Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Chemistry > Carbonyl Compounds > Flashcards

Carbonyl Compounds Flashcards

You may prefer our related Brainscape-certified flashcards:
Periodic Table flashcards Chemistry 101 flashcards AP® Chemistry flashcards Organic Chemistry 101 flashcards
1
Q

What are carbonyl compounds?

A

Organic compounds containing the carbonyl functional group

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

What is the general formula for non-cyclic aliphatic ketones?

A

CnH2nO

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

What is the general formula for non-cyclic aliphatic aldehydes?

A

CnH2nO

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

What is the hybridisation of the C of the carbonyl group and what shape is it?

A

sp2 hybridised, trigonal planar

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

How to name aldehydes?

A

Replace ‘-e’ by ‘-al’

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

How to name ketones?

A

Replace ‘-e’ by ‘-one’

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How does the melting and boiling point of carbonyl compounds compare to alkanes to similar Mr and why?

A

Carbonyl compounds have higher melting and boiling point because more energy is required to overcome the stronger pd-pd between polar molecules of carbonyl compounds compared to the weaker id-id between alkane molecules

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

How does the melting and boiling points of carbonyl compounds compare to alcohols and carboxylic acids of similar Mr and why?

A

Carbonyl compounds have a lower melting and boiling point compared to alcohols and carboxylic acids of similar Mr because less energy is required to overcome the weaker pd-pd between carbonyl molecules than the stronger hydrogen bonds between alcohols or carboxylic acid molecules

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

Are carbonyl compounds soluble in water?

A

-Carbonyl compounds with small Mr are generally soluble in water due to formation of hydrogen bonds with water molecules
- Carbonyl compounds with large Mr are generally insoluble in water due to long non-polar hydrocarbon chains. As the length of hydrocarbon chain increases, there is greater hindrance towards hydrogen bond formation with water molecules

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

How can carbonyl compounds be used as a solvent?

A
  • It can be used as a solvent to dissolve polar solutes by the formation of either hydrogen bonds or pd-pd interactions
  • It can also dissolve non-polar solutes through the formation of id-id between non-polar groups of carbonyl and solute molecules
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the methods of prepare aldehydes?

A

Mild oxidation of primary alcohols to aldehydes

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

What are the conditions for the mild oxidation of primary alcohols to aldehydes?

A

Acidified K2Cr2O7, heat with immediate distillation

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

What is the equation for the mild oxidation of primary alcohols to aldehydes?

A

RCH2OH + [O] → RCHO + H2O

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

How to obtain aldehyde as the major product for the mild oxidation of primary alcohols to aldehydes?

A
  1. Mild oxidising agent is used, K2Cr2O7 used instead of KMnO4
  2. Temperature of reaction mixture is adjusted to below the boiling point of alcohol but above that of aldehyde so as distil out the aldehyde once it is formed and will not be further oxidised to carboxylic acid
  3. Limited amount of oxidising agent used, this lowers the probability of aldehyde being further oxidised into carboxylic acid
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the methods to prepare ketones?

A
  1. Oxidation of secondary alcohols into ketones
  2. Vigorous oxidation of tetra-substituted alkenes
  3. Fridel-craft acylation to give aryl ketones
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the reagents and conditions of the oxidation of secondary alcohols into ketones?

A

acidified K2Cr2O7 (aq) or KMnO4 (aq), heat under reflux

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the equation for the oxidation of secondary alcohols into ketones?

A

CH3CH(OH)CH3 + [O] → CH3COCH3 + H2O

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are the reagents and reagents for the vigorous oxidation of tetra-substituted alkenes to give ketones?

A

acidified KMnO4, heat under reflux

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are the reagents and conditions for fridel-craft acylation to give aryl ketones?

A

RCOCl, anhydrous AlCl3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the reactivity of the carbonyl group like?

A

The electronegative O atom draws the electron density away from the less electronegative C atom, resulting in an electron-deficient C atom. The electron-deficient carbonyl C atom serves as an electrophilic centre for reaction with nucleophilic reagents

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What reactions can carbonyl compounds undergo?

A
  1. Nucleophilic addition
  2. Condensation
  3. Oxidation
  4. Reduction
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What compound do carbonyl compounds undergo condensation reaction with?

A

Compounds containing the -NH2 group

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is the product for the condensation of carbonyl compounds?

A

Imines (compounds with C=N) group

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What reaction is 2,4-DNPH?

A

Condensation reaction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What does 2,4-DNPH test for?

A

Carbonyl compounds (aldehydes and ketones)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is the positive test result for 2,4-DNPH?

A

Yellow/orange ppt.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Does aldehydes and ketones undergo oxidation?

A
  • Aldehydes get oxidised into carboxylic acids
  • aliphatic ketones do not get easily oxidised
  • aryl ketones gets oxidised
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What types of reagents aldehydes can undergo oxidation with?

A
  1. Using KMnO4 or K2Cr2O7’
  2. Tollens’ reagent
  3. Fehling’s reagent
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What are the reagents and conditions for the oxidation of aldehydes using KMnO4 or K2Cr2O7?

A
  • acidifed KMnO4, heat under reflux
  • acidified K2Cr2O7, heat under reflux
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What is the equation for the oxidation of aldehydes using KMnO4 or K2Cr2O7?

A

RCHO + [O] → RCOOH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What is the observation for the oxidation of aldehydes using KMnO4 or K2Cr2O7?

A
  • acidified KMnO4 used: Purple to colourless
  • acidified K2CrO7 used: Orange to green
32
Q

What are the reagents and conditions for the oxidation of aldehydes using Tollens’ reagent?

A

Tollens’ reagent, warm

33
Q

What is the equation for the oxidisation of aldehydes using Tollens’ reagent?

A

RCHO + 2[Ag(NH₃)₂]⁺ + 3OH⁻ → RCOO⁻ + 2Ag (s) + 4NH₃ + 2H₂O

34
Q

What is tollens’ reagent?

A

A mild oxidising agent comprising of AgNO₃ dissolved in NH₃, giving rise to [Ag(NH₃)₂]⁺

35
Q

What is the positive test observation for Tollens’ reagent?

A

Silver mirror (black ppt. of Ag)

36
Q

What reacts with Tollens’ reagent?

A

Aldehydes (both aliphatic and aromatic)
*methanoic acid (HCOOH) also can react

37
Q

What carbonyl compound reacts with KMnO4 or K2Cr2O7?

A
  • Aldehydes (both aliphatic and aromatic)
  • aryl ketones
38
Q

What are the reagents and conditions for the oxidation using Fehling’s reagent?

A

Fehling’s reagent, warm

39
Q

What is the equation for oxidation using Fehling’s reagent?

A

RCHO + 2Cu²⁺ +5OH⁻ → RCOO⁻ + Cu₂O (s) + 3H₂O

40
Q

What is Fehling’s reagent?

A

Mild oxidising agent comprising of copper(II) tartrate in excess NaOH(aq)

41
Q

What is the positive observation for Fehling’s reagent?

A

Brick-red ppt. of Cu₂O

42
Q

What reacts with Fehling’s reagent?

A

aliphatic aldehydes

43
Q

What reagents and conditions are required for the oxidation of aryl ketones?

A

Acidified KMnO4, heat under reflux

44
Q

What is the product of the oxidation of aryl ketone?

A

benzoic acid

45
Q

What are tri-iodomethane test for carbonyl compounds?

A

presence of CH₃CO- group

46
Q

What is the reagents and conditions for tri-iodomethane test?

A

I₂ in NaOH(aq), warm

47
Q

What reaction is tri-iodomethane test?

A

Oxidation

48
Q

What reaction is Tollens’ reagent test?

A

Oxidation

49
Q

What reaction is Fehling’s reagent test?

A

Oxidation

50
Q

What is the equation for the tri-iodomethane test for carbonyl compounds?

A

CH₃COR + 3I₂ +4OH⁻ → CHI₃ + RCOO⁻ +3I⁻ + 3H₂O

51
Q

What is the observation for the positive test result of tri-iodomethane test?

A

Pale yellow ppt. (CHI₃) with a characteristic antiseptic smell formed

52
Q

What carbonyl compounds can undergo reduction?

A

Aldehydes and ketones

53
Q

What are the reagents and conditions for reduction for carbonyl compounds?

A
  1. LiAlH₄ in dry ether
  2. H₂ (g), Ni, heat
  3. NaBH₄
54
Q

What will aldehydes get reduced to?

A

Primary alcohol

55
Q

What will ketones get reduced to?

A

Secondary alcohol

56
Q

Why must reactions with LiAlH₄ be carried out in dry conditions?

A

LiAlH₄ can reduce water explosively to form hydrogen gas
LiAlH₄ + 4H₂O → LiOH + Al(OH)₃ + 4H₂

57
Q

What does LiAlH₄ not reduce and why?

A

LiAlH₄ does not reduce alkenes because the electron rich C=C bond in alkenes repel the AlH₄⁻ nucleophile

58
Q

What does NaBH₄ reduce and not reduce?

A

NaBH₄ reduce aldehydes and ketones but not esters, amides or carboxylic acids

59
Q

How to test for carbonyl compounds (aldehydes and ketones)?

A

Test: 2,4-DNPH
Positive test result: Yellow/orange ppt. formed

60
Q

Hot to distinguish between aldehydes and ketones?

A
  1. Fehling’s reagent, warm
    - positive (aliphatic aldehydes): brick-red ppt. of Cu₂O formed
  2. Tollens’ reagent, warm
    - positive (aldehydes): Silver mirror/black ppt. of Ag formed
  3. acidified K2Cr2O7, heat or acidified KMnO4, heat (aldehydes and aryl ketones)
61
Q

How to distinguish between aliphatic and aromatic aldehydes?

A

Use Fehling’s reagent, warm
Positive (brick-red ppt. of Cu₂O): aliphatic aldehyde

62
Q

How to identify methyl carbonyl compounds?

A

tri-iodomethane test
warm with I₂, NaOH (aq)

63
Q

What are the reagents and conditions of nucleophilic addition of HCN with carbonyl compounds?

A
  • HCN, small amount of NaOH (aq)/KOH (aq) or
    HCN, small amount of NaCN (aq)/KCN (aq)
64
Q

What is the equation of nucleophilic addition of HCN for aldehydes?

A
  1. Initial generation of nucleophile:
    - NaOH or KOH used:
    HCN + OH⁻ → CN⁻ + H₂O
    - NaCN or KCN used:
    NaCN → Na⁺ + CN⁻
  2. RCHO + HCN → RCH(OH)CN
65
Q

What is the equation of nucleophilic addition of HCN for ketones?

A
  1. Initial generation of nucleophile:
    - NaOH or KOH used:
    HCN + OH⁻ → CN⁻ + H₂O
    - NaCN or KCN used:
    NaCN → Na⁺ + CN⁻
  2. RCOR’ + HCN → RC(OH)CNR’
66
Q

What is the use of adding NaOH in nucleophilic addition of HCN and how does it work?

A
  • Reaction is very slow if only HCN is used, the addition of small amount of base increases the rate of reaction
  • HCN ⇌ H⁺ + CN⁻
  • HCN is a weak acid and only undergoes partial ionisation hence equilibrium lies largely to the left
  • The addition of a small amount of base, NaOH, reacts away H⁺, shifting POE to the right, increasing initial [CN⁻] to act as nucleophile
67
Q

What is the use of adding NaCN or KCN in nucleophilic addition of HCN and how does it work?

A

The addition of small amount of NaCN or KCN with HCN provides the CN⁻ used in step 1

68
Q

What does NaOH or KOH act as in the nucleophilic addition of HCN?

A

Base

69
Q

What does NaCN or KCN act as in the nucleophilic addition of HCN?

A

Catalyst as it is regenerated

70
Q

How to prepare HCN?

A

Produce HCN in situ by adding a small amount of H2SO4 to aqueous KCN or NaCN at 10-20 degree celsius

71
Q

Are aldehydes or ketones more reactive towards nucleophilic addition and why?

A

Aldehydes are more reactive than ketones towards nucleophilic addition
1. Inductive effect by alkyl groups: the presence of more electron-donating alkyl groups makes the carbonyl carbon less electron deficient, reducing the likelihood of attack by a nucleophile
2. Steric effects: bulky groups directly bonded to the carbonyl carbon hinder the nucleophile from approaching the electron-deficient carbonyl carbon

72
Q

What is the relative reactivity of carbonyl compounds?

A

methanal (formaldehyde) > aldehyde > ketone

73
Q

What is the order of carbonyl compounds of increasing inductive effect?

A

methanal (formaldehyde) > aldehyde > ketone

74
Q

Are aromatic or aliphatic carbonyl compounds more reactive?

A

Aromatic carbonyl compounds are less reactive due to the resonance effect contributed by aromatic ring

75
Q

Can carbonyl compounds form a racemic mixture, if so, how?

A
  • Carbonyl carbon is sp2 hybridised, there is a trigonal planar arrangement about the carbonyl carbon, allowing nucleophilic attack to take place above and below the plane
  • if the starting carbonyl compound can be converted into a chiral compound by nucleophilic addition of HCN, a racemic mixture will be formed as there is equal probability of attack from either the top or bottom of the plane

Chemistry (21 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions