Organic 2 Review Problem 104

Organic 2 Review Problem 104 - rapid reaction occurs,...

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88 PRACTICAL ORGANIC CHEMISTRY To prepare pure acetylene, assemble the apparatus shown in Fig. 57. F is a wide-necked 300 ml. bolt-head flask, to which is fitted a double-surface reflux water-condenser C and the dropping- funnel D. From the top of C, a delivery-tube leads down to the pneumatic trough T, where the gas can be collected in jars in the usual way. (Alternatively, use the apparatus shown in Fig. FIG. 57. p. 45.) Place ioo ml. of rectified spirit and 25 g. of powdered potassium hydroxide in F, and boil the mixture gently under reflux until the potash is almost entirely dissolved. Then place 15 ml. (33 g.) of i,2-dibromoethanc in D, and allow the dibro- mide to fall drop by drop into the boiling solution in F. A
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Unformatted text preview: rapid reaction occurs, acetylene being generated and potassium bromide precipitated. Test the gas issuing from the delivery-tube in the usual way to ensure that all air has been displaced by acetylene. Then collect the pure acetylene in gas-jars. Note that this acetylene is almost odourless. Ethylene can be similarly prepared by the action of ethanolic potash on ethyl bromide, but the yield is usually very low. Absolute Ethanol. Supplies of absolute cthanol, which is frequently required in organic chemical work, arc now freely available commer-cially as a result of azeotropic distillation methods. If however it should be...
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