Aldehydes And Ketones Flashcards

1
Q

What type of group do aldehydes and ketones contain?

A

A carbonyl group

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the difference between the carbonyl groups in aldehydes and ketones

A

• Carbonyl group is located in different positions
• Aldehydes: carbonyl group is at the end of the carbon chain- al
• Ketones: Carbonyl group is in the middle of the carbon chain- one

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What do aldehydes produce when oxidised?

A

Carboxylic acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Why can’t ketones be oxidised

A

They do not have a hydrogen attached to their carbonyl

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What happens to the other compound when an aldehyde is oxidised

A

The other compound is reduced

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Give the two oxidising agents to test for aldehydes and ketones and the product of the reaction

A
  • Tollens reagent: colourless solution of silver nitrate dissolved in aqueous ammonia
  • Tollens reagent is heated in a test tube with an aldehyde, Ag+ ions are reduced to Ag atoms and a silver mirror forms
  • Ketones can’t be oxidised so there’s no colour change
  • Fehling’s solution/benedict’s solution: blue solution of copper (II) ions dissolved in sodium hydroxide
  • Heated with an aldehyde , the copper (II) ions are reduced to a brick-red precipitate of copper (I) oxide
  • With ketones, no precipitate is formed
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What product is formed when aldehydes are reduced?

A

Alcohols

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What product is formed when secondary alcohols are oxidised

A

They form ketones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What reducing agent is used to reduce aldehydes to alcohols

A

NaBH4 (sodium tetrahydridoborate (III) or sodium borohydride

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What type of reaction is the reduction of aldehydes to produce alcohols

A

• Nucleophilic addition reactions
• H- ions acts as a nucleophile and adds on to the s+ carbon atom

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Give the diagram for the reduction of aldehydes to form primary alcohols and ketones to secondary alcohols

A

Check physical flashcards for answers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Give a detailed diagram of how aldehydes are reduced

A

Check physical flashcards for answers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Where do the H- ions and H+ ions come from?

A

• H-: from the reducing agent
• H+: from water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How does potassium cyanide react with carbonyls?

A

By Nucleophilic addition reactions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the product of the reaction of potassium cyanide and carbonyls

A

Hydroxynitriles, molecules with a CN and an OH group

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Give the equation for how potassium cyanide dissociates in water

A

KCN -> K+ + CN-

17
Q

Describe the reaction between potassium cyanide and a carbonyl group (aldehyde). Give the overall equation for an aldehyde and ketone

A
  • The CN- group attacks the partially positive carbon atom and donates a pair of electrons. Both electrons from the double bond transfer to the oxygen
  • H+ ions add to the oxygen to form the hydroxyl group (OH). Acidified KCN is usually used so there’s a source of H+ ions
  • Check physical flashcards for answers
18
Q

Why is potassium cyanide a dangerous chemical to work with and what are some safety measure

A

• Potassium cyanide is an irritant
• Dangerous if ingested or inhaled
• Reacts with moisture to produce hydrogen cyanide- highly toxic gas
•Wear gloves, safety goggles, lab coat, experiment in a fume cupboard

19
Q

Solution X reacts with liquid ketones to form a crystalline solid.

This reaction can be used to identify a ketone if the crystalline solid is separated, purified by recrystallisation, and the melting point is determined.

Describe how the crystalline solid separated and purified

A
  • Filter/decant (pouring off the top content of a mixture/draining the bottom content)
  • Dissolve in minimum volume of hot solvent
  • Cool/leave (to crystallise) and filter (under reduced pressure)
  • Wash with cold solvent/ water and dry with method
20
Q

Why is KCN used instead of HCN in the reaction with propanone

A

HCN is weak

21
Q

Draw the nucleophilic addition-elimination mechanism of a compound with a carbonyl group and halogen group that is being attacked by a alcohol to produce an ester and one to produce a halide

A

Check physical flashcards for answers

22
Q
  • What are the oxidizing species in Tollens reagent
  • What happens to these oxidizing species during the oxidation of carbonyls
  • Write a half equation to represent this change
  • Write an equation to show the reaction that takes place when Tollens reagent is warmed with pentanal
  • Explain if Tollens reagent will produce a silver mirror when added to 3-methylbutanone
A

Check physical flashcards for answers