HYDROCARBON GASES AND AROMATIC-HYDROCARBONS PRODUCED BY IMPACT SHOCK FROM FROZEN BENZENE - COSMOCHEMICAL SIGNIFICANCE

Shock waves trigger reactions in solid benzene at 77 K to produce hydrogen, light alkanes from C-1 to C-3, light alkenes from C-2 to C-3, acetylene, aromatic hydrocarbons with high-molecular weights ranging from 102 (phenylacetylene) to 306 (quaterphenyl), and unknown carbonaceous materials. These products are similar to those yielded by rapidly quenched pyrolysis. Shock synthesis favours the formation of compounds with metapositions in these structural isomers. The reaction mechanism producing aromatic hydrocarbons with low molecular weights is vague at present, but it cannot be a simple radical reaction. Most of shock-derived products are detected in carbonaceous chondrites. These results suggest that many sorts of hydrocarbons in solar materials such as meteorites have been produced by frequent and violent shocks throughout the history of the solar system. In particular, this process may be responsible for the formation of extraterrestrial unsaturated hydrocarbon gases.