AS.12 Alkenes Flashcards
Alkenes orbitals
Sigma bonds - end on overlap
Pi bonds - side on overlap
Double bond is a combination of both
Stereoisomerism
Molecules with same structural formula but the atoms are arranged differently in space
Why are there stereoisomers
C=C bond is non rotational
R groups are in fixed positions
E isomer
High priority groups are on OPPOSITE sides
Z isomer
High priority groups are on SAME side
Priority is based on…..
Atomic number of immediate atom bonded to carbon in the double bond
Cis/trans isomerism
Each c of double bond must have an identical group
Trans isomerism
The same groups are on OPPOSITE sides
Cis
The same groups are on the SAME side
Carbocation stability
The more stable cation is more preferred by mechanism so major product
Primary ——————> tertiary
Increasing stability
Primary - carbocation is bonded to one carbon atom
Tertiary - carbocation is bonded to three carbon atoms
Disposal of waste polymers
Landfills
Recycle and reuse
+allows new materials
-expensive
Combustion for energy production
+used to heat water for power turbines
-could release toxic gases e.g. HCl
Use as organic feedstock
+doesn’t require cleaning and separating polymers
-very expensive
Alternative solutions for waste polymers
Use more biodegradable polymers
+plant sources such as cellulose
-would take away space for crops
Use more photodegradable polymers
+bonds are weakened by absorbing light
-longevity is questionable
Electrophile
Electron pair acceptor
How is the dipole induced in electrophillic substitution
High electron density of c=c
How electrophiles work
Accepts a pair of e-
