Hydrogen Abstraction/Addition Tunneling Reactions Elucidate the Interstellar H<sub>2</sub>NCHO/HNCO Ratio and H<sub>2</sub> Formation

Haupa, Karolina Anna; Tarczay, György; Lee, Yuan‐Pern

doi:10.1021/jacs.9b04491

Cited by 74 publications

(104 citation statements)

References 46 publications

(72 reference statements)

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“…In order to demonstrate the applicability of this method, we briefly discuss the H abstraction and addition reactions of formamide (H 2 NCHO) and isocyanic acid (HNCO) in solid para-H 2 . (See details of this investigation in Haupa et al (2019)). H 2 NCHO, the smallest molecule possessing an amide group, was first detected toward Sagittarius B2 almost 50 years ago (Rubin et al (1971)).…”

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confidence: 99%

On the correlation of the abundances of HNCO and NH₂CHO: Advantages of solid para-H₂ to study astrochemical H-atom addition and abstraction reactions

2019

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In dense interstellar clouds that are shielded from high-energy radiation (e.g., UV photons or cosmic rays), H-atom addition and abstraction reactions that take place on grain surfaces play principal roles in the synthesis or decomposition of complex organic molecules (COMs). These reactions are extensively investigated with laboratory experiments by bombarding astrophysical analogue ices with a beam of low-temperature H atoms. Here we demonstrate that, although 2-4 K solid para-H2 does not represent a typical environment of the surface of interstellar grains, para-H2 matrix isolation combined with IR spectroscopy is a complementary tool to sensitively detect astrochemical hydrogenation and dehydrogenation processes.

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confidence: 99%

On the correlation of the abundances of HNCO and NH₂CHO: Advantages of solid para-H₂ to study astrochemical H-atom addition and abstraction reactions

2019

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“…It has been used in the study of the formation of urea in irradiation studies, where its irradiation is shown to lead to the formation of formamide and urea (Ferus et al 2018;Raunier et al 2003Raunier et al , 2004. In addition, it has been shown to be a product of the dissociation of formamide and has even been suggested to be a catalyst for the formation of H 2 in the ISM (Lundell, Krajewska & Räsänen 1998;Duvernay et al 2005;Haupa, Tarczay & Lee 2019). Moreover, there is a clear correlation with the abundances of formamide (Bisschop et al 2007;López-Sepulcre et al 2015).…”

Section: Charged Pathwaymentioning

confidence: 99%

Computational studies into urea formation in the interstellar medium

Slate

Barker

Euesden

et al. 2020

Monthly Notices of the Royal Astronomical Society

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Formation routes involving closed shell, radical and charged species, for urea have been studied using computational methods to probe their feasibility in the ISM. All reactions involving closed shell species were found to have prohibitive barriers. The radical-radical reaction possesses a barrier of only 4 kJ mol−1 which could be surmountable. A charged species based route was also investigated. A barrier of only 8 kJ mol−1 was found in that case, when a partial water ice shell was included.

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“…[17][18][19][20][21] Many combustion processes are also related to the HNCO species and its derivatives. 7,[22][23][24] Isocyanate molecules are also important interstellar species [4][5][6]25 that are implicated as critical intermediates for prebiotic precursors such as formamide, [26][27][28] thyamine, 29 and urea. 30 One of the reasons isocyanates are so ubiquitous is their diverse and facile reactivity with many organic molecules, 11,17,[31][32][33]33 thus motivating further research into understanding the important features of reactions involving isocyanates.…”

Section: Introductionmentioning

confidence: 99%

Catalyzed Reaction of Isocyanates (RNCO) with Water

Wolf¹,

Vandezande

Schaefer³

2021

Preprint

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The reactions between substituted isocyanates (RNCO) and other small molecules (e.g. water, alcohols, and amines) are of significant industrial importance, particularly for the development of novel polyurethanes and other useful polymers. We present very high level ab initio computations on the HNCO + H 2 O reaction, with results targeting the CCSDT(Q)/CBS//CCSD(T)/cc-pVQZ level of theory. Our results affirm that hydrolysis can occur across both the N− −C and C− −O bonds of HNCO via concerted mechanisms to form carbamate or imidic acid with ∆H 0K barrier heights of 38.5 and 47.5 kcal mol −1 . A total of 24 substituted RNCO + H 2 O reactions were studied.Geometries obtained with a composite method and refined with CCSD(T)/CBS single point energies determine that substituted RNCO species have a significant influence on these barrier heights, with an extreme case like fluorine lowering both barriers by close to 20 kcal mol −1 and most common alkyl substituents lowering both by approximately 4 kcal mol −1 . Natural Bond Oribtal (NBO) analysis provides evidence that the 1 predicted barrier heights are strongly associated with the occupation of the in-plane C−O* orbital of the RNCO reactant. Key autocatalytic mechanisms are considered in the presence of excess water and RNCO species. Additional waters (one or two) are predicted to lower both barriers significantly at the CCSD(T)/aug-cc-pV(T+d)Z level of theory with strongly electron withdrawing RNCO substituents also increasing these effects, similar to the uncatalyzed case. The 298 K Gibbs energies are only marginally lowered by a second catalyst water molecule, indicating that the decreasing ∆H 0K barriers are offset by loss of translational entropy with more than one catalyst water. Two-step 2 RNCO + H 2 O mechanisms are characterized for the formation of carbamate and imidic acid. The second step of these two pathways exhibits the largest barrier and presents no clear pattern with respect to substituent choice. Our results indicate that an additional RNCO molecule might catalyze imidic acid formation but have less influence on the efficiency of carbamate formation. We expect that these results lay a firm foundation for the experimental study of substituted isocyanates and their relationship to the energetic pathways of related systems.

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Hydrogen Abstraction/Addition Tunneling Reactions Elucidate the Interstellar H₂NCHO/HNCO Ratio and H₂ Formation

Cited by 74 publications

References 46 publications

On the correlation of the abundances of HNCO and NH₂CHO: Advantages of solid para-H₂ to study astrochemical H-atom addition and abstraction reactions

On the correlation of the abundances of HNCO and NH₂CHO: Advantages of solid para-H₂ to study astrochemical H-atom addition and abstraction reactions

Computational studies into urea formation in the interstellar medium

Catalyzed Reaction of Isocyanates (RNCO) with Water

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Hydrogen Abstraction/Addition Tunneling Reactions Elucidate the Interstellar H2NCHO/HNCO Ratio and H2 Formation

Cited by 74 publications

References 46 publications

On the correlation of the abundances of HNCO and NH2CHO: Advantages of solid para-H2 to study astrochemical H-atom addition and abstraction reactions

On the correlation of the abundances of HNCO and NH2CHO: Advantages of solid para-H2 to study astrochemical H-atom addition and abstraction reactions

Computational studies into urea formation in the interstellar medium

Catalyzed Reaction of Isocyanates (RNCO) with Water

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Hydrogen Abstraction/Addition Tunneling Reactions Elucidate the Interstellar H₂NCHO/HNCO Ratio and H₂ Formation

On the correlation of the abundances of HNCO and NH₂CHO: Advantages of solid para-H₂ to study astrochemical H-atom addition and abstraction reactions

On the correlation of the abundances of HNCO and NH₂CHO: Advantages of solid para-H₂ to study astrochemical H-atom addition and abstraction reactions