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The use of halogenoalkannes is limited by statutory regulation bevause

Many of them are toxic eg. Polychloroalkanes

Others such as chlorofluorocarbons (CFCs) cause damage to Earth’s ozone (O₃) layer.

Example
CCl₂F₂ —> Cl. + CClF₂.   (Reaction 1 - Initiation)
Cl. + O₃ —> ClO. + O2     (Reaction 2 - Propogation)

ClO. + O₃ —> Cl. + 2O2   (Reaction 3 - Propogation)

In the upper atmosphere, CFCs encounter UV radiation, which ruptures the carbon-chloride bond to form a chloride radical. These radicals destroy ozone.

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Round bottom flask - Chemicals (NaOH (aq) and halogenoalkane) are being heated and are therefore evaporating.

Condenser- Evaporated chemicals are being condensed and move back down into the flask. They condensed due to the change in temperature caused by constant flow of water.

Effect on yeild - Yield will be increased as no chemicals are being lost through evaporation.

C₄H₉Br + OH- —> C₄H₉OH + Br-
(1- Bromobutane) + (Hydroxide ion) —> (Butan-1-ol) + (Bromide ion)

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1) Solvents - many RX molecules contain a polar C-X bond so can mix with a range of substances. It is non flammable and can therefore be used in dry cleaning
2) Anaesthetics - many halogenoalkanes are general anaesthetics. Eg the gas halothane
3) Refrigerant- CFCs were used as refrigerants. The heat required to change the liquid to gas is removed from the fridge to cool it.

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Halogenoalkanes = RX (R= carbon chain) (X= Halogen)
RX + NaOH(aq) —> ROH + Na⁺ + X-
Halogenoalkane + Sodium Hydroxide —> Alcohol + Sodium ion + Halide

Reagents: 1) Aqueous sodium hydroxide to break up RX
2) Dilute nitric acid then aqueous silver nitrate to see PPT
Observations: White PPT (chloride)
Cream PPT (bromide)
Yellow PPT (iodide)

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How easily we can substitute halogens (X) in halogenoalkanes depends on bond polarity and bond strength
Bond polarity: C-F > C-Cl > C-Br > C-I
The more polar the C-X bond, the easier it is to substitute X in the halogenoalkanes
Bond lengths: C-I > C-Br > C-Cl > C-F
Bond Strength: C-F > C-Cl > C-Br > C-I
The weaker the bond, the easier it is to break the C-X bond and substitute X.