Alkenes Flashcards
What are alkenes
Unsaturated hydrocarbons with a double chain
Why can’t the alkenes double bond can’t rotate
As they contain a pi bond as they have overlapping orbitals
What types of isomers can alkenes form
Positional
Geometrical
What are postional isomers
This is when alkenes double bonds are in another position
What is geometrical isomerism
When the bonds are arranged differently around the c=c double bond
Z isomerism- same side
E isomerism -either side
What type of reactions do alkenes undergo
Electrophilic addition
What are electrophiles
They are electron deficient atoms that attack double bonds
In electrophilic addition of alkenes if two or more products can be formed which one will be formed and give the order
The most stable carbocation will be formed it’s know as positive inductive effect
Tertiary
Secondary
Primary
How can we test for a double bond
By addition of bromine water which it will be decolourised
What is meant by addition
A reaction that converse a double bond into a single bond
How can plasticisers modify polymer properties
They force polymer chains apart meaning they can slide over each other ie pvc
Why are polyalkenes unreactive and why is this a problem
They have strong polar c-c and c-h bonds and it means they are hard to dispose of
How is l density polyethene made
By being polymerised at high temperatures and pressures and branched polymers are produced
What are the properties of Low density polyethene
Low density
Flexible
Stretch well
Branches chains don’t
What is low density polyethene used for
Plastic bags sheeting insulation cable
How is high density poly ethene made
At low temperatures and pressures with a Ziegler netta catalyst being used
What are the properties of high density polyethene
The chain don’t pack well
High melting point
Give two solutions of solving pollution by plastics
Mechanical recycling
Feedstock recycling
What happens in mechanical recycling
The plastic types are separated
They are washed sorted and grounded into small pellets
They are melted and remoulded
What is feedstock recycling
Plastics are heated to a temperature that causes the polymer bonds to break to create monomers
The monomers are used to create new plastics
What issues are their with recycling plastics
By heating plastics consistently the chains break each time and becom shorter resulting in plastic properties degrading
What mechanism is involved when converting back into a double state reagents
Elimination and hot and ethanolic
