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A Chem Finale pt 1. > Unit 4.4 Aldehydes and Ketones > Flashcards

Unit 4.4 Aldehydes and Ketones Flashcards

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1
Q

What can oxidising primary/secondary alcohols give u?

A

Aldehydes or ketones

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2
Q

What’s the oxidising agent used for the oxidisation of primary/secondary alcohols?
(Either one)

A
  • Acidified potassium dichromate (VI)
  • Acidified potassium manganate (VII)
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3
Q

Which alcohol being oxidised creates the formation of an aldehyde?

A

Primary alcohols

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4
Q

Show me the equation of the formation of an aldehyde from the oxidisation of primary alcohols
(Whiteboard needed)

A

Where’s your whiteboard?

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5
Q

Which alcohol being oxidised creates the formation of a ketone?

A

Secondary alcohols

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6
Q

Show me the equation of the formation of a ketone from the oxidisation of secondary alcohols
(Whiteboard needed)

A

Where’s your whiteboard?

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7
Q

What are the 2 reagents used to distinguish between aldehydes and ketones

A
  • Tollen’s reagent
  • Fehling’s reagent
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8
Q

What consists of Tollen’s reagent?
(2 things + 1 what?)

A
  • Mild oxidising agents such as Ag+
  • Usually an ammoniacal solution of silver nitrate
  • contains diamminesilver(I) ion, [(NH302Ag]+)
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9
Q

What does Tollen’s reagent oxidise?

A

The aldehyde

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10
Q

What observations are there from aldehyde with Tollen’s reagent?
and how?

A
  • Silver mirror forms
  • Oxidised further
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11
Q

What does Tollen’s reagent not oxidise?

A

The ketone

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12
Q

What observations are there from ketone with Tollen’s reagent?
and how?

A
  • No observable change or goes black
  • Cannot be oxidised further
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13
Q

Equation for aldehyde with Tollen’s reagent?

A

Get your whiteboard
Carboxylic acid formed i think

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14
Q

Equation for ketone with Tollen’s reagent?

A

It don’t work

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15
Q

What is step 1 of Tollen’s reagent experiment
(Method)

A
  1. Add 1cm (depth) of silver nitrate to a boiling tube
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16
Q

What is step 2 of Tollen’s reagent experiment
(Method)
(2-way)

A
  1. Add sodium hydroxide dropwise
  2. until a brown ppt appears
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17
Q

What is step 3 of Tollen’s reagent experiment
(Method)
(2-way)

A
  1. Add ammonia (ammonium hydroxide)
  2. until the brown ppt disappears
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18
Q

What is step 4 of Tollen’s reagent experiment
(Method)
(2-way)

A
  1. Add a squirt of glucose (aldehyde substitute)
  2. to the mixture and warm in water bath
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19
Q

What consists of Fehling’s reagent?

A

2 solutions

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20
Q

What is solution A of Fehling’s reagent?

A

Aqueous copper(II) sulfate

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21
Q

What is solution B of Fehling’s reagent?

A

Sodium potassium tartrate (dissolved aq sodium hydroxide don’t listen to that part it’s wrong lol)

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22
Q

What does Fehling’s reagent oxidise?

A

The aldehyde

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23
Q

What observations are there from aldehyde with Fehling’s reagent?

A

Blue to brick-red

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24
Q

What does Fehling’s reagent not oxidise?

A

The ketone

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25
Q

What observations are there from ketone with Fehling’s reagent?

A

No observable change

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26
Q

Equation for aldehyde with Fehling’s reagent?

A

Get the whiteboard

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27
Q

Equation for ketone with Fehling’s reagent?

A

It don’t work

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28
Q

What is step 1 of Fehling’s reagent experiment
(Method)

A
  1. Place 1cm depth of solution A in a test tube
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29
Q

What is step 2 of Fehling’s reagent experiment
(Method)

A
  1. Add 1cm depth of solution B to solution A
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30
Q

What is step 3 of Fehling’s reagent experiment
(Method)

A
  1. Add a few drops of the aldehyde
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31
Q

What is step 4 of Fehling’s reagent experiment
(Method)

A
  1. Place in a warm water bath
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32
Q

What are 2 reagents used to reduce aldehydes and ketones?

A
  • Sodium borohydride (NaBH3)
  • Lithium aluminium hydride (LiAlH4)
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33
Q

What are the reaction conditions needed to reduce aldehydes and ketones

A

Dissolve in acid/water

34
Q

Eqn of reduction of aldehydes and ketones
(Whiteboard)
(Just do aldehyde insteada ketone)

A

H3C-C(=O)-H + 2[H] -> H3C-CH(OH)-H

35
Q

If u add HCN to ethanal/propanone, what’s that mechanism called?

A

Nucleophilic addition

36
Q

What is the rate and how do u increase it?… for the addition of HCN to ethanal/propanone?

A
  • Slow
  • Increases by addition of alkali/cyanide ions
37
Q

How does adding alkali for the addition of HCN to ethanal/propanone greatly increase rate?
(2-way)

A
  • Neutralises some of the HCN molecules
  • giving higher conc. of cyanide ions
38
Q

Equation of addition of HCN to ethanal/propanone?
(Whiteboard)

A

H3C-C(=O)-H + HCN/KCN -> H3C-CH(OH)-CN

39
Q

Mechanism of addition of HCN to ethanal/propanone?
(Do ethanal insteada propanone)
(Whiteboard)

A

Refer to the booklet

40
Q

How do u convert ethanenitrile to its corresponding carboxylic acid?

A

Hydrolysis

41
Q

What happens if u do acid hydrolysis towards ethanenitrile?
(2 things)

A
  • You gain an ethanoic acid
  • almost similar to normal hydrolysis
42
Q

How is acid hydrolysis performed towards ethanenitrile?
(2-way)

A
  • Nitrile heated under reflux
  • with dilute acid (e.g. dilute hydrochloric acid)
43
Q

Even if u do acid hydrolysis, how would u gain just the carboxylic/ethanoic acid?

A

Distill off the mixture

44
Q

Equation of acid hydrolysis towards ethanenitrile?
(Whiteboard)

A

H3C-C≡N -> H3C-C(=O)OH + +NH4

-> = (H+/H2O) or (HCl(aq))

45
Q

What are 2 other hydrolysis’ other than normal hydrolysis?

A
  • Acid hydrolysis
  • Alkali/Base hydrolysis
46
Q

What is acid/alkali hydrolysis used for?

A

Produce carboxylic acids

47
Q

What’s the difference with alkali/base hydrolysis?
(2 things)

A
  • It is a two-step reaction
  • Produces a salt first
48
Q

What happens if u do alkali/base hydrolysis towards ethanenitrile?
(2-way)

A
  • Gain solution containing ethanoate ions
  • and ammonia
49
Q

Equation of alkali/base hydrolysis towards ethanenitrile?

A

H3C-C≡N -> H3C-C(=O)O-Na + NH3

-> = NaOH(aq)

50
Q

What’s the 2nd step to gaining the carboxylic acid after step 1 of alkali/base hydrolysis towards ethanenitrile?
(4 things)

A
  • Liberate the “weak acid”
  • Supply enough hydrogen ions from a strong acid
  • (Hydrochloric acid)
  • Enough to the mixture = acidic
51
Q

Equation of step 2 of alkali/base hydrolysis towards ethanenitrile?

A

H3C-C(=O)O-Na+ -> H3C-C(=O)OH + Na+/Cl-?

-> = HCl(aq)

52
Q

What are 2 other ways to distinguish between aldehydes and ketones?

A
  • Reaction with 2, 4-DNP
  • Reaction with Iodoform
53
Q

Long form of 2,4-DNP?

A

2, 4-dinitrophenylhydrazine reagent

54
Q

What usually happens during the reaction with 2,4-DNP and aldehyes/ketones
(2 things)

A
  • Carbonyl group undergoes nucleophilic attack
  • Adduct loses a small molecule (usually H2O)
55
Q

What happens when the carbonyl compound reacts with the reagent “2,4-DNP”?
How’s the of carbonyl compound identified?
(2 things + 1 thing)

A
  • Results in a yellow/orange solid (corresponding hydrazone)
  • Derivatives may be isolated & purified
  • Based on the mp of the 2,4-dinitrophenylhydrazone that is formed
56
Q

How many steps are there to the method of the reaction with 2,4-DNP?

A

5 steps

57
Q

Step 1 of the reaction with 2,4-DNP w/ aldehydes/ketones
(3-way)

A
  • Add 10 drops of the aldehyde/ketone
  • to a solution of 2,4DNPH
  • in ethanol
58
Q

Step 2 of the reaction with 2,4-DNP w/ aldehydes/ketones

A

Observer the formation of an orange ppt

59
Q

Step 3 of the reaction with 2,4-DNP w/ aldehydes/ketones

A

Filter under reduced pressure

60
Q

Step 4 of the reaction with 2,4-DNP w/ aldehydes/ketones
(1 thing + 2-way)

A
  • Recrystallised from min. volume of hot ethanol
  • To obtain pure sample
  • filter under reduce pressure
61
Q

Step 5 of the reaction with 2,-DNP w/ aldehydes/ketones

A

Measure melting point of sample

62
Q

What observations are there with aldehyde and 2,4-DNP reagent?

A

Orange crystal formed

63
Q

The deduction of an aldehyde with 2,4-DNP reagent?

A

Contains a carbonyl group

64
Q

What observations are there with ketone and 2,4-DNP reagent?

A

Red-yellow crystal formed

65
Q

The deduction of a ketone with 2,4-DNP reagent?

A

Contains a carbonyl group
(hm)

66
Q

What is the reaction with 2,4-DNP an example of?

A

Nucleophilic addition then elimination mecahnism
(You don’t need to know the mechanism)

67
Q

Explain the theory of the reaction with 2,4-DNP?
(1 thing + 2-way)

A
  • 2,4-DNPH forms derivative of the aldehyde-ketone that is a solid
  • Once purified, can measure mp of solid
  • then compare result to a literature ref.
68
Q

What does it mean if the mp of the solid formed is sharp?
(Theory of the reaction with 2,4-DNP)

A

Substance is pure

69
Q

What does it mean if the sample of the solid melts over a range?
(Theory of the reaction with 2,4-DNP)

A

Probably impure

70
Q

How does the iodoform test take place?
(4 steps)

A
  • Iodine solution added to small amount of aldehyde/ketone,
  • followed by enough NaOH solution,
  • to remove the colour of iodine
  • If nothing happens, warm the mixture gently
71
Q

What is the positive result with the iodoform test?

A
  • Very pale yellow precipitate of iodoform (CHI3)
72
Q

How else can a positive result with the iodoform test be recognised?
(2 things)

A
  • Faintly “medical” smell
  • Used as an antiseptic on sticky plasters
73
Q

How many steps are there to the method of the iodoform test?

A

6 steps

74
Q

State step 1 of the iodoform test

A
  1. Add 1 cm3 of propanone to a conical flask
75
Q

State step 2 of the iodoform test
(2-way)

A
  1. To 12 cm3 of deionised water
  2. add 5g of potassium iodide (KI)
76
Q

State step 3 of the iodoform test

A
  1. Add 5 cm3 of “M sodium hydroxide
77
Q

State step 4 of the iodoform test
(2-way)

A
  1. Add 20 cm3 of sodium chlorate(I) solution (sodium hypochlorite)
  2. slowly from separating/dropping funnel
78
Q

State step 5 and 6 of the iodoform test

A
  1. Swirl to mix
  2. Observe any changes
79
Q

What’s the theory with the iodoform test?
(2-way + 1 thing)

A
  • Iodine reacts with methyl carbon
  • to form CHI3 that leaves the molecule
  • Iodorm gives a characteristic hospital smell
80
Q

Another word for iodoform
(we aren’t meant to like this one)

A

Triiodomethane

81
Q

What other positive test can u get with the iodoform test?
(3-way)

A
  • Ethanol (only primary alcohol),
  • & secondary alcohols,
  • where OH group next to methyl group
82
Q

Little tweaks perhaps, then u can spam ppq

A

HOWEVER, chem tests always intertwine with other topics. Therefore, U should, definitely, clarify on 4.2 probably? Or some of them, it’s knowing the tests that appears to be very important ¬.¬

A Chem Finale pt 1. (10 decks)

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