properties of alkene Flashcards
Why do double bonds make alkenes reactive
sigma have a high electron density
Pi bond has a relatively low bond enthalpy
Easy to break, more reactive
What is different about cycloalkenes
Have 2 fewer hydrogens
What do double bonds contain
Pi bond and sigma bonds
When do sigma bonds happen
When 2 s orbitals overlap.
They align horizontally to give a single covalent bond
Sigma bond properties
Strong electrostatic force of attraction between nuclei and shared pairs of electrons due to high electron density between nuclei
Has a high bond enthalpy
What are pi bonds
Parallel overlap of 2 p orbitals above and below the bonding c atoms
Why are pi bonds weaker than sigma bonds
Electron density is spread out above and below the nuclei. The electrostatic attraction is weaker so they have a weaker bond enthaply making them more reactive
Why are alkanes less reactive
Only have sigma bonds
They are non polar
What are alkenes good for
Polymers and petrochemicals
Why are alkenes open to attack from electrophiles
Pi bond sticks out a little and the whole double bond has a high electron density
Electrophile adds to the molecule
What does stereoisomerism occur on
Alkenes
contain double bond
Atoms cant rotate around the double c bond and is rigid
Stereoisomers meaning
Same structural formula but the different arrangement in atoms
What are electrophiles
Electron pair acceptor
Deficient in electrons
Example of electrophiles
delta positive polar bonds, positive ions
Test for alkenes
Bromine water - orange to colorless
electrophilic addition hydrogen gas with ethene conditions
150 degrees, nickel catalyst,
make ethane
What does the hydration of alkenes make
alcohol
hydration of alkene conditions
steam and acid catalyst
What do alkenes reacted with hydrogen halides make
halogenoalkanes
Landfill is useful for disposing plastics that
- are too difficult to recycle
- Too difficult to separate from other materials
- Not enough plastic to extract it
Why is it hard to dispose of polymers
Not biodegradable
what recycled plastic can be used for
plastics cracked into monomers and used as an organic feedstock for plastic or other substances
Some plastics can be remoulded
When is incineration used to dispose of plastic
plastic cant be recycled
energy from burning used to generate energy
Why is burning plastic bad
Can release toxic fumes
Chlorine-based plastics produce harmful HCL gas when burned.
Flue gas scrubbers used to neutralise acidic gases by firing a base
