Chapter 20 Alkenes Flashcards
Define alkenes
Alkenes are unsaturated organic compounds that contain carbon-carbon double bonds
Define unsaturated
Contain C=C bonds
General formula of Alkenes
CnH2n
Physical properties of alkenes
same as alkanes
Combustion of alkenes
similar to alkanes, can go through complete and incomplete combustion
What is the purpose of addition reaction?
-Form single product
-C=C bonds break to form new single bonds
-Unsaturated to saturated
Purpose of bromination
Test for unsaturation and distinguish alkenes from alkanes
Alkane and alkenes colour change in bromination
If alkene present, present of carbon carbon double bonds, bromination occurs and reddish-brown bromine solution decolurises
If alkane present, no carbon carbon double bonds, bromination does not occur, and bromine solution remains reddish-brown
What happens during hydrogenation
-carbon carbon double bond breaks
-hydrogen hydrogen bonds is added
How does addition polymerisation happen?
At high temperature and pressure, and the presence of catalyst, unsaturated monomers join together form a single large molecule (polymer)
What happens during addition polymerisation?
one of the carbon-carbon double bonds breaks and each monomer forms a single covalent bond with two other monomers
Purpose of polyethene
make plastic bags and clingfirm
How to obtain alkene?
Cracking of petroleum (crude oil)
What is cracking?
breaking down of long chain hydrocarbons into smaller molecules
Conditions of cracking
-high temperature of 600 degree
aluminum oxide catalyst
