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ORGANIC Flashcards

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1
Q

What is a homologous series?

A

A series of molecules that show a gradual trend in physical properties, can be represented by a general formula and have the same functional group. Each successive member of the series differs by a CH2 group

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2
Q

Alkanes are saturated or unsaturated?

A

saturated

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3
Q

What is an isomer?

What are the 3 types?

A

Molecules with the same molecular formula but different structural formulae.

3 types:
Chain
Position
Functional

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4
Q

What is fractional distillation?

A

The continued evaporation and condensation of a reaction causing it separate due to differences in boiling points.

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5
Q

What is petroleum?

A

A complex mixture containing mainly alkane hydrocarbons that can be separated using fractional distillation.

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6
Q

Why do people using cracking?

A

To break up the less valuable (less in demand), longer chain hydrocarbons that are less flammable, into shorter chain alkanes and alkenes

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7
Q

What are the two types of cracking called?

A

Thermal and Catalytic

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8
Q

Describe thermal cracking and its benefits

A

High temp (up to 1000 degrees)

High pressure (up to 70 atm)

Produces lots of alkenes which can be used to make valuable polymers eg. poly(ethene)

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9
Q

Describe catalytic cracking and its benefits

A

Uses a zeolite catalyst at a slight pressure and high temp (450)

Mostly produces aromatic hydrocarbons and motor fuels

Using a catalyst cuts costs as it can be done at a lower pressure and temperature and it also speeds up the reaction which saves time.

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10
Q

Alkanes are useful for?

A

Fuels

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11
Q

Complete combustion of alkanes produces?

A

CO2 and H2O

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12
Q

What is produced/ can be produced in incomplete combustion?

A

Carbon Monoxide

Carbon dioxide

Carbon

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13
Q

How are oxides of nitrogen formed in the internal combustion engine?

Why is it bad?

A

High temperature and pressure inside car engines cause nitrogen and oxygen atoms in the air to react together.

Acid rain

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14
Q

How is the pollutant carbon formed in the internal combustion engine?

Why is it bad?

A

Incomplete combustion of hydrocarbons

Breathing problems and can also build up causing engine problems

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15
Q

How is the pollutant carbon monoxide formed in the internal combustion engine?

Why is it bad?

A

Incomplete combustion of hydrocarbons

Toxic to humans - limits RBCs capacity to carry oxgen

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16
Q

What is the issue with unburn hydrocarbons as a result of internal combustion engines?

A

React in the presence of sunlight to form ground level ozone (O3).

This irritates peoples eyes and is very bad for the respiratory system

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17
Q

How can (which) emissions be reduced using catalytic converters?

A

They reduce the output of carbon monoxide, nitrogen oxide and unburnt hydrocarbons.

Honeycomb shape (large surface area) made of ceramic material coated in platinum and rhodium (catalysts).

As the gases pass over this they react forming less harmful products. eg. co2 and nitrogen

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18
Q

How can we limit sulfur dioxide reaching the atmosphere in flue gases?

A

Calcium carbonate or calcium oxide is mixed with water to form an alkaline slurry.

The flue gases mix with the slurry and the acidic sulfur dioxide reacts with calcium compounds to form harmless salts.

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19
Q

Why is the ozone layer important?

A

Absorbs UV radiation which could be potentially harmful.

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20
Q

What are CFCs?

A

Chlorofluoroalkanes where all the hydrogens have been replaced by chlorine and fluorine atoms.

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21
Q

Why are CFCs bad?

A

Create holes in the ozone layer

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22
Q

How do CFCs create holes in the ozone layer?

A

Chlorine free radicals are forming in the ozone layer when C-Cl bonds are broken by UV radiation.

These free radicals are catalysts.

They attack the ozone in the atmosphere and regenerate more Cl free radicals.

It breaks down ozone into oxygen

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23
Q

What are the 2 equations and overall equation that show the decomposition of the ozone layer?

A
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24
Q

What is a nucleophile?

A

An electron pair doner?

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25
Conditions for nucleophilic substitution of OH- CN-
Reflux reaction. Alkane dissolved in ethanol Aqueous sodium cyanide/hydroxide
26
Nucleophillic substitution using ammonia conditions?
Sealed container under pressure Dissolve bromoethane in ethanol Add concentrated NH3
27
Why do iodoalkanes react faster than fluoroalkanes?
As the C-I bond is shorter than C-F and therefore takes less energy to break. Bond needs to break for the reaction to occur
28
What is a free radical?
A particle with an unpaired electron
29
What are the conditions for elimination reactions?
Alkaline and under reflux - dissolved in ethanol
30
Which solutions favour elimination and which conditions favour substitution?
Ethanolic solutions favour elimination Aqueous solutions favour substitution
31
What is a chain isomer?
Different structural arrangement of atoms can be straight chain or branched but have the same molecular formula. eg. Butane and 2-methylpropane
32
What is a position isomer?
These have the functional group of the molecule in different positions on the carbon chain.
33
What is a functional group isomer?
Same molecular formula but different functional groups
34
What is a stereoisomer?
Same structural formula but different spatial arrangement.
35
Why is ozone important?
It absorbs lots of UV radiation which is important for protecting us from its dangers such as cancer.
36
Overall ozone depletion equation?
2O3 -> 3O2
37
Why do halogenoalkanes contain polar bonds?
The halogen atom is more electronegative than the carbon atom so the electron density is drawn towards the halogen atoms. This creates regions of delta - and delta +
38
What are nucleophiles? Examples
Electron pair donor and they are attracted to areas with positive charge. :CN - :NH3 :OH-
39
Required conditions for nucleophilic substitution with a hydroxide nucleophile?
Warm aqueous potassium or sodium hydroxide. Heat with halogenoalkane under reflux
40
Required conditions for nucleophilic substitution with a cyanide nucleophile?
Heat halogenoalkane with ethanolic potassium cyanide under reflux.
41
Required conditions for nucleophilic substitution is an ammonia nitrile nucleophile?
Sealed container under pressure Dissolve halogenoalkane in a small volume of ethanol and add concentrated NH3. NH3 is concentrated and added in excess to reduce the likelihood of the product reacting with the halogenoalkane.
42
What determines the reactivity of halogenoalkanes?
The carbon halogen bond strength as for any reaction to occur it needs to break. C-F bond is strongest as it has the highest bond enthalpy. So fluoroalkanes react the slowest. C-I bond is the weakest as it has the lowest bond enthalpy and therefore iodoalkanes react the quickest.
43
What determines whether an :OH- undergoes nucleophilic substitution or elimination?
OH- dissolved in water and heater under reflux leads to substitution. OH- in hot ethanolic conditions leads to elimination.
44
C=C has a high ....
electron density
45
What are electrophiles?
Electron pair acceptors. They are attracted to areas with high electron density
46
Why does electrophilic addition occur?
Because C=C has a high electron density so is easily attacked by electrophiles.
47
How to test for alkenes?
Shake alkene in test tube with orange bromine water. Solution quickly decolourises as dibromoalkane is formed
48
What is an addition polymer?
A long chain molecule produce when many alkene or substituted alkene monomers join together.
49
What are PVCs? Uses and modifications?
Poly(chloroethenes) - Long closely packed polymer chains which makes it hard and brittle. Rigid PVC used to make drainpipes and window frames. Plasiticers can be added to PVCs which pushes the polymer chains apart and this weakens the IMFs so they can slide around and bend. Plasticised PVC is more flexible so is used to make electrical cable insulation and clothing.
50
Are polyalkenes biodegradable? Why?
NO Its a long chain, saturated alkane molecule with strong non polar C-C and C-H so they are very unreactive. Not attacked by biological agents like enzymes so are not biodegradable.
51
Do branched polyalkenes have a higher or lower boiling point than straight chains?
Lower As the branches mean the chains are further away so have weaker VDW forces between chains. Meaning long straight chains are often stronger and rigid Short, branched chains are often weaker and more flexible.
52
General formula of alcohols
CnH2n+1OH
53
Why do alcohols have higher boiling points than alkanes of a similar Mr?
Due to the hydrogen bonding that occurs between molecules.
54
Are alcohols soluble in water?
Yes in short chain ones as the -OH group which is polar predominates No in long chain ones as the nonpolar hydrocarbon chain predominates over the -OH group.
55
How are alcohols produced?
Hydration of alkenes Fermentation
56
How does the hydration of alkenes lead to production of alcohols?
Ethene is reacted with steam in the presence of a phosphoric acid catalyst. This is a fast, continuous reaction that produces pure ethanol.
57
How is ethanol produced by fermentation?
Fermentation of glucose: C6H12O6 -> 2C2H5OH + 2CO2 Air is kept out the reaction vesicle to prevent oxidation of ethanol to ethanoic acid. Requires yeast enzymes at 30-40 degrees Ethanol then needs to be separated by fractional distillation. This is slow and a batch process
58
What is a biofuel?
A fuel made from biological material that has recently died.
59
How can ethanol be made as a biofuel?
Sugars from sugar cane are fermented to produce ethanol. The ethanol is then added to petrol.
60
Advantages of using biofuels?
Renewable energy source Carbon neutral
61
Is bioethanol carbon neutral?
YES but not quite: **Plants take in CO2 for photosynthesis:** 6CO2 + 6H20 -> C6H12O6 + 6O2 **Glucose is then fermented to form ethanol:** C6H12O6 -> 2C2H5OH + 2CO2 **Ethanol is burned which then releases CO2:** 2C2H5OH + 6O2 -> 4CO2 + 6H2O These equations show exactly 6 moles of CO2 on both sides of the equation. So its carbon neutral. However, more CO2 is given out in growing, making fertilisers and transport etc....
62
Define carbon neutral?
Process that leads to no net increase of CO2 into the atmosphere
63
Primary alcohols are oxidised to form?
Aldehydes and then carboxylic acids
64
Secondary alcohols are oxidised to form?
Ketones
65
Tertiary alcohols are oxidised to form?
Are not oxidised
66
How can you change how far primary alcohols are oxidised?
**Aldehyde:** - Heat ethanol with potassium dichromate VI and dilute sulfuric acid in pear shaped flask. The aldehyde boils off at a lower temperature so vapour rises and then is condensed. The aldehyde runs down the condenser and is collected in a beaker in **ice** to prevent it evaporating out. **Carboxylic acid** - Heat ethanol with more potassium dichromate VI and concentrated sulfuric acid. Mixture heated using reflux apparatus so the vapour condenses and then drips back into the flask to be boiled again. Eventually, you can distill off the ethanoic acid to collect it.
67
Test for carboxylic acid?
Add sodium carbonate Effervescence
68
Test for haloalkane?
warm aqueous sodium hydroxide and acidify with dilute nitric acid. Add silver nitrate - ppt of halide form-AgX
69
Fehling's Solution to test for?
Add to solution and heat Aldehyde = blue to brick red Ketone = no change
70

A Level Chemistry (12 decks)

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