Estudo da reação entre tiocianato de amônio e Fe (II) ou Fe (III) utilizando a espectroscopia no infravermelho: um experimento de química prebiótica.

Abstract

The prebiotic chemistry studies the reactions that could be played an important role on origins of life on Earth. However, these reactions should be carried out under conditions that existed on the prebiotic Earth. The laboratory experiments of heating substances in solid state could be corresponding to the following prebiotic environments: cooling lava from volcanoes on the ground and impact of meteorites or comets on the earth. The present study examined the reaction in solid state between ammonium thiocyanate and Fe (II) or Fe (III). The samples were heated at 220 ºC in several different times (6 hours, 24 hours, 7 days). The most important finding of this work is that a reaction of oxidation-reduction is occurring between Fe (II) and ammonium thiocyanate, the infrared spectrum of the reaction product ammonium thiocyanate/Fe (II) showed a band that it is characteristic of ferricyanate. The infrared spectra also showed bands that they are characteristics of guanidine thiocyanate. Thus, the heating of ammonium thiocyanate with Fe (II) in solid state is synthesizing guanidine thiocyanate and at the same time oxidizing Fe (II) to Fe (III). The product of reaction between Fe (III) and ammonium thiocyanate is guanidine thiocyanate. Fe (II) and Fe (III) are reacting with ammonium thiocyanate in different way.