Alkanes And Alkenes Test Flashcards
What’s a functional group?
An atom or group of atoms that give a molecule its characteristic physical/ chemical properties.
What is a homologous series?
Have the same general formula and same functional group; differ by -CH2- unit.
What’s a formula?
A way of expressing the ratio of elements in a compound
General formula
Algebraic eg CnH2n
Empirical formula
Smallest whole number ratio of elements in a substance
Molecular formula
Actual number of each element in a covalent molecule
Displayed formula
Shows all the bonds
Structural formula
Shows the functional groups
Skeletal formula
Shows only bonds plus non-carbons or hydrogens (Heterolytic-atoms)
Addition reaction
Joining two or more molecules together
Polymerisation reaction
Joining lots of small simple molecules together
Elimination reaction
Small group of atoms break away from a larger molecule
Substitution reaction
One species is replaced by another
Species
Atom, ion or molecule
Hydrolysis reaction
Splitting a molecule into two new molecules using H+ and OH- ions in water
Oxidation reaction
Electrons lost by a species
Reduction reaction
A species gains electrons
Free radical substitution steps
- Initiation - formation of a radical from UV light
- Propagation A and B - using a radical to make a radical
- Termination - two radicals react
Thermal cracking of petroleum (crude oil)
High temperature (up to 1000 deg C)
High pressure (up to 70 atm)
Produces lots of alkenes
Catalytic cracking of petroleum (crude oil)
Zeolite catalyst
Slight pressure
High temperature (up to 450 deg C)
Produces aromatic hydrocarbons and motor fuels
Reforming
Turning straight chain alkanes into branched-chain and aromatic
Reduces knocking
Combustion of alkanes
Into CO2 and H2O
Incomplete combustion of alkanes
Carbon monoxide, water, soot
Combusting fossil fuels
Releases:
Greenhouse gases
Carbon monoxide
Carbon particulates
Sulphur oxides
NOxes
Reducing environmental effects of combusting alkanes
Catalytic converters turn nitrogen monoxide and carbon monoxide into nitrogen and CO2
Alkenes
Unsaturated
Functional group C=C
General formula CnH2n
Why do alkenes have geometrical isomerism (stereoisomerism)?
The molecule cannot rotate around the double bond because this would break the pi bond
Stereoisomerism
ONLY OCCURS when BOTH CARBONS have TWO DIFFERENT substituents attached to them
E (opposite)/ Z (zame zide)
Cis-trans IF both carbons have a hydrogen attached
Naming stereoisomers
Same as normal, number from the double bond, determine isomerism by high priority groups
Electrophilic addition
CURLY ARROWS: DO THEM RIGHT
Major and minor products from different transient intermediates
Transient intermediates
Exist for a short time
Different stabilities- 1, 2, 3, where higher number is more stable due to inductive donating electron effect
Carbocations in electrophilic addition
Disposing of polymers
Landfill: it’s in landfill. We’re running out
Recycle: increases use for carbon footprint. Downcycle
Incinerate: energy. Releases bad stuff
Crack: turn into fuels. Lots of bad waste products, energy intensive
