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Chemistry > 3.3 Organic chemistry > Flashcards

3.3 Organic chemistry Flashcards

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1
Q

Alkanes are saturated hydrocarbons, what does this mean?

A

The only have single C-C bonds.

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2
Q

What is petroleum?

A

A mixture consisting mainly of alkane hydrocarbons that can be separated by fractional distillation.

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3
Q

What is cracking in terms of bonds?

A

Breaking C-C bonds in alkanes.

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4
Q

What are the conditions and products of thermal cracking?

A

Conditions: high pressure, high temperature
Products: high percentage of alkenes

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5
Q

What are the conditions and products of catalytic cracking?

A

Conditions: slight pressure, high temperature, zeolite catalyst
Products: motor fuels, branched alkanes, cycloalkanes

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6
Q

What are the benefits of catalytic cracking?

A

It saves time and money, as the catalyst speeds up the reaction and a lower temperature and pressure is needed.

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7
Q

What are the economic reasons for cracking alkanes?

A

There is a larger demand for lighter fractions like, naphtha and petrol. However, heavier fractions fractions like bitumen aren’t in high demand. So, lighter fractions are much more valuable. Alkenes may also be formed which are useful premediates.

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8
Q

What are alkanes mainly used for?

A

Fuels

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9
Q

What are the 2 types of combustion?

A

Complete
Incomplete, occurs when there is a lack of oxygen, creates CO instead.

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10
Q

What pollutants are created in an internal combustion engine?

A

Oxides of nitrogen
Carbon monoxide
Carbon dioxide
Unburnt hydrocarbons
Sulfur dioxide

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11
Q

How are the gaseous pollutants from internal combustion engines removed?

A

Catalytic converters

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12
Q

What happens when you combust hydrocarbons that contain sulfur?

A

It creates sulfur dioxide which leads to air pollution.

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13
Q

What are the effects of sulfur dioxide on the environment?

A

Erosion of buildings
Killing of plants and trees
Contamination of lakes

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14
Q

How do we remove sulfur from fuel?

A

Flue gas desulfurisation

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15
Q

Describe the process of flue gas desulfurisation.

A

Calcium oxide/ calcium carbonate is coated on a mesh to increase surface area to react forming CaSO3 ( and CO2 for calcium carbonate.) The calcium sulphite is further oxidised to SO4 to make plaster and plasterboard.

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16
Q

What are the environmental effects of oxides of nitrogen?

A

Acid rain which causes:
Erosion of buildings
Killing of plants and trees
Contamination of lakes

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17
Q

What does a catalytic converter do?

A

It reacts NO, CO and unburnt fuel to produce H2O, CO2 and N.
It has a honeycomb structure for increased surface area.
It uses a platinum catalyst

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18
Q

What is the process used to make chloroalkanes?

A

Free radical substitution

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19
Q

What are the 3 stages of free radical substitution?

A

Initiation
Propagation
Termination

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20
Q

What are the conditions for the free radical substitution of chlorine and methane?

A

UV light
Excess methane to reduce further substitution

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21
Q

What is initiation?

A

UV light is used to make a free radical.

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22
Q

What happens in propagation?

A

A free radical is used to make another free radical.

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23
Q

What is termination?

A

2 free radicals react together and stop the reaction.

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24
Q

What is a free radical?

A

A species with an unpaired electron.

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25
Q

Why is free radical substitution a bad method for making chloroalkanes?

A

Polysubstitution reactions occur
Unwanted termination reactions occur
Lots of unwanted products and a poor atom economy

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26
Q

Why can crude oil have a different composition?

A

If it comes from a different source.

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27
Q

Why can crude oil sometimes contain sulfur?

A

Small amounts of other compounds from elements in original plants.

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28
Q

What is fractional distillation (crude oil)?

A

Heating the crude oil and collecting the fractions that boil over a range of temperatures.

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29
Q

What is a fraction?

A

A section of the crude oil containing hydrocarbons with similar chain lengths and properties.

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30
Q

Describe the process of fractional distillation.

A

-Heat the crude oil in a furnace.
-Liquid and vapour pass into the column which is cooler at the top.
-Vapour passes up the tower via trays containing bubble caps until they arrive at a tray that is cool enough, and they condense.
-The mixture of liquids on each tray is piped off.
-Shorter chain hydrocarbons condense in the trays towards the top as they have lower boiling points.
The thick residue at the bottom (tar/ bitumen,) is used for road surfacing . There’s not very high demand. So, it’s cracked.

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31
Q

What are the different fractions?

A

(C1-C3) gases- fuel onsite
(C4-C12) gasoline/petrol- cars
(C12-C16) kerosene/ paraffin- jet fuelling, lighting
(C15-C18) diesel oil- lorries, taxis
(C19-C35) lubricating oil/ waxes- candles, engine oil
(C35-C70) fuel oil- ships, power stations
(C70 up) tar/bitumen- roads, roofing

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32
Q

Why does thermal cracking produce alkenes?

A

When C-C bonds break, one electron from the pair goes to each carbon atom, leaving unpaired electrons so, carbon free radicals. One chain must have a carbon double bond as there aren’t enough hydrogens. To avoid decomposition into hydrogen, alkanes are taken out quickly

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33
Q

What is an aldehyde?

A

Carbonyl group in terminal carbon atoms
Suffix -al

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34
Q

What is a ketone?

A

Carbonyl group (C—O) not attached to terminal carbon atoms.
Suffix -one

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35
Q

Why are CFCs harmful to the environment?

A

The CI-C bonds can be broken through absorbance of uv radiation. This leads to the formation of chlorine atoms (which are free radicals.) which catalyse the decomposition of ozone and contribute to holes in the ozone layer.

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36
Q

What are CFCs and what are they used for?

A

Chlorofluorocarbons, used to cool air inside refrigerators. But, long chain ones are used as dry-cleaning and degreasing solvents.

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37
Q

What is ozone?

A

O3, formed naturally in the upper atmosphere.

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38
Q

What is the ozone layer?

A

A layer of the stratosphere. 15-30km above earths surface. It absorbs UV radiation from the sun.

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39
Q

How was a solution for CFCs created?

A

The results of research of different groups in the scientific community lead to evidence for the legislation to ban the use of CFCs as solvents of refrigerants. Chemists have now developed alternative chlorine-free alternatives.

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40
Q

What type of bonds do halogenoalkanes have?

A

Polar bonds

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41
Q

Which nucleophiles undergo substitution with halogenoalknes?

A

OH-
CN-
NH3

42
Q

What are the properties of halogenoalkanes?

A

Not soluble in water as the bond isn’t polar enough.
Contain permanent dipole-dipole forces and Van der Waals forces.
They mix with hydrocarbons so they can be used as dry-cleaning fluids and to remove oily stains.

43
Q

Why are halogenoalkanes attacked by nucleophiles?

A

Due to polarity, the carbon atom attached to the halogen is electron deficient, so, it can be attacked by electron rich things.

44
Q

What are nucleophiles?

A

Electron pair donor- contain a lone pair of electrons which can be used to form a covalent bond.

45
Q

What are the reaction conditions for nucleophilic substitution with OH-?

A

Warm the mixture
Aqueous alcoholic solution

46
Q

What are the conditions for nucleophilic substitution with CN-?

A

Warm with aqueous alcoholic solution of potassium cyanide.

47
Q

What are the reaction conditions for nucleophilic substitution with NH3?

A

Excess concentrated solution of ammonia in ethanol
Pressure

48
Q

What is the role of OH- in elimination?

A

Instead of acting like a nucleophile, it acts as a base. It removes a H+ ion from the haloalkane.

49
Q

What are the products of elimination?

A

Alkene
Water
Salt

50
Q

What is the functional group of an amine?

A

NH2

51
Q

What are the reaction conditions for elimination?

A

Heat
No water
Dissolved in ethanol

52
Q

What is a structural isomer?

A

It has the same molecular formula but a different structure.

53
Q

What is the functional isomer of an alkene?

A

Cycloalkanes

54
Q

What are the 3 types of structural isomer?

A

Chain
Positional
Functional

55
Q

What is the difference between different isomers?

A

Have different melting and boiling points (molecules with no branching tend to have higher boiling points due to their higher surface area leading to stronger VanderWaals forces.)

56
Q

What is stereoisomerism?

A

Molecules with the some structural formula but with atoms arranged differently in space.

57
Q

What is E-Z isomerism?

A

A form of stereoisomerism and occurs as a result of restricted rotation about the planar carbon-carbon double bond.

58
Q

What is an electrophile?

A

An electron pair acceptor.

59
Q

What are some examples of electrophiles?

A

Hydrogen halides
Halogens
Concentrated sulfuric acid

60
Q

What is the test for alkene?

A

It turns bromine water colourless.

61
Q

Why is there a major and minor product produces in electrophilic addition?

A

Positive inductive effect. The carbon on the double bond with the most R groups attached is more likely to have the positive charge of the carbocation.Because, surrounding carbons push electrons towards it as alkyl groups have larger electron density than H. So, tertiary carbocation intermediates are more stable.

62
Q

What are addition polymers formed from?

A

Alkenes
Substituted alkenes

63
Q

What are the properties of polymers?

A

Unreactive- contain strong bonds, that are non-polar and saturated. (Can lead to disposability problems.)
Produce toxic gases when burnt.
High mpts and bpts- strong VderW forces between chains.

64
Q

What are the benefits of recycling polymers?

A

It reduces the consumption of finite oil resources.
Gets rid of plastics in landfill. (Reducing carbon footprint, energy consumption and water consumption.)

65
Q

What are the energy costs of recycling plastics?

A

Transport of materials
Sorting, melting and shredding
Transport of new products

66
Q

What is a plasticiser?

A

It makes a polymers more flexible. ( gets in between chains and pushes them apart reducing the strength of IMFs. So, they can slide around more and are easier to bend.)

67
Q

What is PVC?

A

It contains long closely packed polymer chains.
Hard and Brittle at room temperature.

68
Q

What is rigid PVC used for?

A

Drainpipes
Window frames

69
Q

What is plasticised PVC used for?

A

It flexible so, it’s used for:
Electric cable insulation
Flooring tiles
Clothing

70
Q

What is an alkene?

A

An unsaturated hydrocarbon.

71
Q

Describe the bonding in an alkene.

A

They contain a double covalent bond, which is a centre of high electron density.

72
Q

How are alcohols produces industrially?

A

Hydration of alkenes in the presence of an acid catalyst.

73
Q

What are the reaction conditions for the hydration of an alkene?

A

Steam
300 degrees
60atm
Solid phosphoric acid catalyst.

74
Q

How is ethanol produced industrially?

A

Fermentation of glucose

75
Q

What are the reaction conditions for fermentation of glucose?

A

Anaerobic
30-40 degrees
Aqueous
Yeast

76
Q

What happens to ethanol made from fermentation?

A

It’s separated from the mixture using fractional distillation and then used as a biofuel.

77
Q

What is a biofuel?

A

A fuel that is made from biological material that’s recently died.

78
Q

Why do we use a temperature of 30-40 degrees for fermentation?

A

A high temperature would cause the enzyme to denature. A low temperature would slow down rate of reaction and yield.

79
Q

Why is the statement the ethanol from fermentation is a carbon neutral fuel invalid?

A

Fossil fuels need to be burnt to power machinery to:
Fertilise the crops
Harvest
Refine
Transport
Burning fuel to power machinery produces carbon dioxide.

80
Q

What are the ethical and environmental issues with using biofuels?

A

Car engines may have to be modified to deal with high ethanol concentration.
The land can’t be used to grow food so, you may not be able to feed everyone in the country.
It’s not entirely carbon neutral.
VOCs are given off during the drying process.

81
Q

What are the different classifications of alcohols?

A

Primary
Secondary
Tertiary

82
Q

What can primary alcohols be oxidised to?

A

Aldehydes and then carboxylic acids

83
Q

What are secondary alcohols oxidised to?

A

Ketones

84
Q

What are tertiary alcohols oxidised to?

A

They are not easily oxidised.

85
Q

What is a suitable mildly oxidising agent for the oxidation of alcohols?

A

Acidified potassium dichromate

86
Q

What are the reaction conditions for the oxidation of an alcohol?

A

Reflux
Dilute H2SO4
(Acidified potassium dichromate)

87
Q

What are the advantages of biofuels?

A

Alcohols burn cleaner than petrol, reducing pollution.
By-products are used as animal feed.

88
Q

What are the advantages of fermentation?

A

Low tech
Cheap equipment
Renewable recourses
Low energy

89
Q

What are the disadvantages of fermentation?

A

Slow
Impure ethanol
Batch process

90
Q

How are alkenes formed from alcohols?

A

Acid-catalysed elimination reactions

91
Q

What are alkenes produced from elimination of alcohols used for?

A

To produce addition polymers without using monomers from crude oil.

92
Q

What are the disadvantages of producing alkenes from elimination?

A

The product isn’t pure. It’s in a solution of water.

93
Q

Why are reflux conditions used?

A

It allows the reaction to occur at a high temperature without losing volatile reactants or products to evaporation. Leading to a higher percentage yield and a more complete reaction.

94
Q

Why do you get a mixture of products when dehydrating alcohols?

A

The carbon-carbon double bond can form on either side of the C with the OH group attached.

95
Q

What are the 3 ways of identifying organic molecules?

A

Melting and boiling point- but many have similar ones.
Spectroscopy analysis- mass spectra, MIR, IR
Identification tests

96
Q

Which test is Tollen’s reagent used for?

A

Aldehydes
Warm tollen’s reagent
Result: silver mirror

97
Q

Which test is Fehlings solution used for?

A

Aldehydes
Warm the solution
Result: blue solution - brick red precipitate

98
Q

What test is used for primary and secondary alcohols and aldehydes?

A

Warm with potassium dichromate and dilute sulfuric acid
Result: orange solution - green solution

99
Q

What test is used for carboxylic acids?

A

Add sodium carbonate or sodium hydrogen carbonate.
Result: effervescence

100
Q

What happens when sulfuric acid reacts with an alkene?

A

Alkenes will react with cold concentrated sulfuric acid to form alkyl hydrogen sulfates. You can then convert the alkyl hydrogen sulfates formed into alcohols by adding water and warming the reaction mixture. If you then add cold water and warm the product, it hydrolyses to form an alcohol. The sulfuric acid isn’t used up — it acts as a catalyst.

101
Q

Anti-bumping granules are placed in the flask when refluxing.
Suggest why these granules prevent bumping.

A

form smaller bubbles or prevent large bubbles

102
Q

Describe the method, including apparatus and practical details, that the student should use to prepare a standard solution.

A

Weigh the weighing boat containing the solid on a balance
Transfer to beaker and reweigh the weighing boat
Record the difference in mass
Add distilled/ deionised water
Stir (with a glass rod) or swirl
Until all solid has dissolved
Transfer to volumetric flask
With washings
Make up to 250cm mark with water
Invert multiple times

Chemistry (14 decks)

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