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AQA A Level Organic Chemistry > 8. Aldehydes and Ketones > Flashcards

8. Aldehydes and Ketones Flashcards

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1
Q

What is the carbonyl group?

A

C double bonded to O

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2
Q

How are aldehydes named?

A

Using the suffix -al

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3
Q

How are ketones named?

A

Using the suffix -one, or the prefix oxo-

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4
Q

What is a primary alcohol oxidised to?

A

Aldehyde → Carboxylic acid

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5
Q

What is a secondary alcohol oxidised to?

A

Ketone

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6
Q

What would a suitable oxidising agent for primary and secondary alcohols be?

A

Acidified potassium dichromate

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7
Q

Why can ketones not be oxidised?

A

There is no hydrogen bonded to the carbonyl group

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8
Q

What is Fehling’s solution?

A

An alkaline solution that contains copper ions, which act as a mild oxidising agent

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9
Q

What happens when Fehling’s solution is mixed with an aldehyde and heated?

A

The aldehyde is oxidised to a carboxylic acid and the blue copper (II) ions are reduced to copper (I) oxide as a brick red precipitate

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10
Q

What is Tollen’s reagent made of?

A

Aqueous solutions of ammonia and silver nitrate

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11
Q

What happens when Tollen’s reagent is mixed with an aldehyde?

A

The aldehyde is oxidised to a carboxylic acid and the silver (I) ions are reduced to metallic silver

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12
Q

How can the oxidation process that produces aldehydes and ketones be reversed?

A

With a strong reducing agent (e.g. sodium tetrahydridoborate or lithium aluminium hydride)

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13
Q

What reducing agents can be used to reduce aldehydes and ketones?

A
  • sodium tetrahydridoborate - NaBH4 (dissolved in water)

* lithium aluminium hydride (LiAlH4) - (dissolved in a non-aqueous solvent such as ethanol)

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14
Q

What do the reducing agents NaBH4 and LiAlH4 provide?

A

The hydride ion (H+) which acts as a nucleophile

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15
Q

In the reduction of aldehydes and ketones, what does the hydride ion from the reducing agent act as?

A

A nucleophile

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16
Q

What is formed when carboxylic acids are reduced?

A

Aldehyde → Primary Alcohol

17
Q

What is formed when ketones are reduced?

A

Secondary alcohols

18
Q

What type of mechanism is the reduction of an aldehyde?

A

Nucleophilic addition

19
Q

What type of mechanism is the reduction of a ketone?

A

Nucleophilic addition

20
Q

What does the addition of cyanide to an aldehyde or ketone form?

A

A hydroxynitrile

21
Q

What kind of mechanism is it when cyanide and an aldehyde/ketone forms a hydroxynitrile?

A

Nucleophilic addition

22
Q

What is the reagent when a hydroxynitrile is formed from an aldehyde/ketone?

A

KCN or NaCN (followed by H2SO4)

23
Q

What is the nucleophile when a hydroxynitrile is formed from an aldehyde/ketone?

A

:CN-

24
Q

Can hydroxynitrile be formed from aldehydes/ketones in a lab?

A

No

25
Q

Why can’t hydroxynitrile be formed from aldehydes/ketones in a lab?

A

HCN is a very toxic gas and high flammable

26
Q

How is HCN stored?

A

It is not stored, by made in situ by mixing KCN and dilute acid

27
Q

What are the equations to show how HCN is produced in situ?

A
  • sulphuric acid: 2KCN(s) + H2SO4 → 2HCN(g) + K2SO4

* hydrochloric acid: KCN(s) + HCl → HCN(g) + KCl

28
Q

If HCN is stored, what is the best way to store it?

A

As a solid

29
Q

Is HCN toxic?

A

Yes

30
Q

In the formation of hydroxynitrile from aldehydes/ketones, when will chiral molecules be formed?

A

When the reactants are aldehydes or unsymmetrical ketones

31
Q

Can the products of the reactions of cyanide with aldehyde/ketones display optical isomerism?

A

Yes - if the reactant is an aldehyde or an unsymmetrical ketone

32
Q

Why do the products aldehydes and unsymmetrical ketones with HCN display optical isomerism?

A

The carbonyl group is planar meaning there is an equal chance that the nucleophile will attack either side of the molecule resulting in a racemate

33
Q

Conditions of oxidation of an aldehyde to carboxylic acid?

A

Warm under reflux

34
Q

Observation for oxidation of an aldehyde to carboxylic acid?

A

Orange to green

35
Q

Conditions for reduction of carbonyl to alcohol?

A

Room temperature

36
Q

Conditions for addition of HCN carbonyl to hydroxynitrile?

A

Room temperature

AQA A Level Organic Chemistry (16 decks)

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