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chemistry > organic chemistry > Flashcards

organic chemistry Flashcards

1
Q

what is crude oil

A

remains of an ancient biomass consisting mainly of plankton that was buried in mud - high temp. and pressure converted these into crude oil

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2
Q

what is crude oil a mixture of

A

very large number of compounds, most of the compounds in crude oil are hydrocarbons

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3
Q

what is a hydrocarbon

A

molecules made up of hydrogen and carbon atoms only

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4
Q

what homologous series are most of the hydrocarbons in crude oil a part of

A

alkanes - saturated hydrocarbons

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5
Q

what does ‘saturated’ mean

A

each atom has formed bonds with as many other atoms as they can
- single bonds only

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6
Q

what is the general formula for alkanes

A

C(n)H(2n+2)

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7
Q

what are the first four alkanes

A

methane, ethane, propane and butane

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8
Q

what are the properties of mixtures

A
  • no chemical bonds between diff. parts of the mixture (diff. hydrocarbon molecules aren’t chemically bonded to one another)
  • all keep original physical properties such as their boiling points
  • properties of a mixture are a mixture of properties of the operate parts
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9
Q

how can we separate crude oil

A
  • can be separated out by physical methods
  • can be split up into its separate fractions by fractional distillation
  • each fraction contains molecules w/ a similar number of carbons to each other
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10
Q

describe the fractional distillation of crude oil

A

1) crude oil is vaporised and fed into bottom of column where its hottest
2) column gets cooler as you go up, vapour rises up
3) fractions condense off when they reach their boiling point
4) larger molecules condense at bottom
5) smaller molecules condense at the top

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11
Q

what can the fractions be processed for

A

produce fuels and feedstock for the petrochemical industry

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12
Q

what fuels can be made from crude oil

A

many of the fuels on which we depend for our modern lifestyle, such as petrol, diesel oil, kerosene, heavy fuel oil and liquefied petroleum gases

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13
Q

what materials are produced by petrochemical industry

A

solvents, lubricants, polymers, detergents

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14
Q

why do so many natural and synthetic carbon compounds occur

A

bc of the ability of carbon atoms to form families of similar compounds

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15
Q

what properties depend on the size of hydrocarbons

A

boiling point, viscosity, flammability - influence how hydrocarbons are used as fuels

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16
Q

what do small molecules have

A
  • less intermolecular forces
  • lower bp
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17
Q

what do large molecules have

A
  • more intermolecular forces
  • higher bp
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18
Q

the shorter the molecule…

A
  • the more runny the hydrocarbon is, or the less viscous it is
  • the more volatile they are ( turn into gas @ lower temp)
  • more flammable the hydrocarbon is
  • the cleaner the flame (less sooty, smoky it is)

longer hydrocarbons have opposite properties

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19
Q

why do we burn fossil fuels

A

burn coal, oil and natural gas to get energy for many processes

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20
Q

what happens during combustion

A

carbon and hydrogen react w/ oxygen in air so that carbon dioxide and water vapour are released into the atmosphere
- carbon and hydrogen are said to be oxidised and energy is released

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21
Q

what is combustion called when there is plenty of oxygen

A

complete combustion

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22
Q

what happens when a fuel is completely combusted

A

carbon dioxide and water vapour are produced

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23
Q

what is the equation for the complete combustion of a hydrocarbon

A

hydrocarbon + oxygen (g) -> carbon dioxide (g) + water vapour (g)

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24
Q

what can hydrocarbons be broken down into

A

smaller, more useful molecules

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25
Q

what is cracking

A

a thermal decomposition reaction - breaking down molecules by heating them

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26
Q

what are the diff. types of cracking

A

catalytic and steam cracking
(for both, the long chain hydrocarbon must be vaporised)

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27
Q

what is catalytic cracking

A

vaporisation long-chain alkane passed over hot, powdered catalysts (e.g. aluminium oxide). the long-chain molecules split, or crac on the surface of the catalyst

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28
Q

what is steam cracking

A

vaporised long-chain alkane is mixed with steam and heated to a v. high temp.

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29
Q

what are most of the products of cracking

A

smaller alkanes and unsaturated hydrocarbons called alkenes

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30
Q

why is cracking important

A
  • helps match supply of shorter alkanes w/ the demand for them
  • produces alkenes, which are useful as feedstock (raw materials) for the petrochemical industry (e.g. making plastics)
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31
Q

what are alkenes

A
  • hydrocarbons with a double carbon bond
  • more reactive than alkanes
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32
Q

what is the test for alkenes

A
  • reaction w/ bromine water
  • an alkene will decolourise it, turning it from orange to colourless.
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33
Q

why are alkenes called unsaturated hydrocarbons

A

contain 2 fewer hydrogen atoms than alkane with the same number of carbon atoms

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34
Q

what is the general formula for alkenes

A

C(n)H(2n)

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35
Q

what are the first four alkenes

A

ethene, propene, butene, pentene

36
Q

what is the. functional group of alkenes

A

C=C

37
Q

what type of combustion do alkenes tend to undergo

A

incomplete combustion (unless there us enough O2)
- produces an orange smoky flame

38
Q

what is the general equation for the incomplete combustion of alkenes

A

alkene + oxygen -> carbon dioxide + carbon monoxide + carbon + water vapour
- releases less energy than complete combustion

39
Q

what are addition reactions of alkenes

A

where two molecules combine and form only one product. the double bond opens up and two atoms (or group of atoms) are added

40
Q

what is hydrogenation

A

ADDITION OF HYDROGEN:
- when an alkane reacts w/ hydrogen gas , two hydrogen atoms are added across/ on either side of the double bond. the corresponding saturated alkane is the products

41
Q

what is a halogenation reaction

A

ADDITION OF HALOGENS:
- when an alkene reacts with halogens (bromine, iodine, chlorine etc.) each carbon atom at the double bond gains a halogen atom

(does not matter where u draw them, but make sure there is only one halogen on each carbon atom)

42
Q

what is a hydration reaction

A

ADDITION OF WATER:
- when alkenes react w/ steam, water is added across the double bond: H on one carbon atom and OH on the other. the product is an alcohol
- a catalyst is needed for this reaction.

43
Q

what happens when propene or butene undergo a hydration reaction

A

propene + butene:
- diff. alcohol compounds can be made depending on which C the -OH group bonds w/.

44
Q

what functional group do alcohols contain

A

-OH

45
Q

what is the general formula for alcohols

A

C(n)H(2n+1)OH

46
Q

what are the first four alcohols

A

methanol, ethanol, propanol, butanol

47
Q

where is ethanol found

A

alcoholic beverages such as beer and wine

48
Q

what has ethanol been used for recently

A

as a biofuel additive to regular automobile fuel such as petrol. (some run on ethanol alone)

49
Q

how is ethanol produced

A

fermentation
- aqueous solutions of sugars are added to yeast, anaerobically

50
Q

what is the equation for fermentation

A

glucose -> ethanol + carbon dioxide

51
Q

what are the conditions for the fermentation of yeast

A
  • warm temps. (25-35°C) necessary so reaction isn’t too slow
  • when temps. are hotter, enzymes denature (no longer function = no fermentation)
52
Q

describe the process of fermentation

A

1) a crop is harvested
2) process the crop into smaller pieces
3) starch/cellulose broken down into glucose
4) sugars and yeast are added in container and CO2 is allowed to escape but air is prevented from entering
5) sugars are fermented
6) the ethanol is distilled to purify it

53
Q

what is methanol used for

A

as a chemical feedstock

54
Q

what is ethanol used for (generally)

A
  • drinks
  • as a solvent
55
Q

what is propanol used for

A
  • as a solvent
  • fuel
56
Q

what is butanol used for

A
  • as a solvent
  • fuel
57
Q

what are methylated spirits

A

(denatured alcohol) mostly ethanol but contain toxic methanol and other ingredients.
- excellent solvent
- purposely dyed purple and foul smelling and tasting additives are added to deter people from consuming it

58
Q

what happens when an alcohol reacts w/ the oxygen in the air

A

undergoes complete combustion (an oxidation reaction) to produce carbon dioxide and water

59
Q

what happens when ethanol reacts with air

A

ethanol + oxygen -> carbon dioxide + water

60
Q

what happens when there isn’t sufficient enough oxygen when reacting with an alcohol

A

incomplete combustion will occur

61
Q

what happens when an alcohol and sodium react

A

an alkoxide and hydrogen gas are formed

62
Q

what is the general equation for the reaction of sodium and an alcohol

A

alcohol + sodium -> sodium alkoxide and hydrogen gas

63
Q

what alcohols are completely miscible (soluble) in any proportion

A

the first three - methanol, ethanol, propanol

64
Q

what is butanol’s solubility in water

A

not soluble in any proportion - only slightly soluble

65
Q

what happens when a large amount of butanol is added to water

A

only a specific (max.) amount will dissolve in a given vol. of water. the rest will remain undissolved as a separate layer.

66
Q

what happens to an alcohol’s solubility when it has a longer carbon chain length than 3

A

becomes increasingly less soluble

67
Q

what is an oxidising agent

A

oxidises another substance/ causes another substance to lose electrons

68
Q

what happens when an alcohol reacts with an oxidising agent

A

a carboxylic acid and water is formed

69
Q

what is the general equation for the reaction of an alcohol with an oxidising agent

A

alcohol + oxidising agent -> carboxylic acid + water

70
Q

what happens when ethanol reacts with an oxidising agent

A

ethanol + oxidising agent -> ethanoic acid + water

71
Q

what functional group do carboxylic acids have

A

-COOH

72
Q

what are the first 4 carboxylic acids

A
  • methanoic acid
  • ethanoic acid
  • propanoic acid
  • butanoic acid
73
Q

what is the general formula for carboxylic acids

A

C(n)H(2n+1)COOH

74
Q

why are carboxylic acids weak

A

they only partially dissociate in water

75
Q

what happens when you dissolve carboxylic acids in water

A

CH3COOH -> CH3COO(-) + H(+)

76
Q

what happens when you react a carboxylic acid with a carbonate

A

an ethanoate, water and carbon dioxide are formed
- an example of a neutralisation reaction

77
Q

what happens when you react ethanoic acid with sodium carbonate

A

ethanoic acid + sodium carbonate -> sodium ethanoate + water + carbon dioxide (bubbles show reaction)

78
Q

what happens when carboxylic acids undergo neutralisation reactions w/ a base

A

form a salt and water

79
Q

what happens when carboxylic acids react with metals

A

produce salt and hydrogen

80
Q

what happens when a carboxylic acid reacts with an alcohol

A

an ester and water are produced

81
Q

what is the general equation for the reaction between a carboxylic acid and an alcohol

A

carboxylic acid + alcohol -> ester + water

82
Q

give the reaction equation between ethanoic acid and ethanol

A

ethanoic acid + ethanol -> ethyl ethanoate + water

83
Q

what is an ester and its functional group

A

group of organic compounds with the functional group -COO

84
Q

what are esters used for

A

as they smell fruity they can be added to products to give them a fruity aroma or smell, often added to polymers

85
Q
A

chemistry (9 decks)

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