Mechanism of Prebiotic Uracil Synthesis from Urea and HC₃O⁺ in Space

Mechanisms of interstellar synthesis of glycine, alanine, and serine from aminonitriles, OH, and H2O

“…Because the rate constant of a thermal reaction decreases exponentially with the activation energy, the reaction barrier should be zero 1 or a few kJ mol −1 2,3 at most for the reaction to occur in cold dense clouds. Several mechanisms for barrierless reactions starting from radical–neutral or ion–neutral reactions have been proposed for the synthesis of glycine (NH 2 CH 2 COOH, Gly) 4 and nucleobases 5–7 in this laboratory.…”

Mechanisms of glycine formation from aminoacetonitrile in space

“…19–21 Our recent studies include barrierless formations of protonated nucleobases starting from ion and neutral pairs detected in the ISM. 22–24 Instead of Gly, the formation of its precursors, such as Gly radical cation (Gly + ˙) or protonated Gly (GlyH + ), from formic acid (HCOOH) or acetic acid (CH 3 COOH), have been simulated. The barriers reported for the following reactions are higher than 70 kJ mol −1 : CH 3 NH 2 + ˙ + HCOOH → GlyH + + H˙, 25 CH 3 NH 3 + + HCOOH → GlyH + + H 2 , 25 NH 2 OH + ˙ + CH 3 COOH → Gly + ˙ + H 2 O, 18,26 and NH 3 OH + + CH 3 COOH → GlyH + + H 2 O.…”

“…[19][20][21] Our recent studies include barrierless formations of protonated nucleobases starting from ion and neutral pairs detected in the ISM. [22][23][24] Instead of Gly, the formation of its precursors, such as Gly radical cation (Gly + ) or protonated Gly (GlyH + ), from formic acid (HCOOH) or acetic acid (CH 3 COOH), have been simulated. The barriers reported for the following reactions are higher than 70 kJ mol…”