Alkanes Flashcards
What is petroleum?
Mixture consisting of mainly alkane hydrocarbons that can be separated by fractional distillation
What is the method of fractional distillation?
1) Crude oil vaporised at 350°C
2) Vapourised curde oil passed into fractionating column which has a negative temperature gradient
3) As vapour rises it cools
4) Molecules condense at different temperatres, so drawn off at different levels in the column
What is the residue(1st bottom) fraction? what are the uses?
Fuel oil: Ships and power stations
Wax: Candles and Lubrication
Bitumen: Roofing and road surfacing
What is the fraction that is drawn off at 340°C (2nd)? What are the uses?
Mineral oil: lubrication
What is the fraction that is drawn off at 250°C (3rd)? What are the uses?
Gas oil(diesel): Diesel fuel, Central heating fuel
What is the fraction that is drawn off at 180°C (4th)? What are the uses?
Kerosine(paraffin): Jet fuel, Petrochemicals, central heating fuel
What is the fraction that is drawn off at 110°C (5th)? What are the uses?
Naphtha: processed to make petrochemicals
What is the fraction that is drawn off at 40°C (6th)? What are the uses?
Petrol: cars
What is the top fraction that remains a gas used for?
Liquified petroleum gas, camping gas
What does thermal cracking involve?
- High temperature
- Produces high percentage of alkenes which can be used go make plastics
What does catalytic cracking involve?
- Zeolite catalyst
- Slight pressure and high temperature (significantly less than thermal cracking)
- Mainly produces aromatic hydrocarbons and motor carbons
What does the formation of soot in incomplete combustion lead to?
Can cause breathing problems and build up in engines, damaging them
What does the formation of carbon monoxide in incomplete combustion lead to?
Poisonous as it binds to haemoglobin more readily, and blocks oxygen
What do catalytic converters involve, and what do they do?
Palladium, platinum, or rhodium catalyst that has a honeycomb structure, increasing SA - heterogenous catalyst
Removes unburnt hydrocarbons, oxides of nitrogen, and carbon monoxide from exhausts
What are the conditions needed for oxides of nitrogen to form?
Spark
High temperature
What are the dangers of unburnt hydrocarbons and oxides of nitrogen?
React in presence of sunlight, forming ground level ozone, which causes smog. Irritates eyes, aggravates respiratory problems
What is the danger of SO2
Dissolves in moisture which makes sulfuric acid, causing acid rain. This damages vegetation, corrodes buildings and statues and kills marine wildlife
How can SO2 be removed from flue gases?
Using CaO or CaCO3. Powdered CaO or CaCO3 mixed with water, making an alkaline slurry.
Flue gases mixed with this, acidic sulfur dioxide reacts with them, causing them to form a salt(calcium sulfide)
Stages of chlorination of alkanes
Stage 1: Initiation - UV breaks Cl-Cl bond to make free radicals
Stage 2: Propagation - Cl radical reacts with methane making a methyl radical which attacks a Cl2 molecule forming CH3Cl
Stage 3: Termination - Free radicals join
What happens in Chlorine is in excess?
Cl free radicals attack the chloromethane, producing dichloromethane onwards…
Nucleophiles
Electron pair donors
Nucleophiles that attack halogenolkanes
OH⁻ CN⁻ NH3
Halogenoalkane with hydroxide conditions:
Heat under reflux in aqueous solution
Halogenoalkane with cyanide conditions:
Reflux with ethanolic potassium cyanide
