alkenes Flashcards
saturated?
no
functional group
Cn H2n
H arrangement
planar, 120 degrees
pi bond
exposed
high electron density
vulnerable to electrophiles
stereoisomerism
same structural formula, different spatial arrangement, E-Z
electrophile
electron pair acceptors
positive ions or polar molecules
bromine water
orange to colourless
bromine added across C=C
Br polarised by negative charge and accepts electron pair and bonds to C.
Leaves Br- and Carboncation
room temp
most stable carbocation
tertiary
most likely to form
Sulphuric acid stage 1
C=C electrons to H+
:OSO2OH- to C+
forms alkyl hydrogensulfate
sulphuric acid stage 2
cold water, then heat
forms alcohol
hydrolysis
H2SO4 released; catalyst
hydrogen bromide
forms halogenoalkane
H-Br is polar
H attracted to C=C
C=C electrons to H
H-Br bond electrons to Br
Br- to C+
why are polymers unreactive
strong C-C and C-H
when are addition polymers formed
pi electrons in substituted alkene monomers form C-C bonds between molecules
saturated, unreactive
main reaction to make addition polymers
combustion
are addition polymers biodegradable
no
properties of polymers
non polar
vdw
longer- closer-stronger vdw
long straight chains are strong, short branched are weak and flexible
uses of polymers
unreactive
strong non polar covalent bonds
plastics
modifying polymers
add plasticiser to make more flexible
plasticiser molecules get between chains and push apart and decrease strength of intermolecular forces; easier to bend
reaction conditions
high pressure and temp
lower pressure and temp for straight chain
low density polyethene
branched and softens at lower temps
poly(chloroethene)
PVC
plasticiser
long, closely packed polymer chains. hard and brittle at room temp
used for drain pipes and window frames
plasticised PVC is more flexible; for electrical cable insulation, flooring tiles and clothing.
