Substitution Reactions Flashcards
What is homolytic fission?
In homolytic fission two electrically uncharged radicals are formed. Radicals are particles that have an unpaired electron. They are very reactive
What happens when a halogen reacts with an alkane?
Halogenoalkanes are formed. Free radical substitution
What are the conditions for free radical substitution?
Ultraviolet light
What are the three steps of a free radical substitution reaction?
Initiation, propagation and termination
What happens in the initiation phase?
Free radicals are produced.
1) sunlight provides enough energy to break the halogen-halogen bond.
2) the bond splits equally and each atom gets to keep one electron. Homolytic fission. The atom becomes a highly reactive free radical due to its unpaired electron.
What happens in a propagation reaction?
Fee radicals are used up and created in a chain reaction.
What happens in the propagation reaction when chlorine free radicals reacts with methane?
1) Cl* free radical attacks methane molecule. Cl* + CH4 ♐️CH3+ HCl
2) the new methyl free radical can attack another cl2 molecule. CH3 + Cl2 ♐️ CH3Cl + Cl
3) the new Cl can attack another CH4 molecule and so on and so forth
What happens in the termination reaction?
The free radicals are mopped up
If two free radicals join together, they make a stable molecule.
What is the problem with substitution reactions?
You get a mixture of products.
What is heterolytic fission?
In heterolytic fission, two different substances are formed. A positively charged cation and a negatively charged anion.
