Model Studies on the Formation and Reactions of Solid Glycine Complexes at the Coasts of a Primordial Salty Ocean

Abstract

Abstract Laboratory experiments pertinent to the prebiotic hot‐volcanic‐coast scenario are described. When artificial primordial seawater which contained NaCl, KCl, MgCl 2 , CaCl 2 , and a small amount of glycine (Hgly) was evaporated to dryness, it was found that in the remaining solid salt mixture the amino acid was exclusively present as CaCl 2 (Hgly)·H 2 O ( 1 ). The coordination compound 1 was also obtained by controlled efflorescence of the corresponding trihydrate CaCl 2 (Hgly)·3H 2 O ( 2 ). A characteristic structural feature of crystalline 2 is [CaCl(Hgly)(H 2 O) 3 ] + units that are interconnected to form one‐dimensional coordination polymers. On thermolysis at 350 °C in a nitrogen atmosphere, compound 1 yielded, inter alia, 15 different methylated and ethylated pyrroles. In contrast, the artificial sea salt–glycine mixtures, despite containing 1 , produced no detectable amounts of organics under the same conditions. Hydrochloric acid from thermal hydrolysis of the sea salt component MgCl 2 ·6H 2 O may be responsible for this different behavior. 1 , 2 , and the related compounds CaCl 2 (Hgly) 2 ·4H 2 O ( 3 ), and MgCl 2 (Hgly) 2 ·2H 2 O ( 4 ) have been prepared in analytically pure form on a multi‐gram scale. Methods used in this study were single‐crystal and powder X‐ray diffraction, infrared and Raman spectroscopy, thermogravimetric and differential thermal analysis, and gas chromatography–mass spectrometry.