Sequential GC-MS studies of gas and liquid in equilibrium were the principal measurements made to investigate the cracking of alkanes, the oligomerization of alkenes and the Friedel-Crafts alkylation of benzene and toluene by alkenes, in various ionic liquids. It was shown that alkenes of the same or near half the size of cracked alkanes readily polymerize in the same medium and it is suggested that this is the driving force of the alkane cracking. The acids responsible for these processes in liquid organic haloaluminates and halohydrogenates are all anionic, ranging from the mild HX2-, of limited action, to the more potent superacids XH(Al2X7)(-) and Al2X7. The latter is postulated to act upon an alkane via hydride abstraction, forming AlX3H-, a species stable in Lewis acidic systems, but sensitive to XH(Al2X7)(-). At ambient temperatures alkene polymerization is the fastest of the three processes while alkane cracking is slow, but requires less acidic conditions. (C) 2004 Elsevier B.V. All rights reserved.