Simple11C-labelled molecules which are formed by hot processes following the14N(p, a)11C nuclear reactions with 13 MeV protons in cyclotron targets are of interest as precursors for the synthesis of11C-radiopharma-ceuticals. Solid targets show the advantage of greater stability against radiolysis and heat and a greater variability of chemical reactions. Frozen ammonia NH3, ammonium halides NH4X (X = F, C1, Br, I), and complex salts such as Co(NH3)eCl3have been studied as matrices. The interaction of recoil carbon atoms with the lattice constituents leads to a very differentiated spectrum of11C containing compounds. Analysis of the system is performed by gas chromatography or high performance liquid chromatography. In contrast to the situation in alkali halides, the carbon atoms react to organic compounds such as11C(NH)2-cyanamide,11CH3NH3+-methylammonium,11CH(NH2)2+-formamidinium and11C(NH2)3+-guanidinium with radiochemical yields of 40%, 80%, 30% and 65%, respectively. Even at 5 K, carbon stabilizes via H-abstraction to CNn-radicals and insertion into N-H bonds. The amount of ammonium ions interacting with the carbon depends strongly on the lattice arrangement. This could be shown by experiments in different lattice structures, using low temperature cryostats. The above mentioned products can be transferred to11C labelled compounds such as pyrimidine-derivatives and barbiturates suited for nuclear medical applications. Moreover, the behaviour of carbon impurities in ionic crystals may serve as a model for the formation of organic compounds in inorganic matter.