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AQA: Chemistry Paper 2 > Alcohols > Flashcards

Alcohols Flashcards

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1
Q

What is the general formula of an alcohol?

A

CₙH₂ₙ₊₁OH

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2
Q

Volatility of alcohols:

A

low

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3
Q

Boiling points of alcohols:

A

high

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4
Q

Why do alcohols have high boiling points?

A

high boiling points due to their ability to form

hydrogen bond between alcohol molecules

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5
Q

What are the different types of alcohols?

[3]:

A
  • Primary alcohols
  • Secondary alcohols
  • Tertiary alcohols
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6
Q

What makes a secondary alcohol?

A

Secondary alcohols are alcohols where 2 carbon are attached to the carbon with the functional group

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7
Q

What happens when you oxidise a primary alcohol?

A

An aldehyde is formed

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8
Q

Partial oxidation of primary alcohols:

A

primary alcohol → aldehyde

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9
Q

What are the reagents in the partial oxidation of primary alcohols?
[2]:

A
  • potassium dichromate (VI) solution

- dilute sulfuric acid

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10
Q

What are the conditions in the partial oxidation of primary alcohols? [3]:

A
  • Limited amount of potassium dichromate (VI)
  • Warm gently
  • Distil out the aldehyde
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11
Q

What does the dichromate ion look like?

A

Cᵣ₂O₇²⁻

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12
Q

What would you observe when dichromate ions are reduced? [2]:

A
  • Orange → Green

- Cᵣ₂O₇²⁻ reduced to Cr³⁺

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13
Q

What do you do when writing the formula of aldehydes in a condensed way?

A

write CHO and not COH

e.g.CH₃CH₂CHO

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14
Q

Distillation equipment [5]:

A
  • Thermometer
  • Bung
  • Heat
  • Leibig condenser
  • Collection flask
  • Anti bumping granules
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15
Q

Where should the thermometer be during distillation and why?

A
  • At the T junction connecting to the condenser

- To measure the correct boiling point

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16
Q

Why are electric heaters often used to heat organic chemicals?

A

Organic chemicals are normally highly flammable and could set on fire with a naked flame

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17
Q

Full Oxidation of Primary Alcohols:

A

primary alcohol → carboxylic acid

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18
Q

What are the reagents for the full oxidation of primary alcohols? [2]:

A
  • potassium dichromate(VI) solution

- dilute sulfuric acid

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19
Q

What are the conditions for the full oxidation of primary alcohols? [3]:

A
  • an excess of dichromate
  • heat
  • under reflux
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20
Q

What is reflux used for? [2]:

A
  • Reflux is used when heating organic reaction mixtures for long periods
  • The condenser prevents organic vapours from escaping
    by condensing them back to liquids
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21
Q

Why do you never seal the end of the condenser during reflux?

A

build up of gas pressure could cause the apparatus to explode

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22
Q

Why are anti bumping granules added to the flask during distillation and reflux?

A

To prevent vigorous, uneven boiling by making small bubbles form instead of large bubbles

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23
Q

Reflux equipment [4]:

A
  • Anti-bumping granules
  • Round-bottomed flask
  • Heat
  • Condenser
24
Q

Oxidation of secondary alcohols:

A

secondary alcohol → ketone

25
Q

What are the reagents for the oxidation of secondary alcohols? [2]:

A
  • potassium dichromate(VI) solution

- dilute sulfuric acid

26
Q

What are the conditions for the oxidation of secondary alcohols?

A

heat under reflux

27
Q

Observation for the oxidation of secondary alcohols?

A

the orange dichromate ion Cᵣ₂O₇²⁻ reduces to the green Cr³⁺+ ion

28
Q

Why can tertiary alcohols not be oxidised by potassium dichromate?

A

There is no hydrogen

atom bonded to the carbon with the -OH group

29
Q

What is the difference between aldehydes and ketones?

A

Aldehydes can be further oxidised to carboxylic acids whereas ketones cannot be further oxidised

30
Q

What tests are used to distinguish between aldehydes and ketones? [2]:

A
  • Tollens’ Reagent

- Fehling’s solution

31
Q

How is Tollens’ reagent formed?

[2]:

A
  • By mixing aqueous ammonia and silver nitrate.

- Forms the ion [Ag(NH₃)₂]⁺

32
Q

What are the conditions for Tollens’ reagent?

A

Heat gently

33
Q

Tollens’ reagent observation

[2]:

A
  • Aldehydes = silver mirror

- Ketones = no visible change

34
Q

What does Fehling’s solution contain?

A

Blue Cu²⁺ ions

35
Q

What are the conditions for Fehling’s solution?

A

Heat gently

36
Q

Fehling’s solution observations

[2]:

A
  • Aldehydes = Blue Cu 2+ ions in
    solution change to a red precipitate of Cu₂O
  • Ketones = no visible reaction
37
Q

How else can a carboxylic acid be tested for?

[2]:

A
  • Tested by addition of sodium carbonate

- It will fizz and produce carbon dioxide

38
Q

Reaction of Alcohols with Dehydrating Agents:

A

Alcohol → Alkene

39
Q

Reagents for the reaction of alcohols with dehydrating agents? [2]:

A

Concentrated sulfuric or phosphoric acids

40
Q

What are the conditions for the reaction of alcohols with dehydrating agents?

A

Warm under reflux

41
Q

What is the mechanism for the reaction of alcohols with dehydrating agents?

A

elimination

42
Q

What does producing alkenes from alcohol provide?

A

provides a possible route to polymers without using monomers derived from oil

43
Q

What are the methods for the formation of ethanol?

[2]:

A
  • Fermentation

- Industrial formation from ethene

44
Q

What are the conditions for fermentation? [3]:

A
  • Yeast
  • No air/ anaerobic
  • Temperatures 30-40ᵒC
45
Q

What is the optimum temperature for fermentation and why? [3]:

A
  • Around 38ᵒC
  • At lower temperatures the reaction is too slow.
  • At higher temperatures the yeast dies and the enzymes
    denature
46
Q

Why is fermentation done in the absence of air?

[2]:

A
  • The presence of air can cause extra reactions to occur.
  • It oxidises the ethanol produced to ethanoic acid
    (vinegar)
47
Q

Advantages of fermentation [2]:

A
  • Sugar is a renewable resource
  • Production uses low-level technology / cheap
    equipment
48
Q

Disadvantages of fermentation [3]:

A
  • Batch process is slow and gives high production
    costs
  • Ethanol made is not pure and needs purifying by
    fractional distillation
  • Depletes land used for growing food crops
49
Q

What type of reaction is the industrial formation of ethanol from ethene?

A

Hydration/ addition

50
Q

Conditions for the industrial formation of ethanol from ethene
[3]:

A
  • high temperature 300 °C
  • high pressure 70 atm
  • strong acidic catalyst of conc H₃PO₄
51
Q

What are the advantages of the industrial formation of ethanol from ethene?
[3]:

A
  • faster reaction
  • purer product
  • continuous process (which means cheaper manpower)
52
Q

What are the disadvantages of the industrial formation of ethanol from ethene?
[3]:

A
  • high technology equipment needed (expensive
    initial costs)
  • ethene is non-renewable resource (will become
    more expensive when raw materials run out)
  • high energy costs for pumping to produce high
    pressures
53
Q

What is ethanol?

A

A biofuel produced from plants

54
Q

What is the ethanol produced from fermentation?

A

A biofuel

55
Q

What does carbon neutral mean?

A

an activity that has no net annual carbon (greenhouse gas) emissions to the atmosphere

AQA: Chemistry Paper 2 (7 decks)

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