Formation of Formamide from HCN + H₂O: A Computational Study on the Roles of a Second H₂O as a Catalyst, as a Spectator, and as a Reactant

Abstract

Formamide (NH 2 CHO), being the smallest and fundamental building block of life (with a peptide linkage), has recently been able to attract much interests, in the field of astrochemistry, astrophysics, and astrobiology. In this work, using quantum mechanical computations, reactions between HCN and H 2 O, leading to the formation of formamide, have been analyzed. For the first time, an alternative and competing reaction channel, which proceeds via a geminal diol intermediate, for the formation of formamide, has been proposed. In this alternative channel, an extra water molecule (second H 2 O) was found to be acting as a reactant, in the second step of the reaction path. Effects of second H 2 O molecule in the reaction paths, providing catalytic assistance to the reaction or behaving like a spectator (concept is introduced for the first time for this reaction), have also been analyzed. Usefulness of spectator behavior is highlighted for the reactions happening on the rigid water-ice surfaces, where the water-ice may not be getting involved for any catalytic assistance. In light of catalytic assistances provided by the second H 2 O, prominent effects in reducing the barrier heights drastically (even for the second step of the reaction, the barrier height was found to be below the reactants), through a hydrogen relay transport mechanism, were observed. In addition to the mechanism studies, interstellar feasibilities of all the reaction channels and their significances are discussed in detail.

C2H5NO Isomers: from Acetamide to1,2-Oxazetidine and Beyond

“…The auto-catalytic nature of this reaction is a point in its favour as well as the fact that the more direct addition R -C ---N H2O −−→ RC(OH) --NH has been discounted. 93,94 Since this system exhibits quite a range of bonding, even within the restrictive context of neutral and closed-shell molecules, the results are likely to be useful for incorporation into databases for artificial intelligence learning/predictive efforts -ameliorating the well-known problem of dataset bias.…”

“…to form firstly methanimidic acid, HC(OH) --NH, and then formamide, HC(O) -NH 2 , has been shown not to be competitive, despite the cooperation of additional water molecules, due to a high energy barrier byRimola et al in theoretical calculations of this reaction on a 33-H 2 O ice cluster model 93. A view reinforced by Darla et al in ωB97xD/aug-ccpVTZ gas-phase calculations in which they show that neither the presence of an additional water molecule as a participant or as a spectator makes a sufficient reduction in the barriers to reaction to render the process kinetically significant 94. Woon has shown in density functional calculations of a cluster of 24 water molecules that C + ( 2 P) reacts with H -C ---N to form a transient species H -C --N -C + firstly, which then reacts with a neighbouring H 2 O to form H -C(OH 2 ) --N -C + which then loses a proton from the O-atom to a water molecule forming, H -C(OH) --NC + H 3 O + -"the entire process has no activation barriers whatsoever" 95.…”

Prebiotic Organic Chemistry of Formamide and the Origin of Life in Planetary Conditions: What We Know and What Is the Future

“…HCN and HCONH 2 are both effective substrates in MCRs. They are easily transformed into reactive intermediates that react combinatorially [21]. HCONH 2 is liquid between 6 • C and 210 • C and has a high dielectric constant, which makes it a solvent for polar biomolecules, favoring successive oligomerization [22].…”

C2H5NO Isomers: from Acetamide to1,2-Oxazetidine and Beyond

“…The auto-catalytic nature of this reaction is a point in its favour as well as the fact that the more direct addition R -C ---N H2O −−→ RC(OH) --NH has been discounted. 97,98 Since this system exhibits quite a range of bonding, even within the restrictive context of neutral and closed-shell molecules, the results are likely to be useful for incorporation into databases for artificial intelligence learning/predictive efforts -ameliorating the well-known problem of dataset bias.…”

“…to form firstly methanimidic acid, HC(OH) --NH, and then formamide, HC(O) -NH 2 , has been shown not to be competitive, despite the cooperation of additional water molecules, due to a high energy barrier byRimola et al in theoretical calculations of this reaction on a 33-H 2 O ice cluster model 97. A view reinforced by Darla et al in ωB97xD/aug-ccpVTZ gas-phase calculations in which they show that neither the presence of an additional water molecule as a participant or as a spectator makes a sufficient reduction in the barriers to reaction to render the process kinetically significant 98. Woon has shown in density functional calculations of a cluster of 24 water molecules that C + ( 2 P) reacts with H -C ---N to form a transient species H -C --N -C + firstly, which then reacts with a neighbouring H 2 O to form H -C(OH 2 ) --N -C + which then loses a proton from the O-atom to a water molecule forming, H -C(OH) --NC + H 3 O + -"the entire process has no activation barriers whatsoever" 99.…”