Alkanes Alkenes And Halogenalkanes Flashcards
What is a hydrocarbon
A molecule only containing hydrogen and carbon
Saturated meaning
Contains only single bonded atoms eg alkanes
Unsaturated meaning
Contains double or triple bonds eg nitrogen and alkenes
What is a haloalkane
An alkane (only C—C bonds) with one or more halogens bonded to it
Difference between a alkane and alkene
Alkanes have C-C and alkenes have C=C bonds
Functional group of alkane
C—C
Functional group of alkene
C==C
Primary haloalkanes
When the carbon bonded to halogen is only connected to one other alkyl group
Secondary haloalkanes
When the carbon bonded to the halogen is bonded to 2 alkyl groups
Tertiary haloalkanes
When the carbon bonded to the halogen is connected to 3 alkyl groups
nucleophile
Donates an electron pair to form a new covalent bond
What is important for nucleophile substitution
Lone pairs
What is the best nucleophile
Hydroxide ion
What is homolytic fission
The splitting of covalent bonds into radicals where the radicals both take a electron
What process is used to split mixtures with different boiling points
Fractional distillation
What process is used to split the fractions in crude oil
Fractional distillation
What are the 2 types of cracking
Thermal and catalytic
What is required for thermal cracking
700-1200K and pressures up to 7000KPa
One disadvantages of thermal cracking
High cost due to temperature and pressure
What is required for catalytic cracking
Approx 720K,Low pressure (>atmospheric) and a Zeolite catalyst.
What is a zeolite catalyst
Silicon dioxide and aluminium oxide aka aluminosilicates
What structure are zeolite catalysts
Honeycomb for great surface area
What are the main products of catalytic cracking
Branched alkanes,cycloalkanes and aromatic compounds
What needs to happen to the products of catalytic cracking
They need to be fractionally distilled to separate them again
What are the reasons for cracking
It helps fulfil the demand of some of the fractions of crude oil that are in high demand. It also creates feedstock for industry.
Why do some chain lengths of alkanes have greater BP than others
Due to intermolecular forces between molecules (the longer the stronger)
Why do branched alkanes burn better than straight alkanes
Weaker intermolecular forces as they can’t line up directly
Gases Hazardous to humans produced by combustion
Carbon monoxide,carbon dioxide,carbon particulates and unburnt hydrocarbons
Gases that affect the atmosphere produced by combustion
Water (gaseous) and carbon dioxide
Gases that cause acid rain that are produced in combustion
Sulfur dioxide and nitrous oxides (NOx)
Why are unburnt hydrocarbons dangerous
They break down to create photochemical smog and can damage the atmosphere
Main ways of mitigating the damage of the combustion of alkanes
Catalytic converters and flue gas desulfurisation.
How does flue gas desulfuration work
Calcium oxide (aq) is sprayed into the exhaust of powerplants and this reacts with the sulfur dioxide to form gypsum
Gypsum uses
Plaster and plaster boards for construction
How do catalytic converters work
They catalyse the products of internal combustion engines and break down NOx,CO and unburnt hydrocarbons into nitrogen and carbon dioxide (respectfully)
Why are catalytic converters honeycombed shaped
To increase surface area.
What is inside the catalytic converter
A honeycomb of ceramic materials coated with platinum and rhodium metals (rare earth metals)
What is nucleophilic substitution
The process where a halogen is displaced by a negative ion or a molecule with lone pairs
Which bonds are usually broken first
The weakest bond (lowest bond enthalpy)
Electrophile
Accepts an electron pair to form a new covalent bond
