Substitution reactions of haloaklanes:
When a haloalkane is reacted with hot aqueous alkali, a nucleophilic substitution occurs.
It must be refluxed.
To test for the rate of hydrolysis of C-halogen bonds:
1. Add water, to react with the haloalkane to form an alcohol.
2. Adding silver nitrate to the solution will show how fast the reaction occurs, a precipitate forms when the substitution has occurred.
3. The faster the precipitate forms, the weaker the C-halogen bond is (the smaller the bond enthalpy).
4. Iodine forms a yellow precipitate first. Then bromine forms a cream precipitate. Next, chlorine forms a white precipitate.
C-I < C-Br < C-Cl < C-F
Using organohalogen compounds has environmental impacts:
UV radiation breaks down CFCs in the upper atmosphere, resulting in the breakdown of earths protective ozone layer.
initiation – C2F2Cl2 → C2F2Cl • + •Cl
propogation – •Cl + O3 → •Cl O + O2
•Cl O + O → •Cl + O2