Some Insights Into Formamide Formation Through Gas-Phase Reactions in the Interstellar Medium

Abstract

We study the viability of different gas-phase ion-molecule reactions that could produce precursors of formamide in the interstellar medium. We analyze different reactions between cations containing a nitrogen atom (NH + 3 , NH + 4 , NH 3 OH + , and NH 2 OH + ) and neutral molecules having one carbonyl group (H 2 CO and HCOOH). First, we report a theoretical estimation of the reaction enthalpies for the proposed processes. Second, for more favorable reactions, from a thermodynamic point of view, we perform a theoretical study of the potential energy surface. In particular, the more exothermic processes correspond to the reactions of ionized and protonated hydroxylamine with formaldehyde. In addition, a neutral-neutral reaction has also been considered. The analysis of the potential energy surfaces corresponding to these reactions shows that these processes present a net activation barrier and that they cannot be considered as a source of formamide in space.

Synthesis of Formamide and Related Organic Species in the Interstellar Medium via Chemical Dynamics Simulations

“…The other isomer, NH 2 OH + 2 , is much more reactive, as already pointed out in static calculations (Redondo et al 2014a). Our dynamics show that four products are obtained: two proton transfers, loss of water, and formation of NH 2 OCH + 2 , which is an isomeric form of protonated formamide.…”

“…More recently, it has also been detected in the solar-type protostar IRAS 16293-2422 (Kahane et al 2013). A recent study of Redondo et al (2014a) has shown that the ion/ molecule reaction involving NH 2 OH + 2 and H 2 CO may be the basis of the formation of this molecule, while other authors have suggested that it may be obtained by a ion-molecule reaction involving H 2 CO and NH + 4 followed by dissociative electron recombination (Quan & Herbst 2007;Halfen et al 2011). Other studies have proposed neutral/neutral reactions, like those between HCOOH or H 2 CO with NH 3 both in the gas phase and on ice of interstellar grains (Woon 2001a(Woon , 2001b.…”

“…It is not surprising that NH 3 OH + is not reactive, since it is the most stable isomer. The PES study of Largo and co-workers has already pointed out that it is unlikely that NH 3 OH + will react to produce formamide (Redondo et al 2014a). Thus, if we assume that this isomer is formed in the ISM, the only expected reaction in the presence of H 2 CO is proton transfer and thus the formation of neutral NH 2 OH and the H 2 COH + ion.…”

“…Here, we focus our attention on the simplest ion-molecule reactions between NH 2 OH/H 2 CO and NH 3 /H 2 CO considering every possible protonated/neutral couple, stimulated by the aforementioned works, which suggested that these reactants may be the precursor for formamide synthesis in the ISM (Quan & Herbst 2007;Halfen et al 2011;Redondo et al 2014a). In particular, simulations may be seen as theoretical laboratories in which one can perform reactions and analyze results at a relatively low cost.…”

Shedding light on the formation of the pre-biotic molecule formamide with ASAI

“…However, as recently mentioned by Redondo et al (2014), it presents a net activation barrier of > 1000 K that makes it inviable in interstellar conditions. Other neutral-neutral reactions evaluated by these authors also revealed to have large activation barriers, thus ruling them out as dominant or efficient mechanisms to produce NH2CHO.…”