Solventless and solid-state reactions as applied to the meteoritic chemistry

Most chemical reactions on asteroids, from which meteors and meteorites originate, are hypothesized to occur primarily in the solid mixtures. Some secondary chemical reactions may have occurred during the periods of the aqueous alteration of the asteroids. A myriad of organic compounds have been isolated from the meteorites, but the chemical pathways by which they were formed are only partially elucidated. In this paper we propose that many meteoritic organic compounds were formed in the solventless and solid-state reactions, which were only recently explored in the conjunction with the green chemistry (environmentally friendly). A typical solventless approach exploits the phenomenon of the mixed melting points. As the solid materials are mixed together, the melting point of the mixture becomes lower than the melting points of its individual components. In some cases the entire mixture may melt upon mixing. The reactions would then occur in a viscous melted state. In the traditional solid-state reactions the solids are mixed together, which allows for the intimate contact of the reactants, but the reaction occurs without melting. Numerous examples of the known solventless and solid-state reactions which are particularly relevant to the meteoritic chemistry are described.