Preparation & Purification of a HALOGENOALKANE
Step One: Preparation
React an ALCOHOL with CONCENTRATED HYDROCHLORIC ACID (HCl),
this is a SUBSTITUTION reaction: Cl replaces the OH group in the alcohol.
eg. (CH₃)₃C-OH + HCl → (CH₃)₃C-Cl + H₂O
This should be carried out in a separating funnel; keep releasing the pressure, because the product is volatile- it evaporates easily, which raises the pressure in the funnel)
Step Two: Separation
The halogenoalkane produced is INSOLUBLE, so it can be separated from the aqueous reaction mixture using a SEPARATING FUNNEL after it has been allowed to separate into layers.
Run off the AQUEOUS lower layer, leaving the IMPURE HALOGENOALKANE.
Step Three: Purification
In order to get a pure halogenoalkane, 3 things must be removed: excess acid, water and alcohol.
a) Shake the halogenoalkane with NaHCO₃(aq) (SODIUM HYDROGENCARBONATE SOLUTION), to remove any ACIDIC IMPURITIES.
b) Shake the halogenoalkane with WATER to remove SOLUBLE IONIC IMPURITIES.
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c) Remove traces of WATER by DRYING with ANHYDROUS SODIUM SULPHATE (a drying agent)
d) DISTIL the solution: collect any liquid that distils over the BOILING POINT of the DESIRED PRODUCT. This separates the HALOGENOALKANE from other volatile liquids (such as unreacted alcohol), confirming its identity.