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CHEMISTRY > ALDEHYDES AND KETONES > Flashcards

ALDEHYDES AND KETONES Flashcards

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1
Q

What functional group do both aldehydes and ketones have

A

Carbonyl, C=O

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2
Q

What is the difference between an aldehyde and a ketone

A

The positioning of the carbonyl group

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3
Q

Where is the carbonyl group on an aldehyde

A

At an end carbon

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4
Q

Where is the carbonyl group on a ketone

A

On an inner carbon

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5
Q

What do aldehydes end in

A

-al

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6
Q

What do ketones end in

A

-one

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7
Q

How are aldehydes oxidized

A

Readily

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8
Q

How are ketones oxidized

A

They cannot be oxidized

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9
Q

Show the oxidation of both an aldehyde and a ketone

A

…

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10
Q

What test can distinguish between aldehydes and ketones

A

Tollen’s silver mirror test

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11
Q

How is Tollen’s reagent made

A

Silver nitrate is added to a test tube. A few drops of sodium hydroxide is added, forming a pale brown precipitate. Add a few drops of dilute ammonia until the precipitate dissolves.

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12
Q

How do you use Tollen’s to test for aldehydes

A

Add sample to a test tube of Tollen’s reagent, then place in a hot water bath. Observe the formation of a silver mirror on the test tube to confirm the presence of an aldehyde

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13
Q

What is the formula of Tollen’s reagent

A

[Ag(NH3)2]+

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14
Q

Why do we not use a Bunsen flame when doing the silver mirror test

A

Aldehydes and ketones are flammable

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15
Q

What is Tollen’s reagent

A

An oxidizing agent

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16
Q

What other than Tollen’s can be used to test for aldehydes

A

Fehling’s solution

17
Q

What color is fehlings solution and why

A

Blue as it contains cu2+ ions

18
Q

How do you test for aldehydes using fehlings solution

A

Warm it up in the presence of a sample. If aldehydes are present, the solution will go from blue to forming brick red precipitate. If ketones are present, there will be no reaction.

19
Q

What does fehlings solution consist of

A

Cu2+ ions dissolved in sodium hydroxide

20
Q

What reducing agents can be used to reduce aldehydes and ketones

A

Sodium borohydride (NaBH4) or sodium tetrahydridoborate(iii) dissolved in methanol and water

21
Q

What are aldehydes reduced to, and show the reduction formula

A

Primary alcohols

22
Q

What are ketones reduced to, and show the reduction formula

A

Secondary alcohols

23
Q

What does a reducing agent produce to reduce aldehydes and ketones to alcohols

A

Hydride ions

24
Q

Show the mechanism for the reduction of an aldehyde and ketone into an alcohol

A
25
Q

What type of mechanism is the reduction of an aldehyde or ketone

A

Nucleophilic addition

26
Q

Where does the H+ ion come from in the reduction of an aldehyde or ketone to an alcohol

A

The water or acid that was added to the reducing agent at the start

27
Q

What is formed when potassium cyanide reacts with carbonyl compounds such as aldehydes or ketones, and what type of reaction is this

A

Hydroxynitriles are produced, nucleophilic addition

28
Q

How is potassium cyanide used to produce CN- ions

A

When dissolved in acidic solution, it dissociates to form K+ and CN- ions. KCN -> K+ + CN-

29
Q

What can be used as a substitute for potassium cyanide when trying to produce a hyrdoxynitrile from aldehydes or ketones, and how is the preparation of this reaction different

A

Hydrogen cyanide, no acid is required

30
Q

Show the mechanism for the reaction of an aldehyde with potassium cyanide

A
31
Q

What is produced if we used unsymmetrical ketones or aldehydes in the reaction with potassium cyanide

A

A mixture of enantiomers is produced

32
Q

How is hydrogen cyanide produced

A

When potassium cyanide combines with moisture

33
Q

Why is potassium cyanide dangerous

A

It is an irritant and very dangerous if ingested or inhaled

34
Q

What precautions must be taken when using potassium cyanide

A

Wear gloves whilst handling
Use a fume cupboard
Wear a lab coat

35
Q

What is the overall generic equation for the reaction of an aldehyde with potassium cyanide

A

RCHO (aq) + KCN (aq) + H+ (aq) -> RCH(OH)CN(aq) + K+ (aq)

36
Q

What is the overall generic equation for the reaction of a ketone with potassium cyanide

A

RCOR(aq) + KCN(aq) + H+ (aq) -> RCR(OH)CN(aq) + K+(aq)

37
Q

What are aldehydes oxidized into

A

Carboxylic acids

38
Q

Why can enantiomers be formed by nucelophilic addition

A

The carbonyl group is planar, so the nucleophile can attack from above or below the plane of this carbonyl group leading to 2 isomers

CHEMISTRY (2 decks)

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