Organic compounds would need to be concentrated and complexified by environmental mechanisms. 1 The origin of life remains unexplained despite decades (or perhaps centuries, depending on where one historically marks the starting point) of research.
In some syntheses, the concentrations must be so high (e.g., 10 M formaldehyde) that the syntheses could not be expected to have occurred on the primitive Earth. Reactions under these and other extreme conditions cannot be
considered plausibly prebiotic. Following important biological compounds do not have adequate prebiotic syntheses:
Coenzymes are essential across all domains of life. B vitamins (B1-thiamin, B2- riboflavin, B3-niacin, B5-pantothenate, B6-pyridoxine, B7-biotin, and B12-cobalamin) represent the largest class of coenzymes, which participate in a diverse set of reactions including C1-rearrangements, DNA repair, electron transfer, and fatty acid synthesis. 2
6. pyridoxal folic acid
Vitamin B6 is one of the most central molecules in cells of living organisms. It is a critical co-factor for a diverse range of biochemical reactions that regulate basic cellular metabolism, which impact overall physiology. 3
Biotin, thiamine, and CoA are essential cofactors 4
8. lipoic acid
9. Straight-chain fatty acids
High concentrations of osmotically active salts inhibit the ability of membranous vesicles to form because the internal volume cannot increase unless the membrane is sufficiently permeable for the salt to equilibrate between the internal and external phases. The other problem occurs if the external medium becomes diluted. As a result, the compartment swells as water diffuses inward across the boundary membrane and may even burst, releasing the internal contents.
Gaseous NH3 is rapidly decomposed by ultraviolet light, and during Archean times, the absence of a significant ozone layer would have limited NH3's atmospheric concentration. 1 Without added H2, amino acid yields are quite low, especially when CO2 is the sole carbon source
Lipids and Membrane-Forming Compounds
Most prebiotic simulations don't generate large amounts of fatty acids, with the exception of some hydrothermal vent simulations, which may use concentrations of reactants which are unreasonably high for these environments. The Murchison CC contains small amounts of straight-chain fatty acids, though some of these may be contamination. 5