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Organic chemsitry > Aldehydes and ketones > Flashcards

Aldehydes and ketones Flashcards

1
Q

Can ketones be oxidised?

A

No.

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2
Q

Can aldehydes be oxidised?

A

Yes.

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3
Q

What are aldehydes oxidised into?

A

Carboxylic acids.

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4
Q

Describe how to make Tollens reagent.

A
  1. put silver nitrate solution in a test tube (colourless)
  2. add sodium hydroxide (brown precipitate)
  3. add dilute ammonia until precipitate dissolves
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5
Q

Describe how to test for an aldehyde using Tollens reagent.

A
  1. add substance to Tollens reagent in test tube
  2. put test tube in hot water bath
  3. if aldehyde, silver mirror will form
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6
Q

What happens to the Ag+ ions in Tollens reaction?

A

Reduced to Ag atoms.

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7
Q

Why is a bunsen burner not used in the tests for aldehydes and ketones?

A

They are flammable.

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8
Q

Describe how to test for aldehydes using Fehlings solution.

A
  1. add substance to Fehlings solution in test tube
  2. place in hot water bath
  3. if aldehyde, brick red precipitate formed
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9
Q

What happens to the Cu2+ ions in Fehlings reaction?

A

Reduced to CuO.

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10
Q

Can aldehydes be reduced?

A

Yes.

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11
Q

Can ketones be reduced?

A

Yes.

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12
Q

What are aldehydes and ketones reduced to?

A

Alcohols.

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13
Q

What reducing agent is commonly used?

A

NaBH4 dissolved in methanol and water.

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14
Q

What type of alcohols do aldehydes reduce to?

A

Primary.

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15
Q

What type of alcohols do ketones reduce to?

A

Secondary.

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16
Q

What is the nucleophile in the reduction and where does it come from?

A

H- ion, from reducing agent.

17
Q

Draw the mechanism for the reduction of an aldehyde.

A

…

18
Q

Where does the H+ come from in the reduction mechanism?

A

The acid/water added to the reducing agent at the start.

19
Q

What is the name of the reduction mechanism of aldehydes and ketones?

A

Nucleophillic addition.

20
Q

What is the product of potassium cyanide + carbonyl compound?

A

Hydroxynitrile.

21
Q

What is the name of the mechanism of KCN + carbonyl compoud?

A

Nucleophillic addition.

22
Q

What form is the KCN in for the reaction?

A

Dissolved in acidic solution.

23
Q

Draw the mechanism for the reaction of KCN and an aldehyde.

A

…

24
Q

What is the overall reaction for aldehyde + KCN?

A

RCHO + KCN + H+ → RCH(OH)CN + K+

25
Q

What is the overall reaction for ketone + KCN?

A

RCOR’ + KCN + H+ → RCR’(OH)CN + K+

26
Q

What is formed if an unsymmetrical aldehyde/ketone is used?

A

A mixture of enantiomers.

27
Q

What are the risks with using KCN?

A

*irritant
*dangerous if ingested/inhaled
*forms toxic gas (HCN) when reacts with moisture

28
Q

What are some things that should be done when working with KCN?

A

*wear gloves, goggles, lab coat
*use fume cupbaord

Organic chemsitry (13 decks)

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