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Haloalkanes

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 –               C2F2Cl→ C2F2Cl • + •Cl

propogation –        •Cl + O3 → •Cl O + O2

•Cl O + O → •Cl + O

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