12 alkenes

sigma and pi bond in an alkene

sigma: head on overlap of orbitals (strong)

pi: side on overlap of p-orbitals (weak)

stereoisomerism (e/z, cis trans)

same structural formula, but different arrangement of the atoms in space

• E/Z occurs when there’s C=C bond, and 2 different groups

• stereoisomers around double bond arises because rotation of the DB is restricted and the groups attached to C atoms are fixed relative to each other

cahn ingold prelog rules

• the atoms attached to each C atom is a DB are given priority by atomic number

• if the groups of higher priority are on the same side of the DB, the compound is a Z isomer

• if groups of higher priority are diagonal, it is a E isomer

electrophile

atom/group accepts a electron pai (partial + charge)

heterolytic bond fission

a atom/group takes both shared electrons

bond enthalpy

take place when breaking by homolytic fission 1 mol of given type of bond in the molecules of a gaseous species

addition of HBr to alkenes

• hydrogen molecules add across the c=c bond

• then db becomes sb then an alkane is formed

• nickel catalyses helps break h-h bonds and H add to C atoms

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addition of Br2 to alkenes

hydration of alkenes

the mechanism of addition to alkenes

electrohphillic addition

markownikoff’s rule c stability of cation intermediate

addition polymerisation of alkenes

• unsaturated alkene molecules undergo addition polymerisation to produce saturated chains with no DB

• high temps and pressure with long chains of alkenes = polymerisation

• eg.polyethene : toys, shampoo bottles (most common polymer)

sustainability of waste polymers

• recycle: can be reused, reducing polymers on landfills

• disposing: non biodegradable, kills marine life

• PVC recycling: hazardous - releases hydrogen chloride (toxic)

• use as fuel: can be incinerated to be heated into steam and generates turbines

• feedstock recycling: reclaims monomers