VI. Researches on the hydrocarbons of the series C n H 2 n +2 .— No. III

Abstract

Iodide of isopropyl is not perceptibly acted upon by sodium even if the liquid is heated to the boiling-point; but if anhydrous ether perfectly free from alcohol is added, a reaction soon commences without application of external heat; the liquid becomes warm, and the iodide is decomposed with formation of iodide of sodium. The chief products of this reaction are, (1) propylene; from which bromide of propylene was obtained by passing the gases which are evolved through bromine; (2) a gaseous hydrocarbon, which is not absorbed by bromine and which burns with a luminous flame, probably consisting of hydride of propyl; and (3) a liquid hydrocarbon, which, according to its composition and mode of formation, must be considered as di-isopropyl. By the following method I obtained the largest yield of this liquid. A flask holding about 250 cub. centims. was half filled with iodide of isopropyl (which had been prepared by acting with hydroiodic acid upon glycerin); an equivalent quantity of sodium cut into thin pieces was added, upon this a layer of pure ether was poured, and the flask quickly connected with the lower end of a Liebig’s condenser. Where the two liquids meet, a brisk reaction soon sets in; the escaping gases carry off a large quantity of the liquid, chiefly of the more volatile ether, and it is therefore necessary to keep the condenser as cold as possible. The reaction goes on generally quietly until the greatest portion of the iodide is decomposed; if it stops after a short time, gentle heat has to be applied as long as gas is evolved. After the reaction is over, the flask is heated in an oil-bath, and the liquid contents are distilled off. The distillate is fractionated several times, and the portion boiling between 50° and 70° C. collected separately. This consists chiefly of di-isopropyl, but also contains ether, undecomposed iodide of isopropyl, and may also contain diallyl if the iodide was not quite pure. In order to remove these admixtures, the liquid is repeatedly shaken with concentrated sulphuric acid as long as heat is evolved, then rectified, and the distillate treated with a mixture of strong nitric and sulphuric acid as long as iodine separates, then washed, dried, and rectified over potassium.