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chem spec > organic chemistry > Flashcards

organic chemistry Flashcards

1
Q

what resource is crude oil and where is it found

A

a finite resource found in rocks

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2
Q

what is crude oil

A

the remains of an ancient biomass consisting mainly of plankton that was buried in mud

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3
Q

what is crude oil a mixture of

A

a very large number of compounds, mostly hydrocarbons

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4
Q

what are hydrocarbons

A

molecules made up of hydrogen and carbon atoms only

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5
Q

general formula for homologous series of alkanes

A

CₙH₂ₙ₊₂

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6
Q

first four alkanes

A

Mouses Eat Peanut Butter

Methane, Ethane, Propane, Butane

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7
Q

define a homologous series

A

a series of hydrocarbons with similar properties and that react in a similar way

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8
Q

what compounds are alkanes and why

A

saturated compounds because they have no double bonds (all of its electrons are being used for bonding)

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9
Q

what type of bonding is in hydrocarbons

A

covalent, because both atoms are non-metals (hydrogen and carbon)

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10
Q

what can the hydrocarbons in crude oil be separated into

A

fractions, each of which contains molecules with a similar number of carbon atoms, by fractional distillation

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11
Q

what can the fractions be processed to produce

A

fuels and feedstock for the petrochemical industry

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12
Q

what oils are produced from crude oil (in order from top to bottom of fractional column)

A

many of the fuels on which we depend for our modern lifestyle, e.g., liquefied petroleum gases (camping stoves), petrol (cars), kerosene (jet fuel), diesel oil (larger cars and vans) and heavy fuel oil (ships)

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13
Q

what is produced by the petrochemical industry

A

many useful materials on which modern life depends, such as solvents, lubricants, detergents and polymers

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14
Q

why is there a vast array of natural and synthetic carbon compounds

A

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

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15
Q

why do we separate the different hydrocarbons in crude oil

A

because they all contain different properties useful for different purposes - crude oil without separation is useless

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16
Q

method for separating crude oil

A

fractional distillation
1) heat crude oil until becomes vapour and feed it into fractionating column - hot at bottom, cooler at top
2) each fraction of hydrocarbon gases within the vapour condense into liquid at different points along the fractionating column bc they all have different boiling points so will condense at different temps
3) this separates the crude oil into diff fractions, each with similar number of carbon atoms
4) longer chain hydrocarbons have higher boiling points bc larger molecule so condense into liquid at bottom of column, while shorter chain hydrocarbons have lower boiling points so condense at top of column - some won’t condense at all and will remain gas, producing LPG (liquified petroleum gas)

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17
Q

factors affecting properties of hydrocarbons

A

size of molecules:
- boiling point
- viscosity
- flammability

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18
Q

how does fractional distillation for crude oil work

A

each fraction of hydrocarbons has diff boiling point so condenses at diff heights of column

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19
Q

how does viscosity affect properties of hydrocarbons

A

more viscous fluid flows more slowly
- as size of hydrocarbon molec increases, viscosity increases

TO HELP REMEMBER (dont say in exam)
- bigger = more intermolecular forces so stick together and more viscous

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20
Q

how does flammability affect properties of hydrocarbons

A

tells us how easily hydrocarbon combusts
- as size of hydrocarbon molec increases, flammability decreases, so short chain hydrocarbons v flammable

TO HELP REMEMBER
methane is main component in natural gas used to heat homes - high flammability, short chain hydrocarbon

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21
Q

how does boiling point affect properties of hydrocarbons

A

temperature when liquid -> gas
- as size of hydrocarbon increases, boiling point increases, so short chain hydrocarbons are gases at room temp

TO HELP REMEMBER
methane is gas so very low boiling point

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22
Q

what does the combustion of hydrocarbon fuels release

A

energy

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23
Q

what happens during combustion of hydrocarbons

A

the carbon and hydrogen in the fuels are oxidised, because the hydrogen is combining with oxygen to form water and the carbon is combining with the oxygen to form carbon dioxide

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24
Q

equation for complete combustion of a hydrocarbon

A

hydrocarbon + oxygen -> carbon dioxide + water

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25
Q

what type of reaction is complete combustion

A

exothermic as lots of energy is released in the process

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26
Q

what is cracking

A

hydrocarbons being broken down to produce smaller, more useful molecules

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27
Q

why is cracking important

A

long-chain hydrocarbons tend to have much lower demand, as they are less flammable than short-chain so less effective as fuels

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28
Q

what is the issue with high demand for short-chain hydrocarbons and how is this resolved

A

most hydrocarbons found in crude oil are long-chain - so to meet demand and produce more useful molecule, they undergo cracking

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29
Q

two methods used for cracking

A
  • catalytic cracking; high temp and catalyst
  • steam cracking; high temp and steam
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30
Q

what is catalytic cracking

A

we pass the hydrocarbon vapour over a hot catalyst causing the long-chain hydrocarbon to split into two or more shorter hydrocarbons

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31
Q

what is steam cracking

A

we mix the hydrocarbon vapour with steam and heat it to a very high temperature in order to split it into two or more shorter hydrocarbons

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32
Q

what is the difference between alkanes and alkenes

A

alkenes have a double bond (C=C) whereas alkanes only have single bonds - this means alkanes are saturated whereas alkenes are unsaturated molecules

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33
Q

why are alkenes more reactive than alkanes

A

alkenes are unsaturated, meaning this double bond can open up and bond to 2 other atoms, making it more reactive

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34
Q

what are the products of cracking

A

alkanes and alkenes

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35
Q

what do alkenes react with

A

bromine water

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36
Q

what is the positive test for alkenes

A

adding bromine water to a solution - if it turns from orange to colourless, alkenes are present

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37
Q

why does bromine water remain orange in the presence of alkanes

A

alkanes are saturated so cannot react with bromine

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38
Q

what are alkenes used for

A
  • to produce polymers
  • as starting materials for the production of many other chemicals
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39
Q

how can alkenes produce polymers

A

the double bond means that alkenes can bond together to form polymers bc double bond breaks up to form 2 bonds that allow alkene to bond to adjacement molecules

40
Q

what are alkenes

A

hydrocarbons with a double carbon-carbon bond

41
Q

general formula for homologous series of alkenes

A

CₙH₂ₙ

42
Q

why are alkene molecules unsaturated

A

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

43
Q

first four members of the homologous series of alkenes

A

Elephants Pack Butter Pants
ethene, propene, butene and pentene

44
Q

functional group of alkenes

A

C=C

45
Q

what determines the reactions of organic compounds

A

the generality of reactions of functional groups

46
Q

how many bonds can a carbon atom have in alkenes

A

4

47
Q

why can alkenes undergo addition reactions

A

because the C=C bond can open up to allow it to bond to 2 more atoms of another molecule, so we can add other molecules to the alkene

48
Q

describe the reaction of an alkene with hydrogen gas

A

in the presence of a nickel catalyst and heat, it will form an alkane because the double bond will break apart to bond with the 2 extra hydrogen atoms to form the alkane counterpart which is saturated (no double bond)

e.g. pentene can undergo hydrogenation to form pentane

49
Q

describe the reaction of an alkene with water (steam)

A

in the presence of a catalyst and high temps (water vapour) to produce an alcohol, because the double bond breaks apart to react to the H and Oh to form an OH functional group and an extra hydrogen atom
HENCE we need a catalyst, high temperatures and high pressures

50
Q

properties of an alcohol produced from an alkene reaction

A
  • saturated
  • no double bonds
51
Q

what is the functional group of an alcohol

A

-OH

52
Q

how can we industrially produce ethanol

A

the alkene reaction with steam is reversible, so any unreacted ethene gas is recycled back into the reactor

53
Q

describe the reaction of alkenes with halogens

A

similar to hydrogen except no catalyst or temperature or pressure required. most common example is reacting ethene with bromine to form dibromoethane (colourless). as bromine used up, alkene causes colour change from orange to colourless; the two halogen atoms have added across double bond, making it single bond

54
Q

describe the combustion of alkenes in air

A

it produces unburnt carbon particles due to incomplete combustion, meaning they burn in air with smoky flames. they produce carbon monoxide and carbon in addition to carbon dioxide and water

55
Q

when would alkenes completely combust

A

in the presence of a large amount of oxygen, but with air, some incomplete combustion also takes place

56
Q

incomplete combustion equation

A

alkene + oxygen -> carbon dioxide + water + carbon monoxide + carbon

57
Q

first four members of a homologous series of alcohols

A

methanol, ethanol, propanol, butanol

58
Q

why are alcohols not hydrocarbons

A

bc they contain oxygen

59
Q

difference between alkanes and alcohols

A

they look identical except alcohols have an -OH functional group instead of one of the hydrogens

60
Q

evaluate of hydration of ethene

A

PROS
- produces a high yield of ethanol

CONS
- requires high temp so lots of energy
- therefore expensive and less cost-effective
- ethene comes from non-renewable crude oil, will run out

61
Q

how can we produce aqueous solutions of ethanol other than hydration of ethene

A

when sugar solutions are fermented using yeast

62
Q

describe fermentation of sugar using yest

A

at 30º, anaerobic conditions and in the presence of yeast, glucose breaks down to form ethanol and carbon dioxide

63
Q

evaluate production of ethanol via fermentation

A

PROS:
- low temp means not a lot of energy needed
- sugar comes from plants so renewable resource

CONS:
- product is an aqueous solution of ethanol, so to extract it, we need to carry out distillation which requires heat energy

64
Q

fermentation of ethanol equation

A

sugar —(yeast)—> carbon dioxide + ethanol

65
Q

properties of alcohol

A
  • very flammable unlike alkenes
  • therefore undergo complete combustion when burned in air
  • produce carbon dioxide and water in complete combustion reactions
66
Q

how do you balance combustion equations of alcohols

A
  • start by balancing the carbon atoms
  • then the hydrogen atoms
  • then the oxygen atoms
67
Q

what are alcohols soluble in

A

aqueous solutions and produce pH7 solutions

68
Q

functional group of carboxylic acids

A

-COOH

69
Q

first four members of a homologous series of carboxylic acids

A

methanoic acid, ethanoic acid, propanoic acid, butanoic acid

70
Q

what happens when we add an oxidising agent to an alcohol

A

we produce a carboxylic acid and water

71
Q

what happens when we react alcohols with sodium (use example of ethanol)

A

sodium ethoxide and hydrogen gas are produced, so we would observe effervescence

72
Q

why are carboxylic acids weak in terms of ionisation and pH

A

they only partially ionise when dissolved in aqueous solutions, meaning not all carboxylic acid molecules will dissociate and produce H+ ions; relatively low conc of H+ ions produced in comparison to a strong acid, hence has a higher pH than a strong acid of the same concentration

73
Q

what happens when a carboxylic acid reacts with carbonates

A

acid + carbonate -> salt + water + carbon dioxide

74
Q

what happens when a carboxylic acid reacts with alcohols

A

an ester and water are produced
e.g. ethanoic acid + ethanol -> ethyl ethanoate

75
Q

why are esters really useful molecules

A
  • pleasant smell
  • often used in food flavourings and perfumes
  • volatile (evaporate easily)
76
Q

what can alkenes be used to make

A

polymers by addition polymerisation

77
Q

how is a polymer formed

A

by joining lots of small, identical repeating units called monomers

78
Q

2 types of polymers

A
  • addition polymers
  • condensation polymers
79
Q

in an addition polymer what will the monomer always be and why

A

an alkene because alkenes have a double bond so can open it up to react with adjacent alkene molecules to form the polymer

80
Q

why in addition polymers does the repeating unit have the same atoms as the monomer

A

because no other molecule is formed in the reaction

81
Q

suffixes for all groups e.g., alcohols, carboxylic acids

A

ALCOHOLS:
- ol
- diol (CP)

CARBOXYLIC ACIDS
- oic
- dioic (CP)

82
Q

what does condensation polymerisation involve

A

monomers with two functional groups (meaning they’re not alkenes like AP)

83
Q

what happens when the monomers of condensation polymers react

A

small molecules such as water are usually lost, making them condensation reactions

84
Q

how are the simplest polymers produced

A

from two different monomers with two of the same functional groups on each monomer

85
Q

what is glycine

A

an example of an amino acid

86
Q

what do all amino acid molecules have

A

two different functional groups e.g., glycine has the amino and carboxyl group

87
Q

how do amino acids produce polypeptides

A

they react by condensation polymerisation

88
Q

how are proteins produced

A

by combining different amino acids in the same chain

89
Q

how can we tell that a condensation polymer is formed

A

because a small molecule (usually water) is produced

90
Q

what happens when you react a lot of glycine molecules in a condensation polymerisation reaction

A

we form a glycine polypeptide

91
Q

DNA stands for

A

deoxyribonucleic acid

92
Q

what is DNA

A

an example of a large naturally-occurring polymer essential for life

93
Q

what does DNA encode

A

genetic instructions for the development and functioning of living organisms and viruses

94
Q

structure of DNA molecules

A

they’re two polymer chains, made from four different nucleotide monomers (ATGC) in the form of a double helix

95
Q

examples of naturally occurring polymers important for life

A
  • DNA
  • protein
  • starch
  • cellulose
96
Q

what monomers make up proteins

A

amino acids

97
Q

what monomers make up starch and cellulose

A

glucose

chem spec (12 decks)

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