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Chemistry A-level - organic Chem > alcohols > Flashcards

alcohols Flashcards

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1
Q

what is the suffix of all alcohols ?

A

-ol

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2
Q

what is the general formula of alcohols ?

A

CnH2n + 1 OH

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3
Q

what is the functional group of alcohols ?

A

OH

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4
Q

what is the prefix/ name given to the functional group of alcohols if they are not the most important group in the molecule ?

A

hydroxy

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5
Q

what is it called when there are 2 alcohol functional groups in the molecule ?

A

diol

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6
Q

what is the additional subclass of all alcohols ?

A

primary alcohols
secondary alcohols
tertiary alcohols

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7
Q

how do you know if an alcohol is a primary , secondary or tertairy alcohol ?

A

you look at the carbon that is attached to the functional group and count how many carbons are attached to that specific carbon

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8
Q

what are the features of the bonds in alcohols ?

A
  • dipole dipole bonding
    oxygen is more electronegative than hydrogen
  • lone pair of electrons on oxygen
    so hydrogen bonds can form between lone pair and electron deficient hydrogen in a neighbouring alcohol
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9
Q

what is the melting and boiling point of alcohols ?

A

hydrogen bonds between molecules means alcohols have a higher melting point than alkenes

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10
Q

what is meant by solubility ?

A

the ability to dissolve in water

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11
Q

describe the solubility of alcohols and explain why is that the case ?

A

alcohols are soluble in water
- because they form hydrogen bonds with water
-but the longer an alcohol gets, the less soluble it becomes

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12
Q

what is the bond angle between the hydrogen bond and the O-H bond ?

A

always 180 degrees

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13
Q

which point are alcohols considered to be insoluble ?

A

from octan-1-ol
there is a gradual change before that

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14
Q

what is considered to be he most important alcohol ?

A

ethanol

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15
Q

what are the 2 different ways of producing ethanol ?

A
  • hydration of ethene
  • fermentation
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16
Q

what are the benefits of producing ethanol from crude oil and ethene ?

A
  • very fast method
  • the products of hydration are already pure
  • the method is a continuous process
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17
Q

what are the disadvantages of fermentation ?

A

-a very slow process
- products need to be distilled as it isn’t 100% pure
- batch process

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18
Q

state the overall equation for the hydration of ethene to produce ethanol ?

A

CH2 = CH2 + H2O —> C2H5OH

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19
Q

what reagent/ condition is essential for the hydration of ethene ?

A

a phosophuric acid catalyst must be added ( H3PO4)

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20
Q

show the hydration of ethene mechanism

A

picture is on your phone

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21
Q

how do you know that here was a catalyst present at the end of the hydration of ethene ?

A

because you are left with a H+ ion that was also there at the beginning
- this means it can be reused

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22
Q

state the overall equation for fermentation ?

A

C6H12O6 —->2 C2H5OH + 2 CO2

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23
Q

what are the reagents / conditions needed for fermentation ?

A
  • yeast
  • 35 degrees as a compromise because a high temp would speed up the reaction but also cause the enzymes to denature
  • anaerobic conditions ( no oxygen )
  • distillation of product to separate ethanol from the water as ethanol has a lower boiling point than water
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24
Q

what is happening in fermentation ?

A

it is the anaerobic respiration of the yeast

25
Q

what would occur if oxygen was present during fermentation ?

A

ethanol would be oxidised and it would produce ethanoic acid

26
Q

what is the boiling point of ethanol and what is the boiling point of water ?

A

ethanol = 78 degrees
water = 100 degrees

27
Q

what does it mean if something is carbon neutral ?

A

carbon dioxide taken in during the process = the carbon dioxide released during a process

28
Q

what is the process that takes in carbon dioxide needed for the process ?

A

photosynthesis

29
Q

is the process y which carbon dioxide is released ?

A

fermentation + combustion of the alcohol produced

30
Q

what is ethanol classified as ?

A

ethanol is a biofuel

31
Q

in what reactions is ethanol most commonly used in ?

A

used in combustion reactions

32
Q

what is the equation for the combustion of ethanol ?

A

C2H5OH + 6O2 —> 4CO2 + 6H2O

33
Q

what happens to the CO2 in all of the 3 processes ?

A

CO2 in = CO2 out

34
Q

why is the process of fermentation not completely carbon neutral even though it seems like it ?

A

because the processes involved in between the other processes such as transporting of the crops from one place to another releases co2 that is not considered in the equations

35
Q

what are the 2 main alcohol reactions ?

A
  • elimination reaction
  • oxidation
36
Q

what is meant by an elimination reaction ?

A
  • a reaction where a small molecule leaves a parent molecule
37
Q

what do alcohols always use in elimination reactions and other reactions ?

A

they always lose water (H2O)
the -OH is from the alcohol group
the -H is from the Carbon adjacent to the alcohol group

38
Q

what are all elimination reactions with alcohols also known as ? and why ?

A

dehydration reactions
- as we lose water

39
Q

what are the reagents and conditions for dehydration/ elimination reactions ?

A
  • 600K
  • Aluminium oxide catalyst (Al2O3)
40
Q

what is the test to make sure that you made an alkene during elimination reactions ?

A

bromine water
goes from yellow / orange to colourless

41
Q

what are the most common catalysts used in acid catalysed elimination ?

A

concentrated sulfuric acid (H2SO4)
concentrated phospohoric acid (H3PO4)

42
Q

what does the dehydration / elimination of primary alcohols result in ?

A

1 alkene

43
Q

what does the dehydration of a secondary alcohol result in ?

A

2+ alkenes
- due to isomeric products being made

44
Q

wat does the dehydration of a tertiary alcohol produce ?

A

results usually in mixtures

45
Q

what cannot happen to tertiary alcohols ?

A

they cannot be oxidised easily

46
Q

what is meant by oxidation ?

A

oxidation is the
- gaining of oxygen
- loss of hydrogen
- loss of electrons

47
Q

what does the oxidation of secondary alcohols result in ?

A

the oxidise to form ketones

48
Q

what does the oxidation of primary alcohols result in ?

A

they oxidise to form aldehydes
- and then they can be oxidised further into carboxyllic acids
- or, under the right conditions, they can be directly oxidised to form carboxylic acids

49
Q

what is added to the distillation flask and mixture ?

A

anti bumping granules
potassium dichromate
dilute sulfuric acid (H2SO4)

50
Q

what is the function of anti bumping granules ?

A

ensures that the boiling is no too violent

51
Q

what is the oxidizing agent in distillation ?

A

potassium dichromate
K2Cr2O7

52
Q

why does distillation work to produce the aldehyde ?

A

the strongest attraction in aldehydes is dipole-dipole whilst the alcohols have hydrogen bonding which is the strongest intermolecular force
so alcohols have a higher boiling point

53
Q

what are the conditions and reagents needed for the reflux reaction directly into a carboxylic acid ?

A
  • conc H2SO4
  • excess K2CR2O7
  • reflux
54
Q

what is the purpose of doing a reflux reaction ?

A
  • it allows you to carry out a reaction at the boiling point of the chemicals without losing any reactants or products
55
Q

what do you write instead of the formula for the oxidising agent in an oxidation equation ?

A

[O]

56
Q

2 ways for testing for an aldehyde

A
  • Warm , Fehling’s reagent
    observation = red precipitate
  • warm Tollen’s
    observation = silver mirror
57
Q

testing for a carboxylic acid

A

-add Na2CO3 ( sodium carbonate) solution or powder
observation = effervescence (fizzing) due to CO2 being produced

58
Q

testing for primary or secondary alcohols

A
  • add (acidified )potassium dichromate (K2CR2O7) and H2SO4 and warm it
    observation = orange to green colour change
59
Q

test for ketones

A

add Fehling’s reagent or Tollen’s and warm it
observation = no visible change
to prove it is not an aldehyde

Chemistry A-level - organic Chem (7 decks)

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