alkenes Flashcards
what are alkenes
unsaturated hydrocarbons with a c=c bond
what is the bond and bond angle around an alkene
planar bond, 120°
alkenes have high electron density therefore ….
high reactivity
what is stereoisomerism
same molecular and structural formula but atoms are arranged differently in space
what 2 rules do stereoisomers require
restricted rotation
2 different atoms/ molecules bonded to each carbon
Cahn Ingold Prelog
(6 points)
-consider the mass of the atoms attatched directly to the left-hand carbon of the c=c bond
-the atoms with the higher number take priority
-if equal, consider the atoms bonded to the carbon one further away
-repeat for the right-hand carbon of the c=c bond
-if both priority groups are on the same side, Z isomerism is present
-if priority groups are on opposite sides, E isomerism is present
what is an electrophile
electron pair acceptor
electrophillic addition is from…
an alkene (breaking the c=c bond)
what are the reagents and conditions required when a halogen halide reacts with an alkene
in its gas phase or aqueous and concentrated
draw the mechanism with ethene and hydrogen bromide
why does an alkene react with bromine water
the electron rich c=c bond induces a temporary delta +ve dipole on one Br so the bond breaks
the lone pair on the other Br is the attracted to the carbocation to form a new bond (a dibromoalkane)
draw the mechanism for ethene and bromine water
what is the reagent and conditions for the reaction between an alkene and sulfuric acid
cold concentrated H2SO4
draw the mechanism for ethene and sulfuric acid
what is the name of the reaction of an alkene with steam
direct hydration
what is the reagent and conditions for steam with an alkene
concentrated H2SO4 catalyst
draw the mechanism for steam and ethene
major products are …
formed from the more stable carbocation
minor products are …
formed from the less stable carbocation
what makes the carbocation more stable
more alkyl groups bonded to the c+
what is addition polymerisation
joining 2 small molecules to form a very large unreactive molecule
what conditions are addition polymers formed under
high temperature, high pressure, from an alkene monomer
what is the repeating unit in an addition polymer
what does PVC stand for
poly(chloro(ethene))
