Organic chemistry / by Frank C. Whitmore.

  • Frank C. Whitmore
Date:
1937
Catalogue details

Licence: In copyright

Credit: Organic chemistry / by Frank C. Whitmore. Source: Wellcome Collection.

    47/1104 page 31
    action of heated aluminum oxide, etc. This last method, using a mixture of superheated steam and ethanol passed over kaolin was employed for making ethylene for the preparation of “mus- tard gas” (/S/S'-dichlorodiethylsulfide) during the World War. 2. By removal of halogen acid from an ethyl halide by means of an alcoholic solution of a base, usually potassium hydroxide. The yield of olefin is lessened by the simultaneous formation of an ether corresponding to the alkyl halide and the alcohol used. At least two explanations have been proposed for this side reaction. One involves the following equilibrium EtOH + KOH EtOK + H20 The 'potassium, ethylate can then react with the ethyl halide to give diethyl ether (Williamson reaction). Another explanation assumes the dissociation of the ethyl halide into a free radical containing bivalent carbon, ethylidene, CH3CH= (Nef). This is so reactive that it is incapable of independent existence. Part of its rearranges to H2C = CH2 and part of it adds ethyl alcohol to form diethyl ether. The complexity of the process can be seen from the fact that neopentyl iodide with alcoholic KOH gives mainly neopentane (p. 73). 3. By removal of two halogen atoms from an ethylene halide, XCH2CH2X by means of zinc or magnesium. A modification of this method depends on the fact that ethylene iodide loses its iodine on heating and forms ethylene. Thus if ethylene bromide is heated with an alcoholic solution of potassium iodide the products are potassium bromide, iodine and ethylene. 4. By electrolysis of sodium succinate solution (Kolbe). 5. The large amount of ethylene used for making ethylene glycol and the many related commercial products (some 50 in 1936) has been prepared by cracking fairly pure propane from natural gas (Cameron 1932). The accompanying methane is used to supply part of the heat for the cracking process. The present tendency is to locate plants using ethylene near the large petroleum refineries where enormous amounts of this gas are available in the “cracked gases” (EP 120). The reactions of ethylene are characteristic of compounds con- taining a double bond between carbon atoms.
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