Organic Chemistry Flashcards
Crude oil
A mixture of different hydrocarbons
Formed from the remains of plankton that died millions of years ago and got buried in mud
Uses of crude oil
Plastic
Petrol
Pharmaceuticals
Cosmetics
Hydrocarbon
Made of hydrogen and carbon atoms
Alkane
A type of hydrocarbon
Carbon surrounded by hydrogen with single bonds
General formula for alkanes
Cn H2n+2
Why are alkanes saturated molecules?
Because carbon can only have 4 bonds
And in alkanes they are fully bonded with single molecules showing they have the maximum number of hydrogens possible
Viscosity
Thickness of a fluid
High viscosity = thick and doesn’t flow easily
Low viscosity = think and flows easily
Properties of long chain hydrocarbons
Viscos/ think (flows slowly)
Less flammable
High boiling point (requires more energy to overcome bonds)
Properties of short chain hydrocarbons
Not viscos (Thin) flows easily
Flammable
Low boiling point (not much energy required to break bonds)
How does properties of hydrocarbons change?
When written all down, they change proportionally going up or down
Eg going up they increase in viscosity
How are hydrocarbons used for fuels?
Alkanes are combusted ie burnt
What does complete combustion of alkanes release?
Carbon dioxide and water
Fractional distillation
Separating crude oil into ‘fractions’ in a column
Depending in their chain length eg long chain or shirt chain thus their properties
Done so we can use the different hydrocarbon lengths for different purposes
How does fractional distillation work?
Crude oil heated and becomes a gas
Enters the column, where it’s hot at the bottom and cool at the top
As the gas rises up the column, different hydrocarbons will reach their boiling point at different points
The long ones reach it at the hot bottom so they condense there and leave
Short ones condense into liquid at the top and leave
Very short ones remain as gases and leave
Long chain hydrocarbon uses
Fuel for ships and power stations
Bitumen/ asphalt for roads
Diesel
Short chain hydrocarbon uses
Fuel for aircraft
Petrol
Fuel for house cooking
Cracking
Process of breaking long chain hydrocarbons to be shorter
As shorter ones are more flammable and easier use for fuel
This does not involve crude oil. ONLY HYDROCARBONS
What are the products of cracking?
A short chain alkane and an alkene
Conditions for catalytic cracking
Very high temperature
Catalyst to speed it up
Steam cracking conditions
Very high temp
Steam
Alkene
Type of hydrocarbon with 1 double covalent bond between 2 carbon atoms
Alkene general formula
Cn H2n
Are alkenes saturated?
No.
Because they have 2 less hydrogen molecules than the corresponding alkane they possibly can have
Does methene exist?
No because there must be a double bond between 2 carbon atoms
But meth- only has 1 carbon atom so it’s not possible
Use of alkenes
Making polymers
As a starting material for other chemicals
More reactive than corresponding alkane
How to test for alkenes?
Add orange bromine water to it
Shake, if it’s an Alkene it goes from
Orange to colourless
NOTTTTT CLEARRRRRRR
What happens when alkenes are combusted?
They burn in air with a smoky flame
Produces carbon dioxide and water just like with alkane
Also produces unburnt carbon atoms due to incomplete combustion
Hydrogenation
Using hydrogen in order to turn an alkane into its corresponding Alkene