Few experimental studies on the CH + CO2 global reaction propose H, CO, and HCO as major products. However, the reaction mechanisms behind this process have not yet been elucidated. Moreover, some intriguing kinetic particularities were noticed in these previous investigations. The advanced theoretical study performed here shows that a CH insertion mechanism is capable of explaining all the experimental data available. Hence, the strong deviations from a traditional Arrhenius behavior ascribed to the rate-determining elementary reaction (the CH insertion step) account for the kinetic particularities observed experimentally. A change in the preferred product channel as temperatures increase (from HCO + CO to H + 2CO) is also predicted to occur due to the HCO decomposition, although the CH depletion rates in typical conditions are not affected by this additional step.

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The forward and reverse H2O + CO ↔ HCOOH reactions were investigated using high‐level methodologies in order to provide accurate thermodynamic and kinetic data between 200 and 4000 K. Geometries of reactants, transition state (TS), and product were determined with the Coupled Cluster Theory including single and double excitations (CCSD) along with the cc‐pVTZ basis set, whereas associated vibrational frequencies, zero‐point energies, and thermal corrections were scaled to consider anharmonicity effects. Besides, the description of electronic energies was improved by means of core‐valence correlation and iterative triple‐excitation contributions together with a complete basis set extrapolation (ECBS,Δ) in order to achieve accurate values of enthalpies, Gibbs energies, and rate constants. Such rate constants were estimated at the high‐pressure limit by variational TS treatments combined with different quantum tunneling approaches. Finally, modified Arrhenius’ equations were fitted between 700 and 4000 K from our most reliable results.

Rate coefficients for the radiative association of titanium and oxygen atoms to form the titanium monoxide (TiO) molecule are estimated. The radiative association of Ti(3F) and O(3P) atoms is dominated by an approach along the C3Δ potential energy curve, accompanied by spontaneous emission into the X3Δ ground state of TiO. For temperatures ranging from 300–14 000 K, the total rate coefficients are found to vary from 4.76 × 10−17 to 9.96 × 10−17 cm3 s−1, respectively.

The forward and reverse H2O + HCN ↔ HCONH2 global reactions were studied along temperatures from 200 to 4000 K. Equilibrium geometries and vibrational frequencies were obtained from calculations at the Coupled Cluster theory with single and double excitations (CCSD)/cc-pVDZ level; whereas enthalpies, Gibbs energies, and thermal rate constants were achieved by means of the CCSD(T)/CBS//CCSD/cc-pVDZ combined treatment. The estimates performed considering physical and chemical conditions proposed for the primitive atmosphere of Earth indicate that the formamide concentration might be 3.0–4.4 times larger than the one for HCN at 700 K, suggesting that this forward gas phase reaction could provide an efficient production route for formamide during an age just before the formation of early oceans. This route is also considerably fast once the chemical equilibrium is attained in some decades at this temperature. In short, our research reinforces that more complex organic compounds, such as formamide, could be synthetized in the Earth’s primordial atmosphere, even considering a neutral atmosphere scenario composed mainly by H2O, CO2, and some N2.