Alkenes Flashcards
Pi bond
Sideways overlap of adjacent p orbitals above and below the plane of the molecule.
Sigma bond
Direct overlap of orbitals between bonding atoms
E/Z isomerism displayed in…
Two different groups are attached to both carbons of a double bond as the double bond restricts rotation.
Stereoisomerism
Molecules with the same structural formula but a different arrangement of atoms in space.
Cis trans isomerism
A special case of EZ isomerism in which two of the substituting groups attached to each carbon atom of the C=C group are the same.
Eg. In E-but-2-ene (trans)
And Z-but-2-ene (cis)
Reaction of alkene with hydrogen
Reactants: alkene and H2
Conditions: nickel catalyst and high temperature and pressure
Products: alkane
Reaction of halide with alkene
At RTP produces dihaloalkane
Reaction of alkene with hydrogen halide
Best under reflux makes haloalkane
Reaction of alkene with water
High temperature (steam) and H3PO4 catalyst producing alcohol
Electrophile
An electron pair acceptor
Addition reaction
Adding together two molecules to make a third molecule
Intermediate carbocation
Containing carbon atom with a positive charge formed during the reaction
Markownikoff’s rule
When a hydrogen halide is added to an unsymmetrical alkene, the most likely product is the one in which the H atom adds to the carbon that already has the most Hs attached, the most stable carbocation is the one most likely to form an intermediate.
Reason why bonding in alkenes makes them susceptible to attsck y electrophiles
The Pi bond is above and below the plane of the nucleus and so weak so can more easily be attracted to and broken by electrophiles.
atom economy
Mr of required products/total Mr of reactants X 100%
