Free Radical Substitution of Alkanes Flashcards
What are alkanes?
= unreactive molecules
What is the first reason that alkanes are unreactive?
= non-polar
= similar electronegativity
=
What is the second reason that alkanes are unreactive?
= bonds are strong
= requires great deal of energy
What is one way alkanes can react?
= by free radicals
What are free radicals?
= any species with an unpaired electron
= highly reactive species- alkanes can react with free radicals
=
What is free radical substitution?
= a atom from the alkane has been substituted with the halogen atom
What are the 3 stages of the reaction with alkanes and halogens?
= inititation
= propagation
= termination
What happens during initiation?
= shine ultra violent light onto the reaction mix
= the energy causes the single covalent bonds between the 2 halogen atoms to break
= one electron goes to each halogen atom
= has unpaired electron, free radical
What is this type of splitting with the covalent bond?
= homolytic fission
What happens in propogation step 1?
= a halogen free radical reacts with the alkane
= to make an electron pair the halogen free radical takes a atom and one electron from the alkane
= produces halogen free radical with the atom + alkane free radical
What happens in propogation step 2?
= the alkane free radical reacts with the halogen molecule
= form a chain reaction
=
What happens in termination?
= two free radicals react together
= forms a molecule with no unpaired electrons
= stable molecule
What are the different posibilities?
= two free radicals can form a molecule
= 2 alkane free radicals can form another alkane
= alkane and a halogen free radical can react
What is the problem of free radical substitutution?
= side products
