unit 4-Alkenes Flashcards
What is a π-bond?
The sideways overlap of two p-orbitals.
What is the shape and bond angle around each double bonded carbon & why?
Trigonal planar, 120, 3 bonding regions.
What is a stereoisomer?
Molecules with the same structural formula but a different arrangements of atoms in space.
Why are double bonded carbons not able to move freely?
The π-bond’s electron density is concentrated above and below the plane of the sigma-bond.
Why do alkenes have stereoisomers?
Because rotaion about the double bond is restricted.
What conditions must an alkene satisfy to have E/Z isomerism?
(2 points)
(1) A C=C bond
(2) Different groups attached to each carbon atom of the double bond.
When would you use the terms cis and trans instead of E/Z isomerism?
When one of the attached groups on each carbon atom is a hydrogen atom.
Why are alkenes more reactive than alkanes?
The π-bond has a larger electron density than a sigma bond, the fact that the electrons are concentrated outside the double bond means that the π-bond readily breaks so they can undergo addition reactions.
Why are π-bonds weaker than sigma bonds?
The sideways overlap of p-orbitals has a smaller orbital overlap than the overlap of orbitals that form the sigma bond.
What conditions are needed to turn alkenes into alkanes?
150, nickel catalyst.
