ARCHEAN GEOCHEMISTRY OF FORMALDEHYDE AND CYANIDE AND THE OLIGOMERIZATION OF CYANOHYDRIN

The sources and speciation of reduced carbon and nitrogen inferred for the early Archean are reviewed in terms of current observations and m odels, and known chemical reactions. Within this framework hydrogen cy anide and cyanide ion in significant concentration would have been eli minated by reaction with excess formaldehyde to form cyanohydrin (glyc olonitrile), and with ferrous ion to form ferrocyanide. Natural reacti ons of these molecules would under such conditions deserve special con sideration in modeling of primordial organochemical processes. As a st ep in this direction, transformation reactions have been investigated involving glycolonitrile in the presence of water. We find that glycol onitrile, formed from formaldehyde and hydrogen cyanide or cyanide ion , spontaneously cyclodimerizes to 4-amino-2-hydroxymethyloxazole. The crystalline dimer is the major product at low temperature (approximate ly 0-degrees-C); the yield diminishes with increasing temperature at t he expense of polymerization and hydrolysis products. Hydrolysis of gl ycolonitrile and of oxazole yields a number of simpler organic molecul es, including ammonia and glycolamide. The spontaneous polymerization of glycolonitrile and its dimer gives rise to soluble, cationic oligom ers of as yet unknown structure, and, unless arrested, to a viscous li quid, insoluble in water. A loss of cyanide by reaction with formaldeh yde, inferred for the early terrestrial hydrosphere and cryosphere wou ld present a dilemma for hypotheses invoking cyanide and related compo unds as concentrated reactants capable of forming biomolecular precurs or species. Attempts to escape from its horns may take advantage of th e efficient concentration and separation of cyanide as solid ferriferr ocyanide, and most directly of reactions of glycolonitrile and its der ivatives.