Theoretical studies and topological analysis of the electron density of clusters of O3 with HNCO and HCNO

Zabardasti, Abedien; Kakanejadifard, Ali; Kikhaei, Mozhgan; Solimannejad, Mohammad

doi:10.1016/j.theochem.2010.08.015

Cited by 10 publications

(7 citation statements)

References 28 publications

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“…The potential energy surfaces of the initiation reactions of all four reaction systems were characterized at the M06-2X/aug-cc-pVTZ level of theory (Dunning, 1989;Zhao and Truhlar, 2008), optimizing the geometries and rovibrational characteristics of all minima and transition states. The relative energy of the critical points was further refined at the CCSD(T) level of theory in a set of single-point energy calculations using a systematic series of basis sets, aug-cc-pVxZ (x = D, T , Q) (Dunning, 1989;Purvis and Bartlett, 1982).…”

Section: Theoretical Methodologiesmentioning

confidence: 99%

Atmospheric chemical loss processes of isocyanic acid (HNCO): a combined theoretical kinetic and global modelling study

Rosanka

Nguyen

et al. 2020

Atmos. Chem. Phys.

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Abstract. Isocyanic acid (HNCO) is a chemical constituent suspected to be harmful to humans if ambient concentrations exceed ∼1 ppbv. HNCO is mainly emitted by combustion processes but is also inadvertently released by NOx mitigation measures in flue gas treatments. With increasing biomass burning and more widespread usage of catalytic converters in car engines, good prediction of HNCO atmospheric levels with global models is desirable. Little is known directly about the chemical loss processes of HNCO, which limits the implementation in global Earth system models. This study aims to close this knowledge gap by combining a theoretical kinetic study on the major oxidants reacting with HNCO with a global modelling study. The potential energy surfaces of the reactions of HNCO with OH and NO3 radicals, Cl atoms, and ozone were studied using high-level CCSD(T)/CBS(DTQ)//M06-2X/aug-cc-pVTZ quantum chemical methodologies, followed by transition state theory (TST) theoretical kinetic predictions of the rate coefficients at temperatures of 200–3000 K. It was found that the reactions are all slow in atmospheric conditions, with k(300K)≤7×10-16 cm3molecule-1s-1, and that product formation occurs predominantly by H abstraction; the predictions are in good agreement with earlier experimental work, where available. The reverse reactions of NCO radicals with H2O, HNO3, and HCl, of importance mostly in combustion, were also examined briefly. The findings are implemented into the atmospheric model EMAC (ECHAM/MESSy Atmospheric Chemistry) to estimate the importance of each chemical loss process on a global scale. The EMAC predictions confirm that the gas-phase chemical loss of HNCO is a negligible process, contributing less than 1 % and leaving heterogeneous losses as the major sinks. The removal of HNCO by clouds and precipitation contributes about 10 % of the total loss, while globally dry deposition is the main sink, accounting for ∼90 %. The global simulation also shows that due to its long chemical lifetime in the free troposphere, HNCO can be efficiently transported into the UTLS by deep convection events. Daily-average mixing ratios of ground-level HNCO are found to regularly exceed 1 ppbv in regions dominated by biomass burning events, but rarely exceed levels above 10 ppt in other areas of the troposphere, though locally instantaneous toxic levels are expected.

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Section: Theoretical Methodologiesmentioning

confidence: 99%

Atmospheric chemical loss processes of isocyanic acid (HNCO): a combined theoretical kinetic and global modelling study

Rosanka

Nguyen

et al. 2020

Atmos. Chem. Phys.

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“…While little is known about C 4 H 4 NO, there do exist some relevant studies of isocyanic acid. Zabardasti et al 2 . report from theoretical studies that HNCO forms H‐bonded complexes with O 3 and that these are relatively stable in the gas phase at room temperature.…”

Section: Introductionmentioning

confidence: 99%

Computational study of the reaction of C₃H₃ with HNCO and the decomposition of C₄H₄NO radicals

Nguyễn

Trang

Nguyen

et al. 2022

Int J of Chemical Kinetics

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Ab initio CCSD(T)/CBS(T,Q,5)//M06-2X/aug-cc-pVTZ calculations have been applied to figure out the C 4 H 4 NO (isopropyl aminocarbonyl) potential energy surface (PES). The resulting energetics and molecular parameters of all species involved in the system have been then employed in the TST and RRKM/ME computations of temperature-and pressure-dependent rate coefficients and product yields. The calculated results show that rate constants of the abstraction reactions C 3 H 3 + HNCO → C 3 H 4 + NCO are pressure-independent while those of the addition reactions C 3 H 3 + HNCO and the C 4 H 4 NO decomposition reactions were found to be pressure-dependent. The calculated enthalpies of formation for species involved in the system are in good ageement with the available literature data. All the results of this work may provide a useful database source for the further study of this kind of reactions.

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“… 2 , 3 It can bond with other substances forming H-bonded polymers which are relatively well constructed in the gas-phase environment at room temperature. 4 , 5 Due to the high toxicity of HNCO, it is implicated in causing adverse effects on human health (i.e., cataract, cardiovascular diseases, and rheumatoid arthritis) via a protein carbamylation process if its concentration in air exceeds 1 part per billion by volume. 2 , 6 , 7 The main source of HNCO emission into the atmosphere is from combustion processes derived from not only natural but also anthropogenic activities.…”

Section: Introductionmentioning

confidence: 99%

Gas Phase Reaction of Isocyanic Acid: Kinetics, Mechanisms, and Formation of Isopropyl Aminocarbonyl

Pham

Tran

2021

ACS Omega

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Isocyanic acid, HNCO, mainly emitted by combustion processes, is doubted to be detrimental to human health if its concentration surpasses ∼1 ppbv. Very little information has been found regarding the HNCO loss in the gas phase. This study aims to close this knowledge gap by performing a theoretical kinetic study on the reaction of HNCO with the propargyl radical. The potential energy surface of the HNCO + C 3 H 3 reaction was characterized utilizing high-level CCSD(T)/CBS(TQ5)//B3LYP/6-311++G(3df,2p) quantum-chemical approaches, followed by TST and RRKM/ME kinetic computations. The obtained results reveal that the reaction can proceed via H-abstraction, leading to the C 3 H 4 + NCO bimolecular products with energy barriers of 23–25 kcal/mol, and/or addition, resulting in C 4 H 4 NO intermediates with 23–26 kcal/mol barrier heights. The C 4 H 4 NO adducts when formed can decompose to products and/or return to HNCO + C 3 H 3 in which the reverse decompositions are found to be dominant with a branching ratio that accounts for nearly 100% at 300 K and 760 Torr. The calculated P -independent rate coefficients indicate that at low temperatures, the H-abstraction channels are insignificant. However, at high temperatures ( T > 1500 K), the H-abstraction path leading to H 3 CCCH + NCO prevails with a branching ratio of ∼50–53% in the descending 1800–1500 K temperature range at 760 Torr, while the H-abstraction leading to H 2 CCCH 2 + NCO is favorable at T > 1800 K, with the yield reaching above 50% at 760 Torr. In contrast to the H-abstraction rate constants, the calculated values for the additions and the C 4 H 4 NO decompositions show a positive pressure dependence. Both the total rate constants for the reactions HNCO + C 3 H 3 → products and C 4 H 4 NO → products, which are, respectively, k _total_bimo ( T ) = 3.53 × 10 –23 T 3.27 exp[(−21.35 ± 0.06 kcal/mol)/RT] cm 3 molecule –1 s –1 and k _total_uni ( T ) = 1.13 × 10 25 T –4.02 exp[(−11.77 ± 0.16 kcal/mol)/RT] s –1 , increase with the increasing temperature in the 300–2000 K range at 760 Torr. The rate constant of HNCO + C 3 H 3 → products is about 8 orders of magnitude smaller than the value of HCHO + C ...

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Theoretical studies and topological analysis of the electron density of clusters of O3 with HNCO and HCNO

Cited by 10 publications

References 28 publications

Atmospheric chemical loss processes of isocyanic acid (HNCO): a combined theoretical kinetic and global modelling study

Atmospheric chemical loss processes of isocyanic acid (HNCO): a combined theoretical kinetic and global modelling study

Computational study of the reaction of C₃H₃ with HNCO and the decomposition of C₄H₄NO radicals

Gas Phase Reaction of Isocyanic Acid: Kinetics, Mechanisms, and Formation of Isopropyl Aminocarbonyl

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Theoretical studies and topological analysis of the electron density of clusters of O3 with HNCO and HCNO

Cited by 10 publications

References 28 publications

Atmospheric chemical loss processes of isocyanic acid (HNCO): a combined theoretical kinetic and global modelling study

Atmospheric chemical loss processes of isocyanic acid (HNCO): a combined theoretical kinetic and global modelling study

Computational study of the reaction of C3H3 with HNCO and the decomposition of C4H4NO radicals

Gas Phase Reaction of Isocyanic Acid: Kinetics, Mechanisms, and Formation of Isopropyl Aminocarbonyl

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Computational study of the reaction of C₃H₃ with HNCO and the decomposition of C₄H₄NO radicals