Alkenes Flashcards
(22 cards)
What is the general formula of an alkene ?
C n H 2n
What is the functional group of an alkene ?
C=C (carbon-carbon double bond)
How do pi bonds form ?
the sideways overlap of p-orbitals
What is a stereoisomer ?
molecules with the same molecular and structural formula but a different arrangement of atoms in space
When do E/Z isomers occur and why ?
- there are two different groups on each C atom on the C=C bond
- because of restricted rotation around the C=C bond
When is an alkene an E isomer ?
when the 2 highest priority groups are on opposite sides
When is an alkene a Z isomer ?
when the 2 highest priority groups are on the same side
What are cis/trans isomers ?
E/Z isomers with a H atom on each C in the C=C bond
What are cis isomers ?
Z isomers (groups on same side)
What are trans isomers ?
E isomers (groups on opposite sides)
How do you assign priority to the groups on the C=C ?
highest atomic number has highest priority
Why are alkenes more reactive than alkanes ?
because the pi bond in alkenes in much weaker than the sigma bond, and so is more easily broken
What is the test and observation for alkenes ?
- add bromine water
- turns from orange to colourless
What is the catalyst for addition of hydrogen ?
nickel
What are the catalyst and conditions for addition of steam ?
- phosphoric acid
- high temperature and pressure
What mechanism do alkenes undergo ?
electrophilic addition
What is an electrophile ?
an electron pair acceptor
What is a carbocation intermediate ?
the organic ion where the C atom has a positive charge
What is the major product ?
the product formed from the most stable carbocation intermediate
How do we deal with polymer waste ?
- sort into types and recycle
- combustion for energy
- organic feedstock
How can toxic fumes like HCl be removed ?
neutralise by adding a base
How have chemists developed solutions to reduce landfill waste ?
they designed biodegradable, compostable and photodegradable polymers
