On the Interaction of Methyl Azide (CH3N3) Ices with Ionizing Radiation: Formation of Methanimine (CH2NH), Hydrogen Cyanide (HCN), and Hydrogen Isocyanide (HNC)

Quinto-Hernandez, Alfredo; Wodtke, Alec M.; Bennett, Christopher J.; Kim, Y. S.; Kaiser, Ralf I.

doi:10.1021/jp103028v

Cited by 25 publications

(15 citation statements)

References 70 publications

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“…With respect to the initial compound of the reaction (Figure a), although only two stables conformers are predicted by the calculations ( C s and C 1 symmetry), there are five bands in the characteristic region (2100–2200 cm −1 ), where N 3 ‐asymmetric stretching modes appear. This is a common and well‐known phenomenon that is observed in the infrared spectra of azides and it is attributed to overtone and combination modes . Therefore, the analysis of the A and B spectra corroborates that the initial compound is AZN and the final one HCN.…”

Section: Resultssupporting

confidence: 67%

Insights into the Thermal and Photochemical Reaction Mechanisms of Azidoacetonitrile. Spectroscopic and MS‐CASPT2 Calculations

Algarra

Soto

2020

ChemPhysChem

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This work studies the photochemical and thermal decompositions of azidoacetonitrile (N3CH2CN) from both the experimental and theoretical points of view. The data of the photochemical experiments are taken from the literature, while the thermal decomposition have been carried out by us. In addition, we have performed ab initio calculations of the multiconfigurational type [complete active space self‐consistent field (CASSCF) and the multistate multireference perturbation theory (MS‐CASPT2)]. It is found that the first step of both type of decompositions is N2 elimination and formation of closed shell singlet nitrene. Afterwards, the nitrene tends to rapidly rearrange into formimidoyl cyanide (HNCHCN). As both reactions progress, the imine isomerizes into formimidoyl isocyanide (HNCHNC). The photoisomerization of the imine takes places thorough a conical intersection, while the same reaction on the ground electronic state occurs via a conventional transition state. The last step of the global reaction is decomposition of the imines into HCN and CNH. In photochemical conditions, the conjunction of the imines and its dissociation products (HCN and CNH) yields adenine

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Section: Resultssupporting

confidence: 67%

Insights into the Thermal and Photochemical Reaction Mechanisms of Azidoacetonitrile. Spectroscopic and MS‐CASPT2 Calculations

Algarra

Soto

2020

ChemPhysChem

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“…Methylamine (CH 3 NH 2 ) is one of the atmospheric precursors of the greenhouse nitrous oxide (N 2 O) gas and HCN and is one of the sources of the formation of NO x [2][3][4] . For example: the synthetic nitrogen-based fuel is one the source of NO x emission 5,6 .…”

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confidence: 99%

Computational studies on the gas phase reaction of methylenimine (CH2NH) with water molecules

Ali

2020

Sci Rep

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gas phase reaction ≤ 500 K, but the rate of formation of formaldehyde and ammonia is predicted to be negligibly slow. This result is also consistent with previous studies on the similar reaction system, i.e., H 2 O + H 2 C=C=O. Experimental studies are required to understand the formation of CH 2 O and NH 3 from CH 2 NH + H 2 O, and other formation schemes must be explored. Once the laboratory characterization is complete, CH 2 O and NH 3 will be an ideal target for observational search. Although this is an interesting reaction system, our results demonstrate that CH 2 NH + H 2 O is not important under atmospheric and combustion conditions compared to an important radical molecule reaction. Such results are encouraging, and chemical kinetic mechanism can be useful for the future implementation of hydrolysis of other imine compounds.

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“…Note that lower excited states of many organic azides, which correspond to the states populated after the nonadiabatic dynamics observed here, generally have lifetimes of a few hundred femtoseconds (62)(63)(64), while the lowest excited state has a lifetime of a few to several hundred picoseconds (65)(66)(67). The asymptotic (longtime) products formed from VUV excitation of methyl azide, which occurred after the short-timescale nonadiabatic dynamics discussed here, have been explored in detail by Wodtke and coworkers (68)(69)(70)(71), including minor pathways for ion-pair formation (71) and cyclic N 3 formation (70). Indeed, very recently, detailed measurements became available of the neutral dissociation products formed after excitation at 157 nm, very close to our pump wavelength (72).…”

Section: Discussionmentioning

confidence: 64%

“…Methyl azide was prepared by established procedures (68,79), slightly modified to increase safety. It should be noted that although methyl azide is an explosive molecule, the large majority of reported accidents have been traced to either hydrazoic acid or heavy metal azide formation (80).…”

Section: Methodsmentioning

confidence: 99%

Ultrafast 25-fs relaxation in highly excited states of methyl azide mediated by strong nonadiabatic coupling

Peters

Couch

Mignolet

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Highly excited electronic states are challenging to explore experimentally and theoretically-due to the large density of states and the fact that small structural changes lead to large changes in electronic character with associated strong nonadiabatic dynamics. They can play a key role in astrophysical and ionospheric chemistry, as well as the detonation chemistry of high-energy density materials. Here, we implement ultrafast vacuum-UV (VUV)-driven electron-ion coincidence imaging spectroscopy to directly probe the reaction pathways of highly excited states of energetic molecules-in this case, methyl azide. Our data, combined with advanced theoretical simulations, show that photoexcitation of methyl azide by a 10-fs UV pulse at 8 eV drives fast structural changes and strong nonadiabatic coupling that leads to relaxation to other excited states on a surprisingly fast timescale of 25 fs. This ultrafast relaxation differs from dynamics occurring on lower excited states, where the timescale required for the wavepacket to reach a region of strong nonadiabatic coupling is typically much longer. Moreover, our theoretical calculations show that ultrafast relaxation of the wavepacket to a lower excited state occurs along one of the conical intersection seams before reaching the minimum energy conical intersection. These findings are important for understanding the unique strongly coupled non-Born-Oppenheimer molecular dynamics of VUV-excited energetic molecules. Although such observations have been predicted for many years, this study represents one of the few where such strongly coupled non-Born-Oppenheimer molecular dynamics of VUV-excited energetic molecules have been conclusively observed directly, making it possible to identify the ultrafast reaction pathways.

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On the Interaction of Methyl Azide (CH₃N₃) Ices with Ionizing Radiation: Formation of Methanimine (CH₂NH), Hydrogen Cyanide (HCN), and Hydrogen Isocyanide (HNC)

Cited by 25 publications

References 70 publications

Insights into the Thermal and Photochemical Reaction Mechanisms of Azidoacetonitrile. Spectroscopic and MS‐CASPT2 Calculations

Insights into the Thermal and Photochemical Reaction Mechanisms of Azidoacetonitrile. Spectroscopic and MS‐CASPT2 Calculations

Computational studies on the gas phase reaction of methylenimine (CH2NH) with water molecules

Ultrafast 25-fs relaxation in highly excited states of methyl azide mediated by strong nonadiabatic coupling

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