13.3 Reactions Of Alkenes Flashcards
Why are alkenes more reactive than alkanes?
Presence of pi bond
Electron density is concentrated above and below the plane of the sigma bond
Pi electrons are more exposed than electrons in the sigma bond
Pi bond breaks readily
Which is weaker - pi bond or sigma bond?
Pi bond - has lower bond enthalpy
Alkenes undergo addition reactions with:
Hydrogen
Halogens
Hydrogen halides
Steam
What is hydrogenation of alkenes?
Alkene is mixed with hydrogen
Conditions for hydrogenation
Nickel catalyst
423K
Which have lower melting points - trans fats or cis fats?
Trans fats
What is halogenation of alkenes?
Alkenes undergo addiction reactions with halogens chlorine or bromine at room temperature
Conditions for halogenation of alkenes
Room temperature
What happens when bromine water is added to an unsaturated organic compound?
The orange colour disappears
Bromine adds across the double bond
What happens if bromine water is added to a saturated organic compound?
No colour change, as there is no addition reaction
How do alkenes react with hydrogen halides when both are gases?
The reaction takes place as both gases are mixed
How do liquid alkenes react with hydrogen halide?
Hydrogen halide is bubbled through the alkene
What happens in hydration reactions of alkenes?
Alcohols are formed
Conditions for hydration of alkenes
H2O as steam
Phosphoric acid catalyst
