Alkenes

What are they?

Unsaturated hydrocarbon. Contains at least one C=C double bond.

Alkenes are more reactive than…

alkanes

Formula

CnH2n

How are polymers formed?

Alkenes react with other Alkenes.

Reaction name for making polymers …

Addition polymers

What is a monomer?

The unit which breaks its double bond.

What is a polymer?

A long chain of repeating monomer units joined together.

What are the two forms of poly(ethene)?

High density and low density. HDPE and LDPE

High density. HDPE

• Less flexible

• Kitchenware and buckets

• 60*C and 2 atm

Low density LDPE

• More flexible

• Plastic bags and plastic bottles

• 200*C and 2000atm

Polystyrene also know as

Poly(phenylethene)

poly(chloroethene)

Commonly called PVC or polyvinylchloride

Use of PVC

It’s a rigid plastic. Used for windows and door frames. Difference in usage is due to the presence of a plasticiser.

Why would you expect to find a plasticiser in the PVC to insulate electrical cables?

To allow it to bend.

Why are addition polymers unreactive?

They no longer have a carbon-carbon double bond. They have become unreactive alkane molecules.

Bonding to join atoms to each other in individual polymer molecules?

Strong covalent bonds

What intermolecular force occurs between the polymer molecules?

Weak van der waals

Reactions of Alkenes

Electrophilic addition

What are electrophiles?

Substances which can accept a pair of electrons. Polar molecules with high electronegativity like HBr.

Where is there high electron density?

The double bond between the C=C. Therefore the electrons move from here to the delta + side if the electrophile. Then bond between the electrophile from middle to delta -.

The type of fission?

The bond in the ejector-hike has broken unevenly, therefore heterolytic fission.

The Electrophilic addition of HBr to an alkene produces the addition product …

Halogenoalkane

Ethene + H2O (steam) »

Ethanol. Hydration reaction due to the addition of a water molecule. Using concentrated phosphoric acid as a catalyst. Reaction mixture has conditions 60atm and 600K.