Testing for Aldehydes and Ketones Flashcards

1
Q

What chemically is tollen’s reagent?

A
  • Contains silver ion complex Ag(NH3)2 +
  • (silver nitrated + aqueous ammonia)
  • Colourless solution
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How does tollen’s reagent work?

A
  • Tests for Aldehydes
  • Gently warmed with aldehyde
  • Aldehyde is oxidised
  • Ag(NH3)2 + ions reduced to solid metallic silver Ag
  • Silver mirror is formed if aldehyde present
  • Ketone, no reaction, cannot be oxidised by tollen’s reagent
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is Fehling’s solution

A
  • Alkaline solution containing Copper (II) ions
  • Blue from Copper (II) ions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How does Fehling’s solution work?

A
  • Tests for aldehydes
  • Aldehyde oxidised
  • Becomes carboxylic acid
  • Cu 2+ ions (blue) reduced to Cu + ions and copper oxide forms (brick red)
  • If ketone reacts, nothing happens, not oxidised, so remains blue
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How can acidified potassium dichromate be used to distinguish between aldehydes and ketones?

A
  • Aldehyde oxidised, orange to green
  • Ketone not oxidised, no colour change
How well did you know this?
1
Not at all
2
3
4
5
Perfectly