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Chemistry Y12 > Organic chemistry > Flashcards

Organic chemistry Flashcards

1
Q

what is nomenclature?

A

describing, classifying,naming organic compounds

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2
Q

Sumarise isomerism?

A

isomers are substances that have the same molecular formula but a different arrangement of atoms

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3
Q

what are organic molecules

A

contain carbon and hydrogen e.g hydrocarbons

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4
Q

what type of bonding occurs in organic molecules?

A

mainly covalent bonds

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5
Q

what other atoms does carbon form covalent bonds with?

A

Carbon, hydrogen, nitrogen, oxygen, halogens

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6
Q

if bonds are non-polar..?
if bonds are polar..?

A
  • electrons are shared equally
  • electrons are shared unequally
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7
Q

are bonds between the C-C and the C-H polar or non-polar?

A

non-polar

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8
Q

what type of bonding occurs between C-N, C-O, C-Halogen?

A

polar bonding

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9
Q

what does bond polarity determined

A

the way organic molecules react

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10
Q

why are alkanes saturated?
why are alkenes unsaturated?

A
  • alkanes are molecules containing a single bond
  • alkenes are molecules containing a double bond
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11
Q

why are molecules said to be unsaturated?

A

because we can add more atomss/groups across the double bond

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12
Q

carbon atoms that are arranged in chains are called

A

aliphatic molecules

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13
Q

carbon atoms that are arranged in rings are called?

A

cyclical structures

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14
Q

what is the molecular formula?

A

finds the actual number of atoms of each element present in the molecule

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15
Q

what is the displayed/structural formula?

A

shows all the atoms and all the bonds present in the molecule

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16
Q

what is the abbreviated structural formula?

A

used when balancing equations e.g CH3CH20H

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17
Q

what is the skeletal formula?

A

only shows the bonds of the carbon skeleton
drawn as a zig zag

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18
Q

What is the empirical formula?

A

the empirical formula of a compound is the simplest whole number ratio of atoms of each element present in the molecule

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19
Q

Empirical Formula Calculations

A
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20
Q

How do we calculate empirical formula calculations?

A

we can find the empirical formula of a compound from percentages or masses by using the following method:
- list all elements in the compound
- underneath, write their experimental percentage or mass
- divide each percentage or mass by the Ar for that particular element
- turn the numbers you get into simple ratios and into it’s simplest form

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21
Q

form the empirical formula we can work out the..?

A

molecular formula

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22
Q

question 1: A hydrocarbon W, contains 92.3% carbon by mass. the relative molecular mass of W is 78. Calculate the empirical and molecular formula of W.

A

empirical - 1:1 (CH)
molecular - C6H6

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23
Q

Question 2: Compound A (Mr=58) has a percentage composition by mass of: C=62.04% H=10.41% O=27.55%
Calculate the molecular formula of A

A

empirical + molecular formula - C3H6O

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24
Q

A chloroalkane, Z was shown to contain 37.2 carbon and 55% chlorine by mass. the remainder was Hydrogen. Calculate the empirical formula of compound Z

A

C2H5Cl

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25
Q

b) what additional information would be needed to calculate the molecular formula of compound Z?

A

would need the molecular mass

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26
Q

What is the functional group?

A

Is an atom or group of atoms that determine the chemical properties of the molecule

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27
Q

What part of the molecule is it?

A

The reactive part of the molecule

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28
Q

If an organic molecule has the same functional group they behave…?

A

Chemically in a similar way

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29
Q

What is the homologous series?

A

A name given to a family of molecules that can be represented by a general formula

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30
Q

All member of homologous series have the same functional group but..?

A

An increasing number of carbon atoms

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31
Q

Each successive molecule contains an additional…?

A

-Ch2- group

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32
Q

What do the homologous series show?

A

Gradual trend in physical in physical properties as carbon chain gets longer

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33
Q

Longer the hydrocarbon chain the..?

A

Higher the boiling point

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34
Q

What does the general formula not work for?

A

Cyclical structures

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35
Q

Why do aldehydes and ketones have the same general formula?

A

They are functional group isomers

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36
Q

Explain the structure of methane (3D and normal)
Bond angle?
Shape?

A

Arrangement of bonds is tetrahedral
Bond angle = 109.5
Atoms rotate freely
Occurs in all saturated molecule

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37
Q

Why do alkanes have a relatively low boiling point?

A

Have weak forces of attraction (weak van Der Waals forces between neighbouring molecules therefore have a low boiling point

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38
Q

Why does the boiling point increase as Alkane chain gets bigger?

A

As the size of alkane molecule increases the strength of Van Der Waals forces between the molecules increases (increased contact between neighbouring molecules so the bp increases so more energy must be supplied to release individual molecules as a gas

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39
Q

What is petroleum a mix of?
Separated by?

A
  • mix of mainly alkanes
  • separated by fractional distillation
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40
Q

What are structural isomers?

A

Compounds with the same molecular formula but different structural formula

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41
Q

3 different types of structural isomers

A

Chain isomers, positional isomers and functional group isomers

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42
Q

What is chain isomerism?

A

When there are 2 or more ways of arranging the carbon skeleton of a molecule (same molecular formula - different carbon skeleton)

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43
Q

The hydrocarbon chain can be either be…?

A

Branched or unbranched

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44
Q

Why do they share similar chemical properties?

A

They belong to the same homologous series

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45
Q

What differs?

A

Their physical properties

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46
Q

Why do branched-chain isomers have a lower bp?

A

Van Der Waals forces are weaker/ molecules are more spherical so fewer points of contact between neighbouring molecules

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47
Q

Chain isomers occur in all carbon compounds containing?

A

4+ carbon atoms

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48
Q

What is positional isomerism?

A

Have the same molecular formula the same carbon skeleton and same functional group but the functional group is joined at a different position on the carbon skeleton

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49
Q

Because of the different positions it can cause..?

A

Some differences in properties

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50
Q

What is functional group isomerism?

A

Have the same molecular formula but different functional group so belong to different homologous series

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51
Q

Since they have different functional groups they have?

A

Different chemical and physical properties

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52
Q

What kind of finite/non renewable resource is crude oil/petroleum

A

Fossil fuel

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53
Q

What is petroleum?
What is it a mixture of?
Type of Hydrocarbons?

A

A sticky and tary substance
Complex mixture of hydrocarbons (main straight chain alkanes)
Alkanes , cycloalkanes, aromatic hydrocarbons

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54
Q

How is crude oil/ petroleum formed?

A
  • Formed from dead remains of vast numbers of tiny sea creatures and plants which sank to the bottom of the ocean and were covered by layers of sedimentary rock,
  • as layers increased so did pressure and temperature
  • under high pressure (created by weight of overlaying rock) and temperature (generated by decomposition) and absence of air/oxygen
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55
Q

What did this do?
What was oil absorbed by?
Why did the oil migrate upwards?

A
  • Converted the organic material into oil and gas
  • porous rock
  • oil is less dense than water soo migrated upwards until trapped under impermeable rock
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56
Q

How do we extract crude oil?
How does natural gas stay under the surface?

A
  • Drill into the ground (‘traps’) and pull it up to the surface
  • forms a pocket at surface of oil reservoirs
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57
Q

How do we separate crude oil?
What type of process is fractional distillation?

A
  • by fractional distillation
  • physical process
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58
Q

Explain how different hydrocarbons are extracted from petroleum by fractional distillation?

A
  • crusted oil is heated until vaporised
  • the hydrocarbon vapour is then passed into a fractionating column
  • the column is kept at a very high temperature at the bottom (350) and cooler toward the top
  • the largest hydrocarbons remain liquids at temperatures as high as 350, they fall to the bottom of the column as residue
  • the smaller hydrocarbons rise up the column in a gaseous state.
  • as a particular hydrocarbon reaches the level in the column where temperature is equal to boiling point, it condenses and is collected
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59
Q

What type of hydrocarbons reach the top of the colum

A

Only the most volatile hydrocarbons reach the top of the column

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60
Q

How is the liquid collected?
What do the bubble caps do?
When vapour arrive at a tray that is sufficiently cool..?

A
  • In a series of trays contains bubble caps
  • force the rising vapours to pass through the liquid in the trays
  • the vapours condense to a liquid then piped off separately
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61
Q

What is the fractionating responsible for ?
Explain why?

A
  • primary distillation
  • primary distillation does not separate individual hydrocarbons each fraction contains a mixture of hydrocarbons that have boiling points within a specific range
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62
Q

How can they be further separated?

A
  • via secondary distillation to obtain purer products
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63
Q

After primary distillation the fractions are treated in several ways?

A
  • some sulfur is removed to reduce the amount of pollution produced when the fractions used as fuels are burned in car engines
  • some of the fraction is cracked to produce useful products
  • residue is further distilled
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64
Q

What is vaccum distillation?

A

Allows the mixture to be separated at temperature below its normal boiling point - prevents components decomposing

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65
Q

Why do we use vaccum distillation?

A

At high temperature some components in residue decompose/ break down

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66
Q

Properties of short hydrocarbons
Properties of long hydrocarbons

A
  • low bp, light in colour, highly flammable, low viscosity , more volatile
  • high bp, dark in colour, low flammability, high viscosity, less volatile
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67
Q

Explain why shorter straight chain hydrocarbons have low boiling points?

A

Have weak Van Der Waals forces between neighbouring molecules so fewer points of contact so not much energy required to break forces so generally have low bp

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68
Q

Why do longer straight chain hydrocarbons have a higher boiling point?

A

Have stronger Van Der Waals forces between neighbouring molecules more points of contact so more energy required to break therefore has a boiling point

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69
Q

what are most fractions used for?
Why might some fractions be too valuable to burn?

A
  • fuels.
  • But petroleum is a finite resource, so when supplies become more limited may become to valuable to burn
70
Q

which two substances are more likely to be cracked?

A

Naphtha and kerosine

71
Q

what are the uses of Alkenes and Aromatics?

A

are useful starting materials (feedstock) for the petrochemical industry

72
Q

what can they be converted into..?

A

important products such as plastics, dyes, detergents, medicines, paints and insecticides

73
Q

Describe the boiling point, uses and approximate number of carbon atoms of liquified petroleum gas?

A

Bp - up to 25
Uses - gas cookers, gas fires, camping gas
n - 1-4

74
Q

Describe the boiling point, uses and approximate number of carbon atoms in Petrol

A

Bp - 40-100
uses - petrol
n - 4-12

75
Q

Describe the boiling point, uses and approximate number of carbon atoms in naphtha?

A

bp - 100-150
uses - petrochemicals
n - 7-14

76
Q

Describe the boiling point, uses and approximate number of carbon atoms in kerosine (paraffin)

A

bp - 150-250
uses - jet fuel, petrochemicals
n - 11-15

77
Q

Describe the boiling point, uses and approximate number of carbon atoms in gas oil (diesel)

A

bp - 220-350
uses - transport fuel, central heating fuel, petrochemicals
n - 15-19

78
Q

Describe the boiling point, uses and approximate number of carbon atoms in mineral/lubricating oil?

A

bp - <350
uses - lubricating oil and petrochemicals
n - 20-30

79
Q

Describe the boiling point, uses and approximate number of carbon atoms in fuel oil?

A

Bp - over 400
Uses - fuel for ships and power stations
n - 30-40

80
Q

Describe the boiling point, uses and approximate number of carbon atoms in wax, grease

A

bp - over 400
uses - candles, grease for bearings, polishing waxes
n - 40-50

81
Q

Describe the boiling point, uses and approximate number of carbon atoms in Bitumen (tar)?

A

Bp - over 400
uses - roofing, road surfacing
n - above 50

82
Q

what is cracking?

A

large alkane molecules are broken down into more shorter more useful molecules

83
Q

why are shorter molecules more in demand?

A

more useful, used in petrol

84
Q

cracking breaks down…?

A

c-c bonds and (c-h)

85
Q

write an equation for cracking?

A

large alkane —> smaller alkanes + alkenes +(hydrogen)

86
Q

why may we need to separate mixtures by fractional distillation (after cracking)?

A

when cracked molecules can break up in a number of different ways to form a mixture of hydrocarbons

87
Q

these products will always contain less…?

A

carbon atoms than the original

88
Q

what are the reaction conditions required for thermal cracking

A
  • High temperature (400-900 C) and
  • (High pressure) 7000kpa or 70atm
  • In the absence of Oxygen
89
Q

what is thermal cracking?

A

produces shorter alkanes and a high percentage of alkenes

90
Q

why do we have to do thermal cracking in the absence of air?

A

otherwise alkane combustion will occur

91
Q

why are more c-c bonds broken ?

but at very high temperatures..?

A

c-c bonds are weaker (lower bond energy) than c-h bonds so more c-c bonds = broken

  • c-h bonds break and hydrogen is formed
92
Q

why is there a high proportion of shorter chain alkanes?

A

as temperature increases the carbon chain breaks nearer towards the end of the chain

93
Q

how do we avoid the decomposition of alkanes?

A

limit the time they are exposed to high temperatures

94
Q

what is the exposure time a.k.a and what is it?

A

residue time and approximately 1second

95
Q

why is thermal cracking expensive?

A

requires high temperature and pressure so requires an expensive reaction vessel

96
Q

thermal cracking occurs via a..?

A

a free-radical mechanism

97
Q

what is a radical?

A

is a species with an unpaired electron

98
Q

thermal cracking is started by..?
to form..?

A
  • the homolytic fission of a c-c bond
  • 2 alkyl radicals
99
Q

what happens in homolytic fission?

A

in homolytic fission the bond breaks equally and each carbon atom from the c-c bond gets one of the covalently shared electrons

100
Q

what is octane used in?
what is ethane used in?

A
  • petrol
  • to make plastics and antifreeze
101
Q

what is catalytic cracking?
mainly used to produce..?

A

takes place at slight pressure, high temperature and in the presence of a zeolite catalyst, mainly used to produce motor fuels and aromatic hydrocarbons

102
Q

how does a catalyst work?

A

reduces the activation energy required for te reaction so less energy is required

103
Q

what happens in the catalytic cracker?

A
  • hydrocarbons are vapourised
  • mixed with a zeolite catatlyst
104
Q

zeolites are synthetic which means..?
they’re also …?

A

they’re man-made
modern catalysts

105
Q

what is meant by catalysts are crystalline alluminosilicates?

A

they contain atoms of silicon, oxygen and aluminium

106
Q

structure of a zeolite
why can the pore size be altered?

A
  • series of pores and interconnecting chanels which create a large SA
  • to accommodate hydrocarbon molecules which are cracked inside the structure
107
Q

large alkanes are cracked to produce…?

A

mainly branched alkanes, cycloalkanes and aromatic hydrocarbons

108
Q

since the proportion of alkenes produced is small this type of cracking is primarily used for…?

A

producing motor fuels and a major method for producing petrol

109
Q

what are important components in petrol?

A

small branched chain alkanes and aromatic hydrocarbons

110
Q

branched chain alkanes help…?

A

the fuel to burn more smoothly and therefore prevent petrol engine auto-ignition (knocking)

111
Q

how can high pressure cause ‘knocking’?

A

may cause the fuel air to mix to ignite before the spark is produced

112
Q

in the past how was ‘knocking’ reduced explain why this is bad?

A

knocking was reduced in the past by adding lead components but now we know that lead can case pollution

113
Q

catalytic cracking occurs via..?

A

a mechanism that involves carbocation intermediate

114
Q

what is carbocation?

A

a molecule containing a positively charged carbon atom

115
Q

how many covalent bonds does a positive carbon make?

A

3 covalent bonds

116
Q

how does a zeolite function as a molecular sieve?

A

zeolites pores are small enough to allow straight chain alkanes to pass but branched chain molecules can not pass through as they are too bulky

117
Q

zeolite is used to separate?

A

unbranched hydrocarbons that are used to make biodegradeable detergents

118
Q

what is a fuel?

A

a substance that is burnt to release energy

119
Q

what type of reaction is combustion?

A

exothermic

120
Q

what happens in alkane combustion

A

alkanes heated in air to overcome the activation energy

121
Q

combustion of octane equation?

A

C8H18 + 12.5o2 —-> 8co2 + 9h2o

122
Q

why does this reaction have a high activation energy?

A

strong c-c and c-h bonds must be broken

123
Q

where is the energy to overcome the activation energy supplied?

A

from a spark in the internal combustion engine

124
Q

explain why the reaction is highly exothermic?

A

the energy released in the bond making is more than enough to compensate for the activation energy

125
Q

what is complete combustion?

A

occus in a plentiful supply of oxygen

126
Q

what is the equation for complete combustion?

A

ch4 + 2o2 —> co2 + 2h20

127
Q

as the number of carbon atoms increases..?

A

more oxygen is needed per alkane molecule and the reactions are more exothermic

128
Q

how does incomplete combustion occur?

A

in an insufficent supply of oxygen the products are carbon monoxide and water but in some cases c-soot is formed

129
Q

what are the two equations for incomplete combustion?

A

CH4 + o2 —-> c + 2H20
C4H10 +4.5O2 —> 4CO + 5H20

130
Q

how is carbon monoxide released into the atmosphere?

A

from exhausts of petrol engine vehicles and badly maintained central heatings boilers and gas fires

131
Q

explain the danger of carbon monoxide

A

carbon mooxide is a toxic gas which combines with haemoglobin in the blood and reduces the oxygen carrying cpacity leading to death by suffoctaion.

132
Q

how is soot formed?

A

by incomplete combustion of diesel

133
Q

unburned hydrocarbons escape in?

A

exhaust fumes

134
Q

why are they known as a carcinogen?

A

they may contain benzene a known carcinogen

135
Q

why are lead componds added to petrol?

A

to improve engine performance

136
Q

explain why lead is dangerous?

A

lead build up in body tissue and can dammage the nervous system

137
Q

how is the problem reduced?

A

by using unleaded petrol

138
Q

how is carbon dioxide formed?
why is it bad?

A
  • by complete combustion
  • co2 is a greenhouse gas which contributes to global warming
139
Q

explain how photochemical smog is formed?

A

nitrogen dioxide is present in exhaust gases which can react with unburned hydrocarbons in the presence of sunlight. The smog is produced via complex series of reactions involving free radicals

140
Q

explain the harms smog causes?

A

contains chemical irritants (may increase summer increase in asthma attacks

141
Q

how is acid rain formed?

A

by the presence of non-metal oxides in the atmosphere. mainly oxides of nitrogen and sulphur.

When the fraction e.g petrol is burned sulphur reacts with oxygen in the atmosphere to make oxides. Sulphur dioxide causes air pollution. These toxic oxides mix with rain water to make acid rain

142
Q

what is sulphur?

A

an impurity in petroleum fractions

143
Q

what is petroleum and sulphur made up of?

A

petroleum- remains of living organisms
sulphur - is a constituent of a protein

144
Q

how is sulphur dioxide formed?

A

burning of fossil fuels

145
Q

what are the two equations for sulphur dioxide?

A

S + O2 —-> SO2

CH3SH +3O2 —–> CO2 +2H2O +SO2

146
Q

sulphur dioxide causes…?

A

Air pollution

147
Q

sulphur dioxide can be further oxidised to?

A

sulphur trioxide

148
Q
  1. equation for sulphur trioxide
  2. these both (sulphur dioxide + trioxide) are acidic oxides which dissolve to form?
A
  • 2SO2 +02 —->2SO3
  1. SO2 + H20 —> H2SO3 (sulphorous acid)
    SO3 +H2O —-> H2SO4 (sulphuric acid )
149
Q

what cause the most pollution/carbon emissions?

A

coal burning in power stations

150
Q

how is sulphur dioxide produced?

A

burning of fuels in power stations

151
Q

How is sulphur dioxide removed from flue/chimney gases?
how does this work?

A
  • flue-gas desulphurisation
    removed by reacting with an alkali - neutralisation reaction
152
Q

which compound can be used to remove sulphur dioxide?

A

calcium oxide

153
Q

how is calcium oxide obtained?

A

by heating calcium carbonate via thermal decomposition

154
Q

equation for obtaining calcium oxide?

A

CACO3 —–> CAO + CO2

155
Q

why is this a problem?

A

CO2 gas is produced - greenhouse gas

156
Q

calcium oxide removes sulphur dioxide via (equation)
what type of reaction is this?
what does it form?

A
  • CAO +SO2 —–> CASO3
  • NEUTRALISATION REACTION
  • FORMS CALCIUM SULPHITE
157
Q

calcium sulphite is easily…?
what is gypsum used for?

A
  • oxidised to form hydrated calcium sulphate (gypsum) CaSO4.2h2O
  • in the building industry to make plasterboard
158
Q

how else can SO2 be removed?
equation?

A

by using a suspension of limestone (calcium carbonate in water)
CACO3 + SO2 ——> CASO3 + CO2

159
Q

where does nitrogen oxide come from?
what type of reaction is this?

A

the atmosphere is mainly composd of nitrogen =80% , oxygen = 20% combustion

160
Q

how are oxides of nitrogen formed?

A

at very high temperatures which are high enough to overcome the activation energy for reaction between oxygen and nitrigen to form nitrogen dioxide

161
Q

nitrogen of monoxide equation?

A

N2 + O2 —–> 2NO

162
Q

nitrogen dioxide equation?

A

2NO +O2 —–> 2NO2

163
Q

nitrogen dioxide reacts with rainwater + oxygen to form …?
equation?

A

NITRIC ACID ( a major component in acid rain)

4NO2 + O2 + 2H2O——-> 4HNO3

164
Q

What are catalytic converters?

A

Are fitted to exhaust systems of modern cars to remove carbon monoxide nitrogen oxides and unburned hydrocarbons.

165
Q

Converters are usually a mixture of?
What Structure provides a…?

A
  • platinum, palladium, rhodium
  • honeycomb ( of ceramic material) structure provides a large SA this increases the efficiency of the catalyst and reduces the amount of catalyst needed hence the cost
166
Q

The catalytic converters remove up to… of pollutant gases

A

90%

167
Q

Example of converter reactions

A
  1. 2CO + 2NO —> 2CO2 + N2
  2. C8H18 + 25NO —-> 12.5N2 + 9H2O
168
Q

In the catalytic converters:
Carbon monoxide is converted into..?
Oxides of nitrogen is converted to..?
Unburnt hydrocarbons converted to..?

A
  • carbon dioxide
  • nitrogen
  • carbon dioxide and water
169
Q

Explain why this is good?

A

Nitrogen is harmless
Co2 is less dangerous than CO

170
Q

Why do converters only work with unleaded petrol?

A

Lead poisons the catalyst

171
Q

FINISH

A

Chemistry Y12 (11 decks)

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