Chapter 26 - Carbonyls Flashcards

1
Q

How to remember than an aldehyde has a C=O at the end of the carbon chain?

A

aldehyDe enD

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2
Q

Why is a colour change from orange to green observed?

A

change in oxidation state of the chromium gives the colour change

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3
Q

the importance of adding CN to a carbonyl compound?

A
  • inc no. of Cs in a molecule

- hydroxynitriles (product formed) are used in industrial processes

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4
Q

all carbonyl compounds contain a ?

A

C=O

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5
Q

Why do we use Brady’s reagent and recrystallise (ect) instead of just measuring the BP of the aldehyde/ ketone ?

A

BPs can be very similar, melting points of the precipitates have a much larger diff so easier to distinguish using this

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6
Q

the proper name for Tollens’ reagent is?

A

ammonical silver nitrate

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7
Q

How do we make Tollens reagent?

A
  • add silver nitrate solution to a test tube
  • add a few drops of NaOH, a pale brown precipitate forms
  • add dilute ammonia drop-wise until the precipitate dissolves
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8
Q

after making Tollen’s reagent?

A
  • add ketone/ aldehyde to the test tube
  • place the test tube in a water bath
  • DON’T USE A BUNSEN AS ALDEHYDES AND KETONES ARE FLAMMABLE
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9
Q

how to get rid of anti-bumping granules?

A

hot filtration

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10
Q

how are liquids always seperated?

A

distillation

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11
Q

how to determine purity of a substance?

A
  • IR
  • MS
  • Measure BP, compare to data book
  • pure substances melt over a narrow range of temps
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12
Q

aldehyde vs ketone?

A

H attached to C=O makes it an aldehyde

Ketones hv carbonyl bond in middle (made from secondary acl)

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13
Q

ketone ending?

A

-one

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14
Q

aldehyde ending?

A

-al

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15
Q

what happens when propanal is added to water?

A
  • no mixing

- extra CH2 means molecule has greater SA so more induced dipole forces

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16
Q

what happens when propanone is added to water?

A

mixes

  • dipole means H bonds can form w water
  • less induced dipole forces than in propanal so easier to overcome
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17
Q

what happens when propanal is added to Na2Cr2O7 ?

A
  • Oxidation: propanal + [O] ➡ propanoic acid
  • orange ➡ green colour change
  • Reduction: 14H+ + Cr2O7 2- + 6e- ➡ 2Cr3+ (green)+ 7H2O
18
Q

what happens when propanone is added to Na2Cr2O7?

A

stays orange no oxidation occurs

19
Q

what is Tollen’s reagent?

A

Oxidising agent

20
Q

What happens when propanal is added to Tollens?

A
  • Ox: propanal + [O] ➡ propanoic acid

- Red: Ag++ e- ➡ Ag (silver mirror)

21
Q

what happens when propanone is added to tollens

A
  • clear: precipitate dissolves in ammonia

- doesn’t oxidise; no silver mirror

22
Q

what is Brady’s reagent also known as?

23
Q

What does brady’s reagent do?

A

detects C=O

+ result is orange crystals

24
Q

how to work out which aldehyde/ ketone from Brady’s + result?

A
  • distil orange crystals
  • measure BP
  • compare to values in databook to identify
25
nucleophile definition?
a species w a lone pair of electrons that can be donated to form a dative covalent bond
26
in organic chemistry?
- Ox: addition of O2 | - Reduction: addition of H
27
reduction of carbonyl compounds is?
- the opposite of oxidation | - primary/ secondary alcohols are produced
28
for carbonyl compounds to be reduced there must be ?
- powerful reducing agent - NaBH4 (aq) | - HAS TO BE IN WATER
29
Ketone to 2° alcohol equation?
ketone + 2[H] ➡ 2° alcohol
30
aldehyde to 1° alcohol equation?
aldehyde + 2[H] ➡ 1° alcohol
31
reduction of carbonyl compounds is?
nucleophilic addition (double bond remember)
32
reduction of CCs NA mechanism number of steps and arrows?
3 steps, 4 curly arrows (check for arrow on C=O)
33
Where do the hydride ions come from for the reduction of CCs?
BH4-
34
reaction of CCs w HCN?
- NOT A REDUCTION - CN & H added not just H | - either KCN/ HCN and H2SO4 are the reagents
35
what is the problem w HCN?
- toxic - low BP - vaporises- dangerous - so we make it
36
why do we react CCS w HCN?
It can be used to ⬆ the no. of Cs in an organic molecule which is useful for organic synthesis
37
what is produced by the reaction of CCs w HCN?
hydroxynitriles
38
hydrogen cyanide creation?
- happens in situ - H2SO4 + NaCN ➡NaHSO4 + HCN (weak acid) HCN reversible ➡H+ CN- nucleophile (has lone pair on C)
39
⭐ be careful when naming hydroxynitriles?
the C of the CN becomes C1
40
HCN + CC ➡ hydroxynitrile: number of steps/ arrows in mechanism?
- 3 curly arrows | - 2 steps
41
when writing mechanism of HCN + CC ⭐
remember to start w formation/ dissociation of HCN
42
the carbonyl bond is made up of?
1 sigma, 1 Pi bond | p orbitals overlap sideways to form the Pi bond