3.4 Alkenes Flashcards
What causes the geometric isomerism in alkenes?
The C=C bond, as there is no free rotation around this bond
What is an (E) isomer?
An isomer where the highest priority groups are on different sides of the double bond
What is a (Z) isomer?
An isomer when the highest priority groups are on the same side of the double bond
What decides the priority of an atom?
If it has the highest atomic number
Describe the electrophillic addition mechanism
An arrow goes from the double bond in ethene to the delta+ hydrogen in an HBr (or other halogen). An arrow goes from the bond between the hydrogen and the halogen to the halogen. The hydrogen goes to one of the carbons in the ethene, leaving a halogen, and a positive ethene molecule. The negative halogen is then attracted to the positive carbon and bonds to this, forming a haloalkane
What decides which carbon will be positive during electrophillic addition?
The most stable carbocation will be positive, meaning the carbon with the most carbons surrounding it.
What things are polymers are used to make?
Bags, bottles, CDs, DVDs, the casing of electrical items, etc.
What is addition polymerisation?
When monomers join together, forming no other molecules/ products
Describe the structure of low-density poly ethene
Some polymer chains have side branches, stopping the molecules from lining up regularly. This means that the material is less strong and has a lower melting point
Describe the structure of high-density polyethene
The molecules do not have side branches, so they line up regularly to form a crystalline structure, meaning the material has a higher density, the forces of attraction between molecules are stronger, has a high melting point.
What test can be done for alkenes?
Aqueous bromine water, changin from red-brown to colourless solution
