3.3.4 Alkenes Flashcards
What is a polymer
are molecules made from a large number of monomers joined together
What is a monomer
The smaller units from which larger molecules are made
What is addition polymerisation
Reaction in which many monomers with c=c form long chain of polymers as the only product
Why are addition polymers unreactive
Non - polar and relatively strong
What are the forces in an Alkene
Van der Waals
Because the chains are non-polar
Give uses of PVC and why
Plastic pipes window frames
Rigid and hard
Why is PVC rigid/hard
Presence of dipole-dipole interactions
Due to difference in electronegativity between chlorine and carbon
How does a plasticiser work
Causes chains to move apart
Weakening intermolecular forces of attraction
Chains become flexible
Formula for alkenes
C2 H2n
Are alkenes saturated or unsaturated
Unsaturated c=c
Why are alkenes highly reactive
Double bond has a high electron density
Pie and sigma bonds
Makes easier to attack
Are alkenes soluble or insoluble in water
Insoluble in water
Which is which E Z isomers
Z isomers together
E isomers opposite
Priority in E Z isomers is determined by
Greater atomic number
(And the order in which bonded)
What forces hold together long polymer chains and why
Van Der Waals
Because chains are non-polar
What are uses of PVC with plasticiser x2
Flooring
Insulation in electrical cables
What types of bonds are found around a c=c and which is where
Sigmas bond between both carbons
Pi bond found around
How is the pi bond caused
Overlap of p orbitals
Alkenes are soluble/insoluble in water
Insoluble
Alkenes are …. Reactive because …..
Highly
Pi bond has high electron density so easier to attack
Bond enthalpy of pi and sigma bonds explained
Pi bond enthalpy less than sigma bond
So pi bond is easier to break so more likely to take part in reactions
Stereoisomers definition
Molecules with the same molecule and structural formula but different arrangement of atoms in space
In what situation would there be non E Z isomers
Think what would the molecule need to have coming off c=c
One side has the same groups on both strands
So on one side two hydrogen etc
What does the stability of an Alkene depend on
The number of alkyl groups that are bonded to the c+ in carbonisation step
Do addition reaction of alkenes
DO IT RN
Flashcards and book
When symmetrical alkenes undergo electrophilic addition how many different products can be formed
Only ONE
can go either side but it would still be the same product rotated
When unsymmetrical alkenes undergo electrophilic addition how many products are formed
+ which is more likely
Two
The hydrogen from the halide is more likely to bind to the carbon which has more hydrogens
What does the stability depend on
The number of alkyl groups attached
Which is most to least stable tertiary secondary primary alkanes
Teritary
Secondary
Primary
The more carbons attached the more stable
If it is more stable it is more likely to form the major/minor product
Major
Test for alkenes
Bromine water
Alkene - Turns from orange to colourless (must say turns)
Alkanes - no observable reaction
How to know which mechanism occurs with hydroxide ion
Nucleophilic Substitution
Primary
Aqueous
Warm
Nucleophilic
Elimination
Concentrated
Hot
Elimination
Ethanol solvent
Tertiary
What is an electrophile
Electron pair acceptor
( they are deficient in electrons )
How is an alkyl hydrogen sulfate converted to an alcohol
Add cold water
Will have alcohol + sulfuric acid
Process called hydrolysis
