Comparison of psilocin and serotonin Electron Density Maps. In psilocin the sites of negative electron density at the side chain nitrogen and the ring oxygen are closer together than in serotonin; there would be a greater probability of electron transfer at a receptor site, tunneling via the shorter pathway between the ring −OH and side chain N. The strongest acidic pKa for serotonin is 2.15 and its reactivity is 58.18 m³ mol⁻¹, Whereas for psilocin the strongest acidic pKa is 8.97 with a reactivity of 62.42 m³ mol⁻¹ reflecting influence of the tertiary compared to the primary amine and the shift of the hydroxyl⁷. Whilst the possibility of direct electron transfer might be considered depending molecular motion, tunneling in each of these structures would, like in DHA, occur at its unique energy level.