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Chemistry > 3.5 Alcohols > Flashcards

3.5 Alcohols Flashcards

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1
Q

Draw the displayed formula for butan-2-ol

A

(see page 1 in the chemrevise revision guide)

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2
Q

Draw the displayed formula for 2-hydroxypropanoic acid

A

(see page 1 in the chemrevise revision guide)

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3
Q

Draw the displayed formula for ethane-1,2-diol

A

(see page 1 in the chemrevise revision guide)

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4
Q

Draw the displayed formula for propane-1,2,3-triol

A

(see page 1 in the chemrevise revision guide)

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5
Q

In alcohols what are the bond angles for the:
H-C-H
C-C-O

A

109.5ºC (tetrahedral shape), because there are 4 bond pairs of electrons repelling to a position of minimum repulsion.

(see page 1 in the chemrevise revision guide)

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6
Q

In alcohols what is the bond angle for the:

H-O-C

A

104.5ºC (bent line shape), because there are 2 bond pairs of electrons and 2 lone pairs repelling to a position of minimum repulsion. Lone pairs repel more than bond pairs so the bond angle is reduced.

(see page 1 in the chemrevise revision guide)

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7
Q

Why do alcohols have relatively low volatility and high boiling points?

A

Alcohols have relatively low volatility and high boiling points due to their ability to form hydrogen bonds between alcohol molecules.

(see page 1 in the chemrevise revision guide)

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8
Q

Draw and name an example of a primary alcohol, describe what one is.

A

Primary alcohols are alcohols where 1 carbon is attached to the carbon adjoining the oxygen.

(see page 1 in the chemrevise revision guide)

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9
Q

Draw and name an example of a secondary alcohol, describe what one is.

A

Secondary alcohols are alcohols where 2 carbons are attached to the carbon adjoining the oxygen.

(see page 1 in the chemrevise revision guide)

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10
Q

Draw and name an example of a tertiary alcohol, describe what one is.

A

Tertiary alcohols are alcohols where 3 carbons are attached to the carbon adjoining the oxygen.

(see page 1 in the chemrevise revision guide)

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11
Q

What is the general formula for alcohols?

A

CnH2n+1OH

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12
Q

What is an oxidising agent that you can use to oxidise alcohols?

A

Potassium dichromate, K2Cr2O7 is an oxidising agent that causes alcohols to oxidise.

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13
Q

When partially oxidising a primary alcohol what is the functional group change?

A

primary alcohol -> aldehyde

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14
Q

When partially oxidising a primary alcohol what are the reagents and conditions of this reaction?

A

(see page 2 in the chemrevise revision guide)

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15
Q

Draw the displayed formula of ethanal

A

(see page 2 in the chemrevise revision guide)

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16
Q

Draw the equation for the partial oxidation of propane-1-ol.

A

(see page 2 in the chemrevise revision guide)

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17
Q

Draw the apparatus for a lab distillation.

A

(see page 2 in the chemrevise revision guide)

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18
Q

When fully oxidising a primary alcohol what is the functional group change?

A

primary alcohol -> carboxylic acid

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19
Q

When fully oxidising a primary alcohol what are the reagents and conditions of this reaction?

A

(see page 3 in the chemrevise revision guide)

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20
Q

Draw the displayed formula for propanoic acid.

A

(see page 3 in the chemrevise revision guide)

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21
Q

Draw the equation for the full oxidation of propane-1-ol.

A

(see page 3 in the chemrevise revision guide)

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22
Q

Draw the apparatus for a lab reflux.

A

(see page 3 in the chemrevise revision guide)

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23
Q

What is a distillation used for?

A

In general it is used as a separation technique to separate an organic product from its reacting mixture. In order to maximise yield collected, only collect the distillate at the approximate boiling point of the desired aldehyde and not higher.

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24
Q

In a distillation why does the water go in the bottom of the condenser to go against gravity?

A

It allows more efficient cooling and prevents back flow of water.

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25
Q

Why are electric heaters often used in a distillation?

A

Because organic chemicals are normally highly flammable and could set on fire with a naked flame.

26
Q

When is reflux used?

A

Reflux is used when heating organic mixtures for long periods. The condenser prevents organic vapours from escaping by condensing them back to liquids.

27
Q

Why do you never seal the end of the condenser in a reflux apparatus? (or a distillation set up)

A

The build up go gas pressure could cause the apparatus to explode. This is true of any apparatus where volatile liquids are heated including the distillation set up.

28
Q

Why are anti-bumping granules added to both distillation and reflux?

A

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

29
Q

When oxidising a secondary alcohol what is the functional group change?

A

secondary alcohol -> ketone

30
Q

When oxidising a secondary alcohol what are the reagents and conditions of this reaction?

A

(see page 4 in the chemrevise revision guide)

31
Q

Draw the equation for the oxidation of propan-2-ol.

A

(see page 4 in the chemrevise revision guide)

32
Q

Why can tertiary alcohols not be oxidised by potassium dichromate?

A

Because there is no hydrogen atom bonded to the carbon with the -OH group.

33
Q

How do you distinguish between Aldehydes and Ketones in the lab? Then test for the presence of a carboxylic acid?

A
  • Tollen’s reagent
  • Fehling’s solution

The presence of a carboxylic acid can be tested by addition of sodium carbonate. It will fizz and produce carbon dioxide.

34
Q

Describe the Tollen’s reagent experiment.

A

(see page 4 in the chemrevise revision guide)

35
Q

Describe the Fehling’s solution experiment.

A

(see page 4 in the chemrevise revision guide)

36
Q

When reacting alcohols with dehydrating agents what is the functional group change?

A

alcohol -> alkene

37
Q

When dehydrating an alcohol what are the:

  • reagents
  • conditions
  • role of reagent
  • type of reaction
A

(see page 5 in the chemrevise revision guide)

38
Q

Draw the equation for reacting propan-1-ol with dehydrating agents

A

(see page 5 in the chemrevise revision guide)

39
Q

Draw the mechanism for reacting propan-1-ol with dehydrating agents

A

(see page 5 in the chemrevise revision guide)

40
Q

What two products would form when reacting butan-2-ol with a dehydrating agent?

A
  • but-1-ene
  • but-2-ene

(see page 5 in the chemrevise revision guide)

41
Q

What are 2 examples of a dehydrating agent?

A

H2SO4

H3PO4

42
Q

Describe using words a dehydration reaction.

A

A dehydration reaction is the removal of a water molecule from a molecule.

43
Q

What are the two methods of producing ethanol?

A
  • Fermentation

- Industrial formation from ethene

44
Q

Give the word equation for fermentation.

A

glucose -> ethanol + carbon dioxide

45
Q

Give the equation for fermentation.

A

C6H12O6 -> 2CH3CH2OH + 2CO2

46
Q

What are the 3 conditions needed for fermentation?

A
  • Yeast
  • No air
  • Temperatures 30 - 40ºC (optimum temp around 38ºC)
47
Q

What happens to the fermentation reaction when the temperature is too low?

A

The reaction is too slow.

48
Q

What happens to the fermentation reaction when the temperature is too high?

A

The yeast dies and the enzymes denature.

49
Q

Why is fermentation done in an absence of air?

A

Fermentation is done in an absence of air because the presence of air can cause extra reactions to occur. It oxidises the ethanol produced to ethnic acid (vinegar).

50
Q

What are the 2 advantages and 3 disadvantages of fermentation?

A

(see page 6 in the chemrevise revision guide)

51
Q

What is the reagent in the industrial formation of ethanol from ethene?

A

Ethene - from the cracking of fractions from distilled crude oil.

52
Q

Give the equation for the industrial formation of ethanol from ethene.

A

CH2=CH2(g) + H2O(g) - > CH3CH2OH(l)

53
Q

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

A

Hydration/addition

54
Q

Describe in words a hydration reaction.

A

Hydration is the addition of water to a molecule.

55
Q

What are the 3 essential conditions for the industrial formation of ethanol from ethene?

A
  • High temperature 300ºC
  • High pressure 70 atm
  • Strong acidic catalyst of conc H3PO4
56
Q

What are the 3 advantages and the 3 disadvantages of the industrial formation of ethanol from ethene?

A

(see page 6 in the chemrevise revision guide)

57
Q

Draw the mechanism for the industrial formation of ethanol from ethene.

A

(see page 6 in the chemrevise revision guide)

58
Q

What is a biofuel?

A

A biofuel is a fuel produced from plants.

59
Q

What does the term carbon neutral mean?

A

Th term carbon neutral refers to “an activity that has no net annual carbon (greenhouse gas) emissions to the atmosphere”.

60
Q

Ethanol produced from fermentation is a biofuel. Why can it be argued that ethanol produced from this method is classes as carbon neutral?
Use equations to support your answer.

What does this argument not take into account?

A

Any carbon dioxide given off when the biofuel is burnt would have been extracted from the air by photosynthesis when the plant grew. There would be no net CO2 emission into the atmosphere.

(see page 7 in the chemrevise revision guide for equations)

This does not take into account any energy needed to irrigate plants, fractionally distil the ethanol from the reaction mixture or process the fuel. If the energy for these processes comes from fossil fuels then the ethanol produced is not carbon neutral.

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