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OCR A A-Level Chemistry > Chapter 26 - Carbonyls and Carboxylic Acids > Flashcards

Chapter 26 - Carbonyls and Carboxylic Acids Flashcards

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1
Q

What is a carbonyl group?

A

C=O

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2
Q

What is an aldehyde?

A

The carbonyl functional group is found at the end of the chain

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3
Q

What is a ketone?

A

The carbonyl group is found in the middle of the chain

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4
Q

Suffix for aldehyde

A

-al

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5
Q

Suffix for ketone

A

-one

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6
Q

What is produced when aldehydes are refluxed with acidified dichromate ions?

A

Carboxylic acids

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7
Q

How do you produce carboxylic acids from aldehydes?

A

Reflux the aldehyde with acidified dichromate ions

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8
Q

What is produced when ketones are refluxed with acidified dichromate ions?

A

No reaction

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9
Q

What two bonds are found in the C=O bond?

A

Sigma and pi bonds

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10
Q

Why do carbonyls not react in the same way as alkenes?

A

The C=O bond is polar

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11
Q

Why do nucleophiles react with carbonyls?

A

There is a positively charged carbon atom

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12
Q

Which compound is used as a reducing agent?

A

NaBH4 - must be heated

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13
Q

What is produced when aldehydes are reduced?

A

Primary alcohols

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14
Q

How are primary alcohols produced?

A

Reduction of aldehydes

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15
Q

What is produced when ketones are reduced?

A

Secondary alcohols

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16
Q

Why is the reaction of carbonyls and HCN useful?

A

It is a way of extending the carbon chain

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17
Q

What conditions are needed for carbonyls to react with HCN?

A

Sodium cyanide and sulphuric acid

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18
Q

Describe the mechanism of the nucleophilic addition of carbonyls with NaBH4

A

The lone electrons from the H- ion is donated to the carbocation
This forms a dative covalent bond
The pi bond breaks by heterolytic fission, forming an intermediary
The oxygen atom of this molecule donates an electron pair to a hydrogen atom in a water molecule
This forms an alcohol

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19
Q

Describe the mechanism of the reaction of carbonyls with NaCN

A

The lone pair of electrons on the CN- is donated to the carbocation of the carbonyl, forming the dative covalent bond
The pi bond in the C=O bond breaks by heterolytic fission
The intermediate donated an electron pair to a hydrogen ion

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20
Q

Which compound is used to identify the a carbonyl group?

A

2,4-DNP

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21
Q

What is the positive test for a carbonyl group?

A

An orange precipitate forms

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22
Q

Which test distinguishes between aldehydes and ketones?

A

Using Tollens’ reagent

23
Q

What will happen when Tollens’ reagent is mixed with an aldehyde?

A

A silver mirror effect is produced

24
Q

What will happen when Tollens’ reagent is mixed with a ketone?

A

No reaction

25
Q

Why are carboxylic acids soluble?

A

The C=O bond and O-H bonds are polar so form hydrogen bonds with water molecules

26
Q

Up to what number of carbon atoms are carboxylic acids soluble?

A

4

27
Q

Why does the solubility of carboxylic acids decrease with increasing chain length?

A

The non-polar carbon chain has a greater effect on solubility than the polar bonds

28
Q

What strength are carboxylic acids?

A

Weak

29
Q

What is produced when carboxylic acids react with metals?

A

Hydrogen gas and the carboxylate salt

30
Q

What is produced when carboxylic acids react with metal oxides?

A

A salt and water

31
Q

What is produced when carboxylic acids react with alkalis?

A

A salt and water

32
Q

What is produced when carboxylic acids react with carbonates?

A

Carbon dioxide, water and a salt

33
Q

How can you test for a carboxylic acid?

A

Add carbonate

Carboxylic acids are the only organic compounds acidic enough to react with them

34
Q

What are the four carboxylic acid derivatives?

A

Ester
Acyl chloride
Acid anhydride
Amide

35
Q

How to name an ester

A

The carboxylic acid becomes the -oate

The alkyl chain attached then becomes the first word

36
Q

How to name an acyl chloride

A

Remove the -oic acid suffix from the carboxylic acid an replace with -oyl chloride

37
Q

What is an acid anhydride?

A

Water is removed from two carboxylic acid molecules

38
Q

Describe the process of esterification

A

An alcohol is warmed with a carboxylic acid

H2SO4 catalyst

39
Q

Ester functional group

A

COO

40
Q

Acyl chloride functional group

A

COCl

41
Q

Amide functional group

A

CONH2

42
Q

Describe the acid hydrolysis of esters

A

Ester is heated under reflux with dilute acid catalyst

Ester is hydrolysed into a carboxylic acid and an alcohol

43
Q

Is acid hydrolysis or alkaline hydrolysis reversible?

A

Acid

44
Q

Describe the alkaline hydrolysis of esters

A

Ester heated under reflux with hydroxide ions (e.g. NaOH)

Alcohol and sodium salt formed

45
Q

What compound is used to make acyl chlorides?

A

SOCl2

46
Q

What two gases are created when an acyl chloride is made?

A

SO2 and HCl

47
Q

How do esters react with nucleophiles?

A

They retain the C=O bond but lose the chloride ion

48
Q

What is produced when acyl chlorides react with alcohols?

A

Esters

49
Q

What is produced when acyl chlorides react with phenols?

A

Phenyl esters

50
Q

Which compound is made when an acyl chloride forms either an ester or carboxylic acid?

A

HCl

51
Q

What is produced when carboxylic acids react with water?

A

Carboxylic acids

52
Q

What is produced when an acyl chloride reacts with ammonia?

A

Primary amide and NH4Cl

53
Q

What is produced when an acyl chloride reacts with an amine?

A

Secondary amide and the chloride salt

OCR A A-Level Chemistry (28 decks)

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