Organic Chemistry Part 2 Flashcards
What is the general formula for alkanes?
CnH2n+2
Are alkanes saturated or unsaturated hydrocarbons?
Saturated
What are the 2 reactions of alkanes? Describe them.
Combustion:
Addition of oxygen
Exothermic
Complete combustion -> CO2 + H2O
Incomplete combustion -> CO + H2O - happens when there is insufficient oxygen
Substitution:
Alkane + Hydrogen -> Haloalkane + HCl/HBr/HI
Conditions: UV light (provides activation energy)
Why is fractional distillation used for crude oil?
Since crude oil is a mixture of different hydrocarbons, fractional distillation is the process used to seperate hydrocarbons according to chain lengths. The shorter the chain, the lower the boiling point, and the higher up it will be collected in the fractionating column.
Describe small hydrocarbons.
Low boiling point
Light in colour
Easy to light
Runny
Describe large hydrocarbons.
High boiling point
Dark in colour
Hard to light
Thick
What are the uses of the fractions in a fractionating column?
To seperate crude oil into:
Refinery gas - Bottled gas for heating and cooking
Gasoline - Fuel in cars (petrol)
Naphtha - For making chemicals
Kerosene/paraffin - Jet fuel
Diesel oil/Gas oil - Diesel engines
Fuel oil - Fuel for ships and home heating systems
Lubricating fraction - Lubricants, waxes and polishes
Bitumen - Making roads
From bottom to top:
Chain length decreases
Higher volatility (greater tendency to form vapour)
Lower boiling points
Lower viscosity (Liquid flows easier)
Describe cracking.
Purpose: Breaking up of long chain alkanes into shorter, more useful chains
Products: Shorter chain alkane + Shorter chain alkane
Conditions:
Temperature = 450 to 800 degrees C
Up to 70 atm
Catalyst: Aluminium Oxide (Al2O3)
What is the general formula of alkenes?
CnH2n
Are alkenes saturated or unsaturated hydrocarbons?
Unsaturated
What are the 4 reactions of alkenes? Describe them.
Combustion:
Complete combustion -> CO2 + H2O
Incomplete combustion -> CO + H2O
Addition reactions:
Hydrogenation (+H2):
Reagents:
Alkene
Hydrogen
Conditions:
150 degrees C
Nickel catalyst
Halogenation (+Br2/F2/Cl2/I2)
Addition of water:
Reagents:
Alkene
Steam
Conditions:
300 degrees C
Acid catalyst
60 atm
Product is always an alcohol
Hydrohalogenation(+HCl/HBr/HI)
Describe a test for saturation.
Add bromine water (Br2)
If alkane -> solution stays orange
If alkene -> Solution turns from orange to colourless
