Laboratory Preparation of Methylamine - QS Study
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Laboratory Preparation of methylamine

Principle: Methylamine is prepared in the laboratory by the action of bromine and caustic potash on acetamide. The reaction takes place in three steps.

CH3 – CO – NH2 + Br2 + 4 KOH → CH3 – NH2 + 2KBr + K2CO3 + 2H2O

Ethamanide                                                     methylamine

Ch3 – NH2 + HCL → Ch3 – NH2*HCL (Methylamine Hydrochloride)

Ch3 – NH2*HCL + KOH → CH3 – NH2 + KCl + H2O

                                                Methylamine

Procedure: Equivalent amounts of bromine and acetamide are taken in a siltation flasks and then 10% caustic potash solution is slowly added until the reddish color of bromine is just discharged. The distillation flask is then fitted with a dropping funnel containing 50% solutions of KOH and a delivery tube bent at right angles. The other end of the delivery tube is connected with a funnel which is kept slightly immersed in dil. HCL in a braker, a 40 % solution of KOH is then added slowly into the flask and the flask is warmed gently on a water bath at 70″C. When the solution in the flask becomes colorless it is distilled. Methylamine distills over and is absorbed in the dilute HCl taken in the beaker to form Methylamine Hydrochloride.

Purification: Methylamine hydrochloride solution in the beaker is then evaporated on a water bath when crystals of methylamine hydrochloride are obtained. These crystals are collected and heated with KOH when pure methylamine distills over.