Butadiene
(also divinyl), an organic compound, CH2=CH—CH=CH2. A colorless gas with a characteristic odor, it has a melting point of -108.9° C, a boiling point of -4.5° C, and a density of 0.650 g/cm3 at -6° C. Butadiene is not readily soluble in water but is in alcohol and kerosene. A mixture of air and butadiene, containing 1.6-10.8 percent butadiene, is explosive. Its flash point is -40° C; the maximum acceptable concentration in air is 0.1 g/m3. Butadiene adds hydrogen, the halogens, hydrogenhalides, and other electrophilic rcegents usually in the 1, 4 positions:
and also maleic anhydride to form the anhydride of tetrahydrophthalic acid (quantitative analysis reaction for determining the presence of butadiene).
Butadiene polymerizes and copolymerizes easily to form valuable elastomers (butadiene rubbers, butadiene-acrylonitrile rubbers, butadiene-styrene rubbers, vinyl pyridine rubbers).
The most promising industrial method of producing butadiene is catalytic dehydration of normal butane and butenes contained in the gases of the oil-refining process and in byproduct gases; the process is carried out in one or two stages. Methods are being developed for the oxidative dehydration of normal butane and butylenes. This will make it possible to substantially increase the yield of butadiene. It is also produced by passing the vapor of ethyl alcohol over a mixed dehydration-dehydrogenation catalyst (the S. V. Lebedev method). Butadiene is a byproduct of the production of ethylene and other olefins of gases formed during the pyrolysis of petroleum products.