Organic Chemistry Flashcards
How many bonds can carbon atoms form and why?
It can only form 4 bonds because it has 4 electrons in its outer shell
What is a hydrocarbon?
A compound made up of only hydrogen and carbon
In what ways are a structural formula and a molecular formula different?
A structural formula shows atoms and bonds while a molecular formula shows just atoms
Alkanes are ______ hydrocarbons
Saturated
Alkenes are ______ hydrocarbons
Unsaturated
What are saturated hydrocarbons?
Hydrocarbons with only single bonds between C atoms (alkanes)
What are unsaturated hydrocarbons?
Hydrocarbons with a C=C double bond (alkenes)
What are the general formulae for alkanes and alkenes?
Akanes: Cn H2n+2
Alkenes: Cn H2n
How is crude oil formed?
From remains of marine organisms over millions of years
How are individual hydrocarbons extracted from crude oil?
Fractional distillation
What is the first step in fractional distillation?
Evaporation of crude oil
Why do fractions condense at different points in a fractional distillation column?
Because they have different boiling points. Fractions with a high bp will condense lower in the column (longer chains of C) and fractions with a low bp will condense higher in the column (shorter chains of C)
What happens to the properties of the gases as you rise through a fractional distillation column?
Burn easier - better fuels
Chain length decreases
Bpt decreases
Lighter colour
What properties do larger molecules have? (FD)
High boiling point
Not very volatile
Do not flow easily
Do not ignite easily
What properties do smaller molecules have? (FD)
Low boiling point
Very volatile
Flow easily
Ignite easily
What does volatility mean?
How readily a substance vapourises (goes from a liquid to a gas)
Which length chains are the most commercially valuable?
Short chains because they are the best fuels
How can you solve the problem of oversupply of long chain saturated hydrocarbons after fractional distillation?
Cracking
What is cracking?
The breaking down of long chain saturated hydrocarbons (alkanes) using heat and a catalyst
What does cracking produce?
Shorter chain alkanes (better fuels) and alkanes which can be used to make plastics
What will a combustion reaction with an alkane/alkene always produce?
Carbon dioxide and water
What does hydrogen produce when it burns?
Water
2H2+O2->2H2O
What can hydrogen be used for?
As rocket fuel and increasingly to power cars
What are the advantages of using hydrogen as a fuel?
It’s renewable because it’s produced from water
Water is the only product made when it burns so it doesn’t contribute to global warming
There’s lots of it about because there’s a lot of water in the environment
What are the disadvantages of using hydrogen as a fuel?
Large amounts of electricity are needed to produce hydrogen by electrolysis
Storage of fuel in the car is in heavy, pressurised containers
Forms an explosive mixture with air
Why is using hydrogen as a fuel not completely carbon-neutral?
It takes a lot of electricity to carry out electrolysis to separate hydrogen from water
How could we make hydrogen a carbon neutral fuel?
Generate energy for electrolysis through renewable sources e.g. wind or solar
What is the fire triangle?
The 3 things needed to start and maintain a fire
How can we apply the fire triangle to fire fighting methods?
Removing one of the 3 essential things that keep a fire burning
e.g. Add water -> Removes heat
Fire blanket -> Removes oxygen
Create fire break -> Removes fuel
What are isomers?
Molecules with the same molecular formula but a different structural formula
How do we name isomers?
Based on how many carbon atoms can be in a line
e.g. Butane has the same number of carbon atoms as methylpropane
In what case do we use the preposition methyl-?
When there is one side-chain of carbon stemming from the longest chain
e.g. Methylpropane
(isomer of butane)
In what case do we use the preposition dimethyl-?
When there are two side-chains of carbon in opposite directions from the longest possible chain
In what case do we use the preposition ethyl-?
When there is a side chain consisting of two carbon atoms stemming from the largest possible line of carbon atoms
How can you create a different isomer in an alkene without creating a side-chain?
By moving the position of the double bond
We show this by placing a number in the middle of the name
e.g. But-1-ene or But-2-ene
How would you go about drawing an isomer from a name?
Start from the back of the name, create the carbon skeleton and work backwards through the name
