3.3.4 Alkenes Flashcards
Basic alkenes facts
They are unsaturated hydrocarbons
Cnh2n
Ethene is planar
Structure of an alkane
No rotation about a double bond
There is a p orbital containing one electron on each side they look like figures of (there are 2)
The two orbitals overlap to form an electron density cloud above and below
Pie orbitals are above and below horizontally
e/z isomerism
Same molecular formula different arrangement in space
Properties of alkenes
Van der waals act between molecules
Alkenes are not soluble in water as non polar
Alkenes more reactive than alkanes
Electron rich area in the middle attracts electrophiles
Electrophiles
Positively charged reagents
Electron pair acceptors
carbocation
Carbon And an incomplete shell
Electrophilic addition - hydrogen halides
- arrow from the couble bind to the pos element of the h - halogen, halogen2
- then the br- left over attackes to the c+
- makes a haloalkane
Asymmetric alkanes (ABOUT ALKYL GROUPS)
Alkyl groups have a tendency to release electrons - positive and negative effect
The more alkyl groups attached the more stable it is
Can be primary,secondary and…
How to draw a polymer unit from a polymer
Add square brackets
Can only be two carbons in the middle in polymer unit notation
Plasticizers
Small molecules that go between changes to pull them apart. So that they can slide over each other
How plastics are modified
Biodegradability of plastics
Polyalkenes - c-c backbone
Non polar and unreactive so don’t biodegrade
Ldpe how make
Polymerisation ethene at high temp and high pressure by free radical mechanisms (flexible as branched)
Hdpe how make
Polymerisation ethene at low temperature and low pressure
Natta catalyst
Packed tightly together
Types of recycling of plastics
Mechanical (separated - washed - recycled )
Feedstock (heat to make m=monomer - reduced to make polymers )(no good for thermosetting polymers)
Addition reaction with h2so4
1, same reaction as electrophilic addition
but the h+ is the h attached to the o
