Abstract

Hydrogen cyanide (HCN) has emerged one of the key molecules for the synthesis of major building blocks of life – lipids, sugars and nucleotides – through a series of chemical reactions, some mediated by ultraviolet light along with other scenarios. The amount of cyanide available in a natural environment can be predicted from the rate at which it is produced in an environment plus the rate it is introduced to the environment, versus the rates it is destroyed and leaves the environment. One of the most important mechanisms of HCN loss is hydrolysis and it depends on the physical and chemical conditions of the environment. I will present the most comprehensive study thus far of the hydrolysis of HCN . I explore hydrolysis across a range of temperatures, pH and in the presence of salts like sulfite, sulfide and phosphate. We determine the degradation rate of HCN for this range of conditions and predict the rate constants for acid-catalyzed hydrolysis and base-catalyzed hydrolysis, along with uncertainties. These uncertainties are critical for comparing our results to similar studies and applying our results to environmental conditions. We find that in the neutral to alkaline conditions, the hydrolysis rates are comparable to literature within the error limits. However, in acidic conditions the rates are slower with lower activation energy (49.7±4 KJ/mol). We apply our results, in comparison to a variety of cyanide sources found in the literature to provide new predictions of cyanide availability in natural waters. Our results are critical for constraining the prebiotic environment where the prebiotic synthesis of amino acids, nucleotides and phospholipids could have occurred.