation? (1 mark)

A

No

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10
Q

What are the reagents and conditions for the oxidation of an aldehyde? (2 marks)

A

Reflux
Potassium dichromate and sulfuric acid or acidified potassium dichromate

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11
Q

What is the product of an aldehyde being oxidised? (1 mark)

A

Carboxylic acid

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12
Q

Do aldehydes and ketones react with nucleophiles, why/why not? (2 marks)

A

Yes
The C=O bond is polar

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13
Q

What reduces aldehydes and ketones? (1 mark)

A

NaBH4 and water

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14
Q

What is a carbonyl compound? (1 mark)

A

A compound which contains a C=O functional group- aldehydes and ketones.

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15
Q

What are aldehydes reduced to? (1 mark)

A

Primary alcohols

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16
Q

What are ketones reduced to? (1 mark)

A

Secondary alcohols

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17
Q

Draw the mechanism of the reaction of propanone with NaBH4 and water. (5 marks)

A
  1. Curly arrow from C=O bond to delta negative oxygen.
  2. Curly arrow from hydride ion (H-) to delta positive carbon.
  3. Curly arrow from negative oxygen to delta positive hydrogen in water in intermediate.
  4. Curly arrow from H-O bond to delta negative oxygen in water.
  5. Correct products, propan-2-ol and OH- ion.
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18
Q

What does the reaction of a carbonyl compound with hydrogen cyanide produce? (1 mark)

A

A hydroxynitrile

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19
Q

Draw the mechanism of the reaction of propanal with hydrogen cyanide. (4 marks)

A
  1. Curly arrow from C=O bond to delta negative oxygen.
  2. Curly arrow from cyanide ion (-CN) to delta positive carbon.
  3. Curly arrow from negative oxygen to positive hydrogen ion.
  4. Correct product, 2-hydroxybutanenitrile.
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20
Q

What is a nucleophile? (1 mark)

A

An electron pair donor.

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21
Q

What does 2,4-DNP short for? (2 marks)

A

2,4- dinitrophenylhydrazine

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22
Q

What is 2,4-DNP used for? (1 mark)

A

To detect the presence of the carbonyl functional groups.

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23
Q

What is a positive result for a carbonyl group, using 2,4,-DNP? (1 mark)

A

Orange precipitate is formed.

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24
Q

Describe the test for aldehydes/ketones. (2 marks)

A

Add 2,4-DNP and a few drops of sulfuric acid/methanol.
Positive result: orange precipitate formed.

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25
Q

What is Tollen’s reagent used for? (1 mark)

A

To test for an aldehyde.

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26
Q

What is the result an aldehyde gives for Tollen’s test? (1 mark)

A

Positive- silver mirror

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27
Q

How is Tollen’s reagent prepared? (3 marks)

A

Add sodium hydroxide to silver nitrate
until a brown precipitate forms.
Add dilute ammonia until the precipitate dissolves.

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28
Q

How can the result of the test for carbonyl compounds (2,4DNP) be used to identify the carbonyl compound? (2 marks)

A

Each precipitate produced has a different melting point,
this can be compared to the known melting points of the derivatives.

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29
Q

Are carboxylic acids soluble in water, why/why not? (2 marks)

A

Yes, because the C=O is polar.

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30
Q

Explain the trend in solubility of carboxylic acids. (2 marks)

A

As number of carbon sin chain increase, solubility decreases
because the non-polar chain has more of an effect on the overall polarity of the molecule.

31
Q

What are dicarboxylic acids? (1 mark)

A

Carboxylic acids that contain two carboxyl groups.

32
Q

What is the ending (name) of a dicarboxylic acid? (1 mark)

A

‘anedioic acid’

33
Q

What is the ion formed from a carboxylic acid called? (1 mark)

A

carboxylate ion

34
Q

Are the boiling points of carboxylic acids higher or lower than similar Mr alcohols? (1 mark)

A

Higher

35
Q

Why are the boiling points of carboxylic acids higher than similar Mr alcohols? (3 marks)

A

Carboxylic acids can form 2 hydrogen bonds between molecules,
whereas alcohols can only form 1 hydrogen bond between molecules.
So more energy is required to overcome these forces.

36
Q

Why are carboxylic acids acidic? (2 marks)

A

The acidic nature of carboxylic acids is due to the relatively high stability of the carboxylate anion which forms from the delocalisation of the negative charge.

37
Q

Fill in the gap:
The more charge can be spread around, the more ___________ an ion becomes.

A

The more charge can be spread around, the more stable an ion becomes.

38
Q

Why are alcohols not acidic? (2 marks)

A

They are very poor at losing H+ ions,
due to there being no way of delocalising the negative charge of the negative ion formed if an alcohol lost an H+ ion.

39
Q

metal + carboxylic acid –>
(2 marks)

A

H2 and carboxylate salt

40
Q

metal oxide + carboxylic acid –>
(2 marks)

A

water + carboxylate salt

41
Q

alkali + carboxylic acid –>
(2 marks)

A

water + carboxylate salt

42
Q

carbonate + carboxylic acid –>
(2 marks)

A

CO2 + water + carboxylate salt

43
Q

What is the functional group of an ester? (1 mark)

A

COO

44
Q

What is the functional group of an acyl chloride? (1 mark)

A

COCl

45
Q

What is the structural formula of ethanoic anydride? (2 marks)

A

(CH3CO)2O

46
Q

What is esterfication? (2 marks)

A

When alcohol and a carboxylic acid react to produce an ester and water.

47
Q

What is produced when an acyl chloride and alcohol react? (2 marks)

A

An ester and HCl

48
Q

What is produced when an acid anhydride and alcohol react? (2 marks)

A

An ester and a carboxylic acid.

49
Q

What is produced when an acyl chloride and phenol react? (2 marks)

A

A phenyl ester and HCl

50
Q

How are acid anhydrides formed? (2 marks)

A

Condensation reaction
between 2 carboxylic acid molecules.

51
Q

What are the reagents and conditions for esterification? (2 marks)

A

alcohol is warmed
sulfuric acid catalyst

52
Q

Esters can be hydrolysed by an aqueous _____ or a ______.
(1 mark)

A

Acid or a base

53
Q

____________ hydrolysis is the opposite of esterification.
(1 mark)

A

Acid hydrolysis is the opposite of esterification.

54
Q

What are the reagents and conditions for the acid hydrolysis of an ester? (2 marks)

A

reflux
dilute aqueous acid

55
Q

What is the equation or the acid hydrolysis of an ester? (3 marks)

A

ester + water –> carboxylic acid + alcohol

56
Q

Is acid hydrolysis reversible? (1 mark)

A

yes

57
Q

Is alkaline hydrolysis reversible? (1 mark)

A

no

58
Q

What are the reagents and conditions for the alkaline hydrolysis of an ester? (2 marks)

A

reflux
aqueous alkali

59
Q

What is the equation or the alkaline hydrolysis of an ester? (3 marks)

A

ester + OH- –> carboxylate ion + alcohol

60
Q

What is the chemical formula of thionyl chloride? (1 mark)

A

SOCl2

61
Q

Describe how an acyl chloride is prepared. (3 marks)

A

Carboxylic acid is reacted with thionyl chloride
to produce an acyl chloride, sulfur dioxide, and hydrochloric acid.
Fractional distillation is used to separate the acyl chloride from any excess acid or thionyl chloride.

62
Q

Once a carboxylic acid has reacted with thionyl chloride, how is the acyl chloride separated from the other products? (1 mark)

A

Fractional distillation

63
Q

What is produced when an acyl chloride and water react? (2 marks)

A

Carboxylic acid and HCl

64
Q

Why must acylation reactions of acyl chlorides be carried out in anhydrous conditions? (2 marks)

A

Acyl chlorides react vigorously with water
releasing HCl fumes, which are corrosive/toxic.

65
Q

What is produced when an acyl chloride reacts with ammonia? (2 marks)

A

Primary amide
Ammonium chloride

66
Q

What is produced when an acyl chloride reacts with an amine? (2 marks)

A

Secondary amide
An ammonium chloride compound

67
Q

What two things can react with acyl chloride to produce an amide? (2 marks)

A

Ammonia
An amine

68
Q

What is produced when an acid anhydride reacts with a phenol? (2 marks)

A

A phenyl ester and carboxylic acid

69
Q

Draw the mechanism of the reaction between ethanoyl chloride and methylamine. (8 marks)

A

Step 1:
1. Curly arrow from lone pair on methylamine to carbon in ethanoyl chloride
2. Curly arrow from double bond to oxygen o oxygen
Step 2:
3. Correct intermediate with positive N
4. Curly arrow from bond to chlorine to chlorine
5. Curly arrow from negative oxygen to bond, reforming the double bond
Step 3:
6. Curly arrow from hydrogen on N to N
7. Curly arrow from a second methylamine molecule to hydrogen ion
Step 4:
8. Correct products:
CH3CONHCH3 and CH3NH3+ Cl-

70
Q

Describe how ethyl propanoate is prepared. (4 marks)

A
  1. Add ethanol and propanoic acid to boiling tube
  2. Add few drops of concentrated sulfuric acid
  3. Heat under reflux
  4. Add sodium carbonate solution
71
Q

What are the reagents and conditions for an alcohol and an acid anhydride to react? (2 marks)

A

Heated under reflux
Anhydrous conditions

72
Q

What are the reagents and conditions for an alcohol an acyl chloride to react? (2 marks)

A

RTP
anhydrous conditions

73
Q

What is used to purify an ester after it has been produced, how does it purify it? (2 marks)

A

Calcium carbonate, removes traces of alcohol.

74
Q

What is the function of sodium carbonate solution in the preparation of an ester? (2 marks)

A

It reacts with the traces of sulfuric acid and alcohol, neutralising them to produce water and soluble salts.

Module 6- Organic Chemistry (5 decks)

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