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saturated hydrocarbons with the general formula C4H10; colorless and odorless gases. Two isomeric butanes are known: normal, CH3CH2CH2CH3; and isobutane, with boiling points of -0.5° C and -11° C
respectively. Mixtures of these compounds with air that contain 1.5-8.5 percent normal butane or 1.8-8.4 percent isobutane are explosive.
Sources of butanes include petroleum gases, the butane-butylene fraction of refinery gases, and natural gas. Considerable quantities of isobutane are obtained by isomerization of normal butane (in the presence of AICI3 and HCl at 90-105° C and a pressure of 1-2 meganewtons per sq m, or 10-20 kilograms-force per sq cm). Under industrial conditions, butadiene and isobutylene are obtained by dehydrogenation from normal butane and isobutane respectively. Neohexane and isooctane, valuable motor fuel additives, are synthesized from isobutane by alkylation with olefins. Butanes are also used as gas fuel when mixed with propane and other hydrocarbons.