Topic 12 - Organics Flashcards
Define hydrocarbon
A compound made up of only C and H atoms
Define crude oil
Mixture of millions of hydrocarbon s
How is crude oil processed?
Through fractional distillation
Describe the fractional distillation of crude oil
1) oil enters the fractionating column, heated until most of it has turned into a gas (bitumen is drained off at the bottom)
2) the column is hotter at the bottom and colder at the top
3) each molecule rises as a gas until it reaches its boiling point, then it condensed into a liquid; longer hydrocarbons have high BPs
4) each different hydrocarbon has a different boiling point - because of this, they all condense at different heights in the column
5) therefore molecules with similar boiling points are separated into the same columns
6) bubble caps in the fractionating column stop the separates liquids from running back down the column and remixing
What is the order of hydrocarbons in terms of boiling points
Refinery gases Gasoline Kerosene Diesel Fuel oil Bitumen
Describe refinery gases
BPs less than 0°C
CH4 -> C4H10
Fuel for home Heating
Describe gasoline
BPs between 0°C and 150°C
C5H12 -> C9H20
Fuel for cars
Describe kerosene
BPs between 150°C and 200°C
C10H22 -> C14H30
Fuel for planes
Describe diesel
BPs between 200°C and 300°C
C15H32 -> C19H40
Fuel for trucks
Describe fuel oil
BPs between 300°C and 400°C
C20H42 ->C29H50
Fuel for ships
Describe bitumen
BPs more than 400°C
C30H62 and up
Used for making roads
Define alkanes
The main type of hydrocarbon found in fuel oil
Describe the general formula for alkanes
CnH2n+2
What is a homologous series?
- same general formula
- similar chemical reactions
- trends in physical properties
What are isomers ?
- same molecular formula
* different structural formula
State the names and formulas of the first 5 alkanes
1) methane (CH4)
2) ethane (C2H6)
3) propane (C3H8)
4) butane (C4H10)
5) pentane (C5H12)
Define saturated
Only containing single bonds
Why is CO toxic
- binds irreversibly to haemoglobin
* reduces the amount of oxygen which can be transported
What is needed for alkane substitution and what does it produce
UV light
Haloalkanes (e.g. bromomethane)
What is needed for catalytic cracking
Powdered aluminium oxide (lowers Ea)
650°C (achieves Ea)
Why is catalytic cracking necessary
Oil supply is mostly long hydrocarbon chains
Oil demand is for shorter hydrocarbon chains
Catalytic cracking shortens alkane chains while also producing useful alkenes
State the general formula of alkenes
CnH2n
What is the functional group of alkenes
C=C
Define unsaturated
Does not only contain single bonds
What is an addition reaction with bromine used for
To tell the difference between alkanes and alkenes
Describe and explain an addition reaction with bromine
1) Add the substance to bromine
2) shake it
3) if it stays the same, the substance is an alkane. If it goes colourless (the bromine has been used up), it is an alkene
4) this is because the bromine atoms add into the molecule where the gaps were, breaking the double bond (because the electrons from bromine repel the shared pair) and forming the haloalkane dibromoethane.
What is needed for addition polymerisation of alkenes?
High temperature (breaking one of the C=C)
High pressure (joining them into a long chain)
Describe polyethene
H H
| |
—(— C - C —)—
| | n
H H
used: bags, drinks bottles
Describe polypropene
H CH3
| |
—(— C - C —)—
| | n
H H
Uses: crates, ropes
Describe polychloroethene
H Cl
| |
—(— C - C —)—
| | n
H H
Uses: guttering, wire insulators
Describe polytetrafluoroethene (PTFE)
F F
| |
—(— C - C —)—
| | n
F F
Uses: non-stick surfaces
Why is it difficult to dispose of addition polymers ?
They are inert (unreactive -> don’t biodegrade) because the carbon-carbon bonds in the polymer chain are very strong and aren’t easily broken
Don’t burn because it can release toxic gases
How can you dispose of addition polymers ?
1) recycle/ reuse
2) landfills
3) incinerate (use the energy released to generate electricity)
What is the problem with incinerating addition polymers
It releases toxic gases:
• hydrogen chloride
• hydrogen cyanide
What is the functional group for alcohols?
O-H
What is the general formula for alcohols?
CnH2n+1OH
What are the two ways of making ethanol?
1) hydration of ethane
2) fermentation of glucose
Describe the hydration of ethene
Addition reaction, reversible
Ethene + water (steam) -> ethanol
Conditions:
• 300°C
• 65atm
• catalyst phosphoric acid (H3PO4)
Pros:
• really fast
• cheap because ethene is cheap and not much is wasted
• makes pure ethanol
Cons:
• high energy cost
• crude oil- raw material - non-renewable, will soon become v expensivo
Describe the fermentation of glucose
Glucose -> 2 ethanol + 2CO2
Conditions:
• yeast (contains enzymes- naturally occurring catalysts)
• 30°C (optimum for yeast enzymes)
• without O2 (otherwise ethanoic acid is formed)
Pros:
• low energy cost
• sugar cane is renewable, as is yeast
Cons:
• makes impure ethanol -> needs to be distilled and purified
• slow
What are the methods of alcohol oxidation?
1) combustion
2) microbial oxidation
3) potassium dichromate (VI) in dilute sulfuric acid : acidified
Describe alcohol combustion
alcohol + oxygen -> CO2 + H20
Burns cleanly: blue, almost invisible flame
Describe microbial oxidation of alcohols
Microbes contain enzymes, use alcohols as an energy source. They use oxygen in the air to oxidise alcohols
Alcohol + 2[o] -> carboxylic acid + water
Describe the reaction between alcohols and acidified potassium dichromate (VI)
Alcohol + 2[o] -> carboxylic acid + water
Colour change: orange -> green
Oxidising agent = dichromate (VI)
How to draw carboxylic acids
Functional group is
C=O
|
O - H
Fill up other C’s with H’s
What happens when a carboxylic acid dissociates
Carboxylic acid loses the H in its functional group which becomes H+, the leftover O becomes O-
The substance “anoate” and is a salt
These salts always have 1- charge
Describe the reaction between alcohols and carboxylic acids
Alcohol + carboxylic acid -> ester + water
How do you draw an Ester?
Lose the H from the functional group of the carboxylic acid, lost the OH functional group of the alcohol
What is the functional group of an Ester?
C=O
|
O
How to make an ester in the lab
1) add a few drops of concentrated sulfuric acid into a boiling tube using a dropping pipette
2) add 10 drops of ethanoic acid
3) add an equal volume of ethanol
4) place the billing tube in a beaker of water and place on a tripod
5) beat using a Bunsen burner until the water starts to boil, then turn off the Bunsen
6) after 1 minute, remove the tube and allow it to cool
7) once cooled, pour the mixture into a test tube of sodium carbonate solution and mix - a layer of ester should form on top of the solution
How to name an Ester:
Take the prefix of the alcohol and add ‘yl’ suffix - this is the first word
The second word is the name of the salt formed
Describe ester properties
- Smell sweet (like pear drops)
- Volatile- evaporate easily
- Used in perfumes
- Used to make food flavourings
What are the ways in which isomers are recognised?
- different shaped carbon chains; straight or branched chains. These isomers have similar chemical properties, but their physical properties (e.g BP) differ
- functional group in different place cause different physical properties
- different functional groups. Could have the same number of carbon, oxygen and hydrogen atoms but have a different functional group- causes very different physical and chemical properties
What is catalytic cracking?
- a form of thermal decomposition
- long-chain alkanes are split into more useful short-chain alkanes and alkenes
- the alkane is heated until it is vaporised, it then breaks down when it comes into contact with the catalyst
How does the combustion of fossil fuels cause acid rain?
1) when fossil fuels are burnt, sulfur dioxide and nitrogen oxides may be produced
2) the sulfur dioxide comes from the sulfur impurities in the hydrocarbon fuels
3) nitrogen oxides are created when the temperature is high enough for the nitrogen and the oxygen in the air to react- this often happens in car engine. Nitrogen oxides include nitrogen monoxide (NO) and nitrogen dioxide (NO2)
4) when sulfur dioxide and nitrogen oxides mix with the water vapour in the clouds they form dilute sulfuric and nitric acid
5) acid rain chases lakes to become acidic- many plants and animals die as a result
Describe butene
- but-1-ene has the C=C connecting the first and second C atoms
- but-2ene has the C=C connecting the second and third C atoms
Describe vinegar
- Ethanoic acid dissolved in water
* Used for flavouring and preserving foods
What are polymers?
Substances of high average relative molecules mass made up by joining lots of monomers (small, repeating units)
The monomers that make up addition polymers have a double covalent bond
What is condensation polymerisation
Reacting two different types of monomer forms bonds between them, making polymer chains
Each monomers has to contain at least 2 functional groups, one on each end of the molecule. Each functional group reacts with the functional group of another monomer, creating long chains of alternating monomers.
For each new bond that forms, a molecule of water is lost
How do polyesters form?
When docarboxylic acid monomers and diol monomers react together, forming an ester link
O O H H || || | | nC — C + n HO-C-C-OH —> || || | | HO OH H H
O O H H
|| || | |
-|—C-C-O-C-C-O—|- n + 2n H2O
| |
H H
Describe polyesters
- some are biodegradable, m own as biopolyesters; they can be broken down by bacteria and other living organisms in the environment over time
- because they can decompose, their pollutant effect is reduced
