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Organic Chemistry > 3.3.5 - alcohols > Flashcards

3.3.5 - alcohols Flashcards

1
Q

what is the general formula for the alcohol homologous series

A

Cn, H2n+1, OH

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2
Q

what is the suffix for alcohols

A

-ol

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3
Q

do you need numbers for naming alcohols

A

yes - which carbon atom the alcohol functional group is attached to

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4
Q

what is the suffix for 2 -OH groups

A

-diol

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5
Q

what is the suffix for 3 -OH groups

A

-triol

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6
Q

primary alcohols

A
  • OH group is attached to a carbon with one alkyl group attached
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7
Q

secondary alcohols

A
  • Oh group is attached to a carbon with 2 alkyl groups attached
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8
Q

tertiary alcohols

A
  • Oh group is attached to a carbon with 3 alkyl groups attached
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9
Q

dehydration of alcohols

A

you can make alkenes by eliminating water from alcohols in a dehydration reaction (i.e. elimination of water)

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10
Q

what does dehydration of alcohols allow you to produce and why is this important

A

allows you to produce alkenes from renewable resources which is important as you can produces polymers e.g. polyethene without needing oil

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11
Q

in the dehydration of ethanol, what is ethanol heated with

A

ethanol is heated with a concentrated sulfuric acid catalyst

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12
Q

dehydration of an alcohol:
step 1

A
  1. lone pair of electrons from the oxygen bonds to an H+ from the acid. The alcohol is protonated, giving the oxygen a positive charge
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13
Q

dehydration of an alcohol:
step 2

A
  1. positively charged oxygen pulls electrons away from the carbon. An H20 molecule leaves, creating an unstable carbocation intermediate
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14
Q

dehydration of an alcohol:
step 3

A
  1. carbocation loses an H+
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15
Q

dehydration of an alcohol:
step 4

A
  1. alkene is formed along with H2O and H+
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16
Q

what can also be used as a catalyst in the dehydration of alcohols

A

phosphoric acid

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17
Q

give 2 ways ethanol can be produced?

A
  • hydration of ethene
  • fermentation of glucose
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18
Q

what is the standard industrial method for producing alcohols

A

hydrate an alkene using steam in the presence of an acid catalyst

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19
Q

how to produce ethanol from ethene

A

steam hydration of ethene is used industrially to produce ethanol

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20
Q

conditions for hydration of ethene to make ethanol

A

ethene can be hydrated by steam at 300 degrees C and a pressure of 60atm. it needs a solid phosphoric(V) acid catalyst

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21
Q

is the reaction to make ethanol from ethene reversible?

A

yes it is reversible

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22
Q

hydration of ethene:
step 1

A
  1. pair of electrons from the double bond bonds to an H+ from the acid
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23
Q

hydration of ethene:
step 2

A
  1. lone pair of electrons from a water molecule bonds to the carbocation
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24
Q

hydration of ethene:
step 3

A

water loses an H+

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25
Q

hydration of ethene:
step 4

A

alcohol is formed and a H+

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26
Q

how is most industrial ethanol produced?

A

by steam hydration of ethene with a phosphoric acid catalyst

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27
Q

where does the ethene for the industrial production of ethanol come from?

A

ethene comes from cracking heavy fractions of crude oil

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28
Q

why will producing ethene from fermentation become important?

A

crude oil supplies will start reducing so petrochemicals like ethene will be expensive

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29
Q

is fermentation an exothermic or endothermic reaction

A

fermentation is an exothermic reaction, carried out by yeast in anaerobic conditions (without oxygen)

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30
Q

fermentation of glucose:
step 1

A

yeast produces enzymes which convert glucose (C6, H12, O6) into ethanol and CO2

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31
Q

fermentation of glucose:
step 2

A

enzyme works best at optimum temperature of 30-4- degrees C

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32
Q

fermentation of glucose:
step 3

A

if it’s too cold, the reaction is too slow. if it’s too hot, the enzyme is denatured

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33
Q

fermentation of glucose:
step 4

A

when the solution reaches around 15% ethanol, the yeast dies. Fractional distillation is used to increase the concentration of the ethanol

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34
Q

is fermentation low tech?

A

fermentation is low tech, uses cheap equipment/renewable resources

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35
Q

fractional distillation: time/money

A

fractional distillation step needed to purify the ethanol produced using this method takes extra time and money

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36
Q

hydration of ethene:
rate of reaction

A

rate of reaction is very fast

37
Q

hydration of ethene:
quality of product

38
Q

hydration of ethene:
raw material

A

ethene from oil - a finite resource

39
Q

hydration of ethene:
process/costs

A

continuous process, so expensive equipment needed but low labour costs

40
Q

fermentation:
rate of reaction

A

rate of reaction is very slow

41
Q

fermentation:
quality of product

A

very impure - needs further processing

42
Q

fermentation:
raw material

A

sugars - a renewable resource

43
Q

fermentation:
process/costs

A

batch process, so cheap equipment needed, but high labour costs

44
Q

phosphoric acid

45
Q

sulfuric acid

46
Q

what is a biofuel

A

biofuel is a fuel made from biological material that’s recently died

47
Q

biofuel example

A

bioethanol
sugars from sugar cane can be fermented to produce ethanol, which can be added to petrol. ethanol produced in this way is a biofuel

48
Q

advantages of biofuels
sustainability

A

biofuels are renewable energy sources so are more sustainable

49
Q

advantages of biofuels
carbon neutral???

A

biofuels produce CO2 when burnt but the same amount the crop plant took in when it was growing so most biofuels are considered to be carbon neutral

50
Q

disadvantages of biofuels
food vs fuel debate

A

land used to grow crops for fuel can’t be used to grow food, may not be able to grow enough food

51
Q

disadvantages of biofuels
trees

A

trees may be cut down to create space to grow crops for biofuels = destroys habitats/carbon sinks.
trees cut down are often burnt = produces CO2

52
Q

disadvantages of biofuels
fertilisers

A

fertilisers often added to soil to increase biofuel crop production = can pollute waterways, some fertilisers release nitrous oxide (greenhouse gas)

53
Q

disadvantages of biofuels
practicality

A

most current car engines wouldn’t be able to run on fuels with high ethanol concentrations without being modified

54
Q

is ethanol a carbon neutral fuel?
photosynthesis equation

A

6C,O2 + 6H2,O = C6,H12,O6 + 6O2

55
Q

is ethanol a carbon neutral fuel?
glucose converted into ethanol equation

A

C6,H12,O6 = 2C5,H5,O,H + 2C,O2

56
Q

is ethanol a carbon neutral fuel?
combustion of ethanol equation

A

2C5,H5,O,H +6O2 = 4C,O2 + 6H2,O

57
Q

is ethanol a carbon neutral fuel?
amount of carbon dioxide taken in and given out

A

from the equations it is shown 6 moles of carbon dioxide are taken in and 6 moles of carbon dioxide are given out which implies it to be carbon neutral

58
Q

is ethanol a carbon neutral fuel?
why is it not carbon neutral

A
  • refining/transporting gives out CO2
59
Q

what does oxidising an alcohol create?

A

a carbon-oxygen double bond

60
Q

what is the simplest way to oxidise alcohols

A

by burning them

61
Q

what can you use to mildly oxide primary and secondary alcohols

A

you can used the oxidising agent acidified potassium dichromate (VI) -Kr2, Cr2, O7 to mildly oxidise primary and secondary alcohols

62
Q

what happens in the reaction using potassium dichromate (VI) as an oxidising agent

A

in the reaction the orange dichromate (VI) ion Cr2, O7 2- is reduced to the green chromium (III) ion, Cr 3+

63
Q

what are primary alcohols oxidised to

A

primary alcohols are oxidised to aldehydes then to carboxylic acids

64
Q

what are secondary alcohols oxidised to

A

secondary alcohols are oxidised to ketones only

65
Q

what are tertiary alcohols oxidised to

A

tertiary alcohols aren’t oxidised

66
Q

what compounds are aldehydes and ketones

A

aldehydes and ketones are carbonyl compounds, have the functional group C=O

67
Q

in aldehydes what is attached to the carbonyl carbon atom

A

aldehydes have a hydrogen and 1 alkyl group attached to the carbonyl carbon atom

68
Q

what is the suffix for aldehydes

69
Q

do you need numbers for naming aldehydes

A

no as the functional group is always on carbon 1

70
Q

in ketones what is attached to the carbonyl carbon atom

A

ketones have 2 alkyl groups attached to the carbonyl carbon atom

71
Q

what is the suffix for ketones

72
Q

do you need numbers for naming ketones

A

yes for ketones with 5 or more carbon

73
Q

carboxylic acid functional group

74
Q

what is the suffix for carboxylic acids

75
Q

what notation represents an oxidising agent

76
Q

colour change when acidified potassium dichromate (VI) oxidises an alcohol

A

acidified potassium dichromate (VI) ion turns from orange to green when it oxidises an alcohol

77
Q

can you control how far an alcohol is oxidised and how

A

can control how far the alcohol is oxidised by controlling the reaction conditions

78
Q

how can you just get the aldehyde when oxidising a primary alcohol

A

to get just the aldehyde you need to get it out of the oxidising solution as soon as it forms

79
Q

how do you get the aldehyde out of the oxidising solution as soon as it forms so you just get the aldehyde when oxidising a primary alcohol

A

gently heating excess alcohol with a controlled amount of oxidising agent in distillation apparatus . the aldehyde (boils at lower temp than alcohol) is distilled off immediately

80
Q

when oxidising primary alcohols to carboxylic acids what has to be done to the alcohol

A

to produce the carboxylic acid, the alcohol has to be vigorously oxidised

81
Q

oxidising primary alcohols to carboxylic acids
stage 1

A
  1. alcohol is mixed with excess oxidising agent and heated under reflux
82
Q

oxidising primary alcohols to carboxylic acids
stage 2

A
  1. heating under reflux means you can increase the temperature of ab organic reaction to boiling without losing volatile solvents, reactants or products
83
Q

oxidising primary alcohols to carboxylic acids
stage 3

A
  1. any vapourised compounds are cooled, condense and drip back into the reaction mixture
84
Q

oxidising primary alcohols to carboxylic acids
stage 4

A
  1. aldehyde stays in the reaction mixture and is oxidised to carboxylic acid
85
Q

oxidation of secondary alcohols

A

refluxing a secondary alcohol with acidified potassium dichromate(VI) will produce a ketone

86
Q

can secondary alcohols be oxidised into anything but ketones and why

A

ketones can’t be oxidised easily, so even prolonged refluxing won’t produce anything more

87
Q

how can you oxide tertiary alcohols

A

only way to oxidise tertiary alcohols is by burning them

88
Q

colour change when alcohols are mixed with acidified potassium dichromate(VI)

A

tertiary alcohols don’t react with acidified potassium dichromate(VI) at all- solution stays orange

Organic Chemistry (6 decks)

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