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N Chemistry A Level > Topic 17 Organic II > Flashcards

Topic 17 Organic II Flashcards

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1
Q

What are 2 types of isomerism?

A

structural
stereo

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2
Q

what are 3 types of structural isomerism?

A
  • chain
  • position
  • functional group
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3
Q

what are 2 types of stereoisomerism?

A
  • geometric
  • optical
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4
Q

What are optical isomers?

A
  • same molecular
  • same structural
  • different 3D spatial arrangement
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5
Q

what are conditions needed for geometric isomers?

A

double C=C bonds as it limits rotations

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6
Q

What are conditions needed for optical isomers?

A
  • must have chiral centre
    (usually C)
  • Has 4 (or more) groups bonded to it
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7
Q

What does nonsuperimposable mean?

A

Like hands
have the same properties and structure
but are mirror images of each other

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8
Q

What can make a racemic mixture?

A
  • SN1 (sometimes)
  • MUST have chiral centre
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9
Q

No rotation when plane polarised light is shown through…

A

think RACEMIC MIXTURE
For sure

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10
Q

what is the only difference between enantiomers?

A

rotate plane polarised (monochromatic) light in equal but opposite directions

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11
Q

why do enantiomers rotate monochromatic lights in different directions?

A

due to their different arrangements of atoms in space

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12
Q

why must it be racemic mixtures when there are no rotations through polarised light?

A

enantiomer rotations cancel out

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13
Q

How are enantiomers / racemic formed?

A

50/50 chance for SN1 attack of chiral centre (from above or below trigonal planar plane)
other bonds pushed up or down when new bond formed
forming enantiomers in equal portions

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14
Q

What can be used to test for carbonyls?

A
  • dichromate
  • Benedict’s/fehlings
  • tollens (ammoniacle silver nitrate)
  • Lithium aluminium hydride (LiAlH4)
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15
Q

What is dichromate’s reaction to carbonyls? +why?

A

Aldehyde: Orange to green as aldehyde is oxidised to -COOH
Ketone: remain orange, no change

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16
Q

Can ketones be oxidised or reduced?

A

Only reduced
By LiAlH4

17
Q

What is the Benedict’s/Fehling’s reactions to carbonyls?

A

Aldehydes: Blue to brick red as they get oxidised
Cu 2+ + Aldehyde -> Cu3+
No change in ketones

18
Q

Aldehyde + alkaline oxidising agent ->

A

Carboxylate + water

19
Q

How to turn carboxylate into carboxylic acid?

A

Add strong acid
To Protonate into carboxylic acid

20
Q

What is tollens reagent’s reaction to carbonyls?

A

Aldehydes: Silver mirror formed - Ag (s) from Ag+
No change in ketone

21
Q

What is LiAlH4?

A

Lithium aluminium hydride

22
Q

What is LiAlH4’s reactions to carbonyls?

A

In dry ether
Acts as reducing agent - [H]
Aldehyde + [H] → 1° alcohol
Ketone + 2[H] → 2° alcohol

23
Q

What is the the reaction equation of Fehling’s solution with aldehyde? And explain colour change

A

2 Cu2+ (aq) + 2OH- (aq) + 2e- -> Cu2O (s) + H2O (l)
Hence blue -> red

24
Q

What is tollen’s reagent with aldehyde? And what change is observed?

A

2Ag+ (aq) + 2OH- (aq) -> Ag2O (s) + H2O (l)

25
Q

Why can’t tertiary alcohols or ketones be oxidised?

A

They must have an H atom bonded to C to be oxidised

26
Q

What is [H]?

A

Reducing agent

27
Q

What is formed when carbonyls + HCN?

A

hydroxy nitrile

28
Q

What does HCN stand for and is it a strong or weak acid?

A

Hydrogen cyanide
Weak

29
Q

What catalyst can be added to the carbonyl + HCN reaction to speed up RoR?

A

KCN (salt)
It provides loads of cyanide nucleophiles
(In this case conc of catalyst impacts RoR)

30
Q

Are carboxylic acids strong or weak acid?

A

Weak

31
Q

How to test for carboxylic acids?

A

Add sodium carbonate (Na2CO3 / NaHCO3)
- fizzing to indicate CO2 produced

32
Q

What’s the best indicator to use to test for carboxylic acids?

A

Universal indicator
Or pH probe

33
Q

How soluble is carboxylic acids in water? Why?

A
  • very!
  • when R group is small, H bonds can form
34
Q

Does solubility for carboxylic acids increase or decrease as chain length increases? Why?

A

Carb. aciDDDDs so DDDDecreases
As non polar part of molecule is more significant

35
Q

What’s a dimer in terms of carboxylic acids

A

2 of them bonded together covalently
Therefore explains high mp/bp

36
Q

What are 3 methods to make carboxylic acids?

A
  1. Distill 1° alcohol with [O] like K2Cr2O7
  2. Reflux 2° alcohol with [O]
  3. Hydrolysis of nitriles
37
Q

What are 2 methods of hydrolysis of nitriles to make carboxylic acids?

A
  1. Acid catalysed
  2. Alkali catalysed, makes cadboxyLATE then protonate by adding strong acid
38
Q

How to make carboxylic acids via hydrolysis using acids?

A

nitrile + water -H+—> carboxylic acid + ammonia

39
Q

How to make carboxylic acids using nitriles and alkali?

A

Nitrile + water + OH- —> carboxyLATE + ammonia
Then protonate by adding STRONG acid to make

N Chemistry A Level (19 decks)

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