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 halide

alkene + hh (HCl) → haloalkanes (2 possible products)

addition of Br2 to alkenes - halogenation

alkene + chlorine/bromine RTP → haloalkane

hydration of alkenes

alkenes + steam + phosphoric acid catalyst H3PO4 → major and minor product of alcohol

the mechanism of addition to alkenes

electrohphillic addition

markownikoff’s rule of stability of cation intermediate

the addition of HX to an unsymmetrical alkene, the hydrogen atom attaches to the carbon that already has more hydrogens, forming the more stable carbocation 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