Organic 2 Review Problem 192

Organic 2 Review Problem 192 - 176 P RACTICAL O RGANIC C...

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176 PRACTICAL ORGANIC CHEMISTRY in a beaker, so that the hydrogen bromide may be absorbed with- out risk of "sucking back." Ensure that the apparatus is not standing in the direct rays of the sun. Now pour 24 ml. (76 g.) of bromine ( care in manipulation!) down the condenser, and at once replace the calcium chloride tube or the delivery-tube, as a vigorous reaction occurs when the bromine dissolves in the benzene. When the initial evolu- tion of hydrogen bromide slackens, heat the water-bath to 25-30° for one hour, occasionally shaking the contents of the flask: finally raise the temperature of the bath to 65-70° for a further 45 minutes. Now transfer the dark-coloured liquid to a separating-funnel and shake with an e x cess of 10% aqueous sodium hydroxide solution: the heavy lower layer of crude bromobenzene becomes almost colourless at this stage. Run off the bromobenzene, shake it again with water to ensure absence of alkali, and then dry with calcium chloride for 20-30 minutes. Filter through a small fluted filter-paper directly into a 50 ml.
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