Organic Chemistry Flashcards
What is crude oil?
Crude oil is a mixture of compounds; a fossil fuel consisting of the remains of ancient biomass.
Finite resource - cannot be replaced as it is used up
What is a hydrocarbon?
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 reaction occurring when hydrocarbons are reacted with oxygen.
- Complete combustion produces carbon dioxide and water
- Incomplete combustion produces carbon or carbon monoxide and water
Describe the physical properties of alkanes
- First few in series are gases, then change to solids, 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 fractionating column
- The column is hotter at the bottom and cooler at the top
- Hydrocarbons cool as they go up the column and condense at different heights, as they have different boiling points
- Large molecules, high boiling points - collected at the bottom
- Small molecules, low boiling points - collected at the top
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 or heated to vapour, mixed with steam and heated to high temperatures
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 carbon-carbon double bond so that the double bond becomes a single carbon-carbon bond
a) with hydrogen - requires a high temp and a nickel catalyst
b) with steam - requires a high temp and concentrated phosphoric acid as a catalyst
c) with Br2/Cl2/I2 - addition of halogens
State characteristics of methanol, ethanol, propanol and butanol
- Dissolve in water to form a neutral solution
- React with sodium to form hydrogen
- Burn in oxygen
- React with carboxylic acids in presence of acid catalyst to form esters
What are some uses of alcohols?
- Fuels
- Solvents
- Drinks
State the conditions required for fermentation of glucose and state the equation of the reaction
30 degrees Celsius, aqueous solution of the glucose, absence of air, yeast added:
C6H12O6 –> 2CH3CH2OH + 2CO2
What is a polymer? How do molecules containing C=C bond form polymers?
A polymer is a long chain molecule which is made by lots of smaller molecules joining together
C=C bonds open up and many smaller molecules join together to form a chain. No other products are made
It is called an addition polymerisation reaction
Give 3 examples of addition polymers and their uses
Polyethene - plastic bags
polytetraflouroethene - non-stick kitchenware
Polychloroethene - water pipes
