Question

Lab method of ethyl bromide chemical reaction

Answer 1

E THYL BROMIDE - M ETHOD 1 1
100 grms potassium bromide
100 grms (54 mL) conc. sulphuric acid
60 grms (75 mL) absolute alcohol
Fit up the apparatus as shown. The distilling flask should have a capacity of not less than 1 litre, and is attached to a long condenser. An adapter is fixed to the end of the condenser, dipping into a conical flask (250 mL), which serves as receiver. The alcohol and sulphuric acid are mixed in the distilling flask and cooled to the ordinary temperature tinder the tap. The potassium bromide, coarsely powdered, is then added. The flask, which is closed with a cork, is fixed to the condenser and heated on the sand-bath. A sufficient quantity of water is poured into the receiver to close the end of the adapter. After a short time the liquid in the flask begins to boil and froth up, and the ethyl bromide, in the form of heavy drops of colourless liquid, distils and collects at the bottom of the receiver. If the liquid threatens to froth over, the flask must be raised from the sand-bath for a moment. The distillation is continued until no further drops of oil appear at the end of the condenser. As the ethyl bromide has a low boiling point (38-39°C), it is desirable to surround the receiver with ice during this operation. The distillate is now removed and poured into a separating funnel, and the lower layer of ethyl bromide separated. The water is thrown away and the ethyl bromide poured back together with about an equal bulk of dilute sodium carbonate solution and shaken up. The ethyl bromide is withdrawn, as before, and again shaken up with water. Finally, it is carefully separated from the water and run into a dry distilling flask. The small quantity of water which remains. and renders the liquid turbid, is removed by adding a dehydrating agent.
Dehydration
Moisture can be readily removed from liquids by adding a solid hygroscopic substance which does not act chemically upon the liquid. The common dehydrating agents are calcium chloride, potassium carbonate, sodium sulphate (anhydrous), quicklime, etc. Alkalis can not of course be used for dehydrating organic acids, nor can calcium chloride be employed in conjunction with alcohols or organic bases, with which it combines. In the present instance it can be used. A few small pieces of the granulated or fused calcium chloride are added to the liquid. The flask is corked and left to stand for some hours until the liquid becomes clear. It is then distilled. A thermometer is inserted into the neck of the flask with the bulb just below the side tube. The flask is attached to a condenser and heated gently on the water bath, so that the liquid distils at a moderate speed (2-3 drops a second). The temperature is noted and the portion boiling at 35-43°C collected in a separate flask. This consists of ethyl bromide which may contain a little ether. Yield 75-80 grams.