Topic 7- organic chemistry Flashcards
What is crude oil?
Crude oil is mixture of compounds; a fossil fuel consisting of the remains of ancient biomass
Finite resource
What is a hyrdocarbon
A compound made up exclusively of hydrogen and carbon atoms
What are alkanes?
Saturated hydrocarbons of a general formula: CnH2n+2
What is a homologous series
Series of compounds with same general formula, same functional groups and similar chemical properties
Describe the combustion of hydrocarbons
Exothermic reactions occurring when hydrocarbons are reacted with oxygen
Complete combustion produces CO2 and H2O (carbon and hydrogen atoms are completely oxidised)
Incomplete combustion produces carbon or carbon monoxide and water
Describe the physical properties of alkanes
First few in series and gases, then change to liquid, then to solids
In general, boiling points and viscosity increase as molecules get bigger
Volatility and flammability decrease as molecules get bigger
Poor reactivity
Explain how fractional distillation of crude oil takes place
-Crude oil is heated and vaporised
-Vapour rises up the factorising column
-The column is hotter at the bottom and cooler at the top
-Hydrocarbons cool as they have different boiling points
-Large molecules, low boiling points-collected at the top
-This gives fractions, which can be used in various ways
What is cracking?
When large hydrocarbons are thermally broken down into smaller and useful molecules
What type of reaction is cracking?
Thermal decomposition
What are the conditions for cracking?
Reactant heated to vapour, passed over a hot catalyst (catalytic cracking) or heated to vapour, mixed with steam and heated to high temperatures (steam cracking)
How are the products of cracking used?
The products are alkanes and alkenes- used as polymers and starting materials for synthesis
What is an alkene?
Unsaturated hydrocarbon. Contains a C=C bond.
General formula for alkenes is: CnH2n
What is the test for alkenes?
Add bromine water. Colour change occurs from orange to colourless
Describe the combustion of alkenes
They burn with smoky flames due to incomplete combustion
Describe addition reactions of alkenes
Addition atoms across the C=C so that the double bond becomes a single carbon-carbon bond
a)with hydrogen- hyrdrogenation; requires a higher temperature and a nickel catalyst
b) With steam- hydration; requires high temp, pressure and concentrated phosphoric acid (H3PO4) as a catalyst
c) With BR2/Cl2/Ix- addition of halogens
