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Year 2 Chemistry OCR A level > AC8: Carbonyls > Flashcards

AC8: Carbonyls Flashcards

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1
Q

What is the carbonyl group

A

C=O

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2
Q

What are the other functional groups that carbonyl refers to

A

-Aldehydes
- Ketones

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3
Q

What is the short hand way of writing aldehyde

A

-CHO

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4
Q

What do aldehyde compounds name end in

A

-al

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5
Q

What is the short hand way of writing ketone group

A

-CO

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6
Q

What do ketone compounds name end in

A

-one

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7
Q

What is the colour change of the dichromate ions when reduced

A
  • Orange to green
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8
Q

What 2 bonds make up the C=O carbonyl group

A
  • Sigma bond
  • Pi bond
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9
Q

What is the main difference between the C=C double bond and the C=O double bond

A

The C=O double bond is polar because oxygen is much more electronegative than carbon

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10
Q

Are carbonyl groups reactive or unreactive with electrophiles

A

Unreactive

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11
Q

Why do nucelophiles attack the carbonyl group C=O

A

Since the carbon is slightly positive due to the dipole

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12
Q

Why are aldhehydes and ketones polar

A

Because of the higher electronegativity of the oxygen, compared to the carbon

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13
Q

Why are the boiling points for carbonyl compounds higher than alkanes and alkenes of similar size

A

Since the dipoles in carbonyl C=O allows permanent dipole-dipole interactions between molecules which are stronger than London forces

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14
Q

Why do carbonyl compounds have lower boiling points than carboxylic acids and alcohols of similar size

A

Since carbonyls cannot form hydrogen bonds since there is no H bonded to the oxygen

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15
Q

Why are short chain aldehydes and ketones soluble

A

Since the oxygen in the C=O can form hydrogen bonds with other compounds such as water

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16
Q

What is the chemical equation for the reduction of ethanol

A

CH3CHO + 2[H] -> CH3CH2OH

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17
Q

What type of reaction is the reaction with NaBH4 and aldehydes and ketones

A

Reduction reaction

18
Q

What is the name of the mechanism when NaBH4 reacts with an aldehydes or a ketone

A

Nucleophilic addition

19
Q

What is the nucleophile in the compound NaBH4

A

H- (hydride ion)

20
Q

Draw the mechanism for the reaction between ethanal and aqueous, acidified sodium cyanide solution

A

Look in the year 2 notes for answer page 54

21
Q

Draw the mechanism for the reaction between ethanol and NaBH4

A

Look in the year 2 notes for answer page 54

22
Q

Describe the 4 steps in the nucleophilic addition reaction with NaBH4

A
  • The lone pair of electrons from the hydride ion is attracted and donated to the slightly positive carbon atom in the aldehyde or ketone C=O double bond
  • A dative covalent bond is formed between the hydride ion and the carbon atom of the C=O double bond
  • The Pi bond in the C=O double bond breaks by heterolytic fission forming a negatively charged intermediate
  • The oxygen atom of the intermediate donates a lone pair of electrons to a hydrogen atom in a water molecule. The intermediate has then been protonated to form an alcohol
23
Q

How do we get the CN- ion

A

From NaCN and an acid

24
Q

Why cannot we just use the HCN

A

Because it’s a lethally toxic gas

25
Q

How do you get alkene to carbonyl

A

Alkene - alcohol - carbonyl

26
Q

How do you get haloalkane to carbonyl

A

Haloalkane- alcohol - carbonyl

27
Q

How do you get alcohol to hydroxynitrile

A

Alcohol - carbonyl - hydroxynitrile

28
Q

How do you get a hydroxynitrile from a carbonyl

A

Add NaCN and an acid

29
Q

What is added to test for a carbonyl , both aldehyde and ketone

A

2,4- dinitrophenylhydrazine / 2,4 - DNP

30
Q

What is produced when 2,4 -DNP is added to a carbonyl

A

An orange / red solid

31
Q

What can you do with the orange / red solid that is produced after 2,4-DNP is added to a carbonyl

A
  • Recrystallise
  • Then measure the melting point
32
Q

What does measuring the melting point of the recrystallised orange/ red solid formed from reacting 2,4 -DNP with a carbonyl

A

It identifies what carbonyl when you’re given the values of the melting points

33
Q

What is the reagent used to test for aldehydes

A

Tollen’s reagent

34
Q

What does a positive Tollen’s test produce

A

A silver mirror

35
Q

What type of reaction occurs during the Tollens’ test

A

Redox

36
Q

In the Tollens’ test what is oxidised and what is reduced

A

Aldehyde is oxidised
Ag is reduced

37
Q

What is the only carbonyl that the Tollens’ test works for

A

Aldehydes

38
Q

What is Tollens’ reagent

A

A mix of Ag and NH3

39
Q

What is the molecular formula of Tollens’ reagent

A

Ag(NH3)2)

40
Q

What are the conditions when using the Tollens’ test

A

Warm

Year 2 Chemistry OCR A level (9 decks)

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