Table 2
Summary of the reactions studied in this work, organised according to the binding mode of •CN on either water or carbon monoxide.
| Hemibonded •CN on H2O | |||||
|---|---|---|---|---|---|
| Reaction | Product | Barrier | Reaction energy | Trans. freq. | Crossover temp. |
| •CH3 + •CNhemi | CH3CN | 2.8 | −495.1 | 117 | − |
| •CH3 + •CNhemi | CH3NC | 3.1δ | −355.7δ | 100 | − |
| •CNhemi+2H2O | t-HO•CNHwHt(2) | 51.6 | −120.1 | 592 | 135 |
| •CNhemi+ 3H2O | c-HO• CNHwHt(3) | 34.1 | −84.6 | 310 | 71 |
| •CNhemi+4H2O | t-HO•CNHwHt(4) | 20.7 | −109.4 | 550 | 126 |
| •CH3 + t-HO•CNHwHt(2) | CH3COHNH | 2.1α | −372.8α | – | – |
| •CH3 + c-HO•CNHwHt(3) | CH3COHNH | 1.2α | −389.8α | – | – |
| •CH3 + t-HO•CNHwHt(4) | CH3COHNH | 3.1β | −351.8β | – | – |
| •CH3 diffusion (averaged values) | |||||
| Reaction | Product | Barrier | Reaction energy | Trans. freq. | Crossover temp. |
| [ineq] | – | 2.3 | 1.0 | – | – |
| [ineq] | – | 3.2 | 0.2 | – | – |
| Water-catalysed Acetimidic acid-Acetamide conversion | |||||
| Reaction | Product | Barrier | Reaction energy | Trans. freq. | Crossover temp. |
| AAc → Am(BS1) | CH3C(O)NH2 | 58.1 | −44.9 | 255 | 58 |
| AAc → Am (BS2) | CH3C(O)NH2 | 20.0 | −61.2 | 584 | 134 |
| Formation of cyanic (HOCN) and isocyanic acid (HNCO) on water ices | |||||
| Reaction | Product | Barrier | Reaction energy | Trans. freq. | Crossover temp. |
| [ineq] | HOCN + CH4 | 23.3 | −303.1 | 2029 | 464 |
| t-HO•CNHwHt(4) + •CH3 | HNCO + CH4 | 33.2 | −384.9 | 3237 | 741 |
| t-HO•CNHwHt(4) + •H | HOCN + H2 | 6.0 | −310.7 | 1504 | 344 |
| t-HO•CNHwHt(4) + •H | HNCO + H2 | 23.9 | −398.9 | 3204 | 734 |
| H-bonded •CN on H2O | |||||
| Reaction | Product | Barrier | Reaction energy | Trans. freq. | Crossover temp. |
| •CH3 + •CNε | CH3CN | Barrierless | −532.9 | – | – |
| •CH3 + •CN | CH3NC | No reaction | – | – | – |
| •CN van der Waals bonded on CO | |||||
| Reaction | Product | Barrier | Reaction energy | Trans. freq. | Crossover temp. |
| CH3 + CNε | CH3CN | Barrierless | −524.0 | – | – |
| CH3 + CNε | CH3NC | Barrierless | −422.4 | – | – |
| Covalently bound NC•CO | |||||
| Reaction | Product | Barrier | Reaction energy | Trans. freq. | Crossover temp. |
| •CH3 + NC•CO | CH3C(O)CN | Barrierless | −493.4 | – | – |
Notes. Energy units are in kJ mol−1. The terms are as follows: wHt stands for ‘water-assisted H transfer’, AAc stands for acetimidic acid (CH3COHNH), and Am is for acetamide (CH3CONH2). Raw energetics and extra data can be found in Sect. D of the appendix. (α)Energy relative to the intermediate (i.e. the product of the first reaction step, wHt(2,3)). (β)Energy relative to a manually built intermediate with an energy relative to the products (wHt(4)) of the first step of − 6.4 kJ mol−1. (γ)Reactants’ structure prepared manually (see Figure 3). (ε)Reactants’ geometry was prepared by putting •CH3 far from •CN. (δ)Energetics calculated at RSCAN-D3(BJ) level (see Sect. 2).
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