3.8 Aldehydes and Ketones Flashcards

1
Q

Draw the displayed formula for ethanal.

A

(see page 1 in the chemrevise revision guide)

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2
Q

What is the functional group for an aldehyde?

A

C=O on the end of a chain with an H attached to the chain too.

(see page 1 in the chemrevise revision guide)

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3
Q

Draw the displayed formula for propanone.

A

(see page 1 in the chemrevise revision guide)

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4
Q

What is the functional group for an ketone?

A

If the C=O is in the middle of the chain.

see page 1 in the chemrevise revision guide

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5
Q

What is a carbonyl?

A

Carbonyls are compounds with a C=O bond.

They can be either aldehydes or ketones.

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6
Q

How do carbonyls bond?

A

Intermolecular forces in carbonyls.

Pure carbonyls cannot hydrogen bond, but bond instead by permanent dipole forces.

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7
Q

How soluble are carbonyls in water?

A

The smaller carbonyls are soluble in water because they can form hydrogen bonds with water.

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8
Q

Do carbonyls undergo addition reactions easily?

A

In comparison to the C=C bond in alkenes, the C=O is stronger and does not undergo addition reactions easily.

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9
Q

Are carbonyls polarised?

A

The C=O bond is polarised because O is more electronegative than carbon. The positive carbon atom attracts nucleophiles.

(see page 1 in the chemrevise revision guide)

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10
Q

What is an oxidising agent that causes alcohols and aldehydes to oxidise?

A

potassium dichromate, K2Cr2O7

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11
Q

When a primary alcohol is oxidised what is its functional group change?

A

primary alcohol -> aldehydes

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12
Q

When an aldehyde is oxidised what is its functional group change?

A

aldehyde -> carboxylic acid

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13
Q

When a secondary alcohol is oxidised what is its functional group change?

A

secondary alcohol -> ketone

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14
Q

When a tertiary alcohol is oxidised what is its functional group change?

A

tertiary alcohols do not oxidise.

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15
Q

When a ketone is oxidised what is its functional group change?

A

ketones do not oxidise.

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16
Q

What are the reagents and conditions when oxidising an aldehyde?

A

reagent - potassium dichromate (VI) solution and dilute sulphuric acid.

conditions - heat under reflux

17
Q

Draw the equation when oxidising propanal.

A

(see page 1 in the chemrevise revision guide)

18
Q

For oxidising aldehydes with Tollen’s reagent, what are the:

  • Reagents
  • Conditions
  • Reaction
  • Observation
  • Equation
A

(see page 1 in the chemrevise revision guide)

19
Q

For oxidising aldehydes with Fehling’s solution, what are the:

  • Reagents
  • Conditions
  • Reaction
  • Observation
  • Equation
A

(see page 1 in the chemrevise revision guide)

20
Q

What a 2 reducing agents for carbonyls?

A
  • NaBH4 (sodium tetrhydridoborate)
  • LiSlH4 (lithium tetrahydridoaluminate)

Will reduce carbonyls to alcohols.

21
Q

What is the change in functional group when Aldehydes are reduced?

A

aldehyde -> primary alcohol

22
Q

What is the change in functional group when ketones are reduced?

A

ketone -> secondary alcohol

23
Q

Draw the equation for the reduction of propanal.

A

(see page 2 in the chemrevise revision guide)

24
Q

Draw the equation for the reduction of propanone.

A

(see page 2 in the chemrevise revision guide)

25
Draw the mechanism for the reduction of propanone.
(see page 2 in the chemrevise revision guide)
26
Other than a reducing agent, what is another way carbonyls can be reduced?
Catalytic hydrogenation
27
What are the reagents and conditions for catalytic hydrogenation of carbonyls?
Reagent - hydrogen and nickel catalyst Conditions - high pressure (see page 2 in the chemrevise revision guide for some example equations)
28
When adding hydrogen cyanide to a carbonyl what is: - The change in functional group? - The reagents? - The conditions? - The mechanism?
carbonyl -> hydroxynitrile reagent - sodium cyanide (NaCN) and dilute sulfuric acid. The NaCN supplies the nucleophile CN- ions. The H2SO4 acid supplies H+ ions needed in second step of the mechanism. conditions - room temperature and pressure mechanism - nucleophilic addition
29
Draw the equation of the formation of 2-hydroxy-2-methylpropanenitrile from a carbonyl
(see page 2 in the chemrevise revision guide)
30
Draw the equation of the formation of 2-hydroxypropanenitrile from a carbonyl
(see page 2 in the chemrevise revision guide)
31
Why would you use KCN/ NaCN instead of HCN when forming a hydroxynitrile?
We could use HCN but it is a toxic gas that is difficult to contain. KCN/NaCN are still, however, toxic, because of the cyanide ion.
32
Draw the mechanism for formation of a 2-hydroxypropanenitrile form a carbonyl.
(see page 2 in the chemrevise revision guide)
33
Draw the basic displayed formula of the structure of any hydroxynitrile
(see page 2 in the chemrevise revision guide)
34
How is a racemate formed from a carbonyl? Draw the mechanism reaction.
(see page 3 in the chemrevise revision guide)