Automated reaction mechanisms and kinetics based transition state search process AMK-gau_xtb and its application to the substitution reaction of the nitroso group in 2,4,6-trinitrotoluene by hydroxide anion in the aqueous phase

Liang

et al. 2022

J Comput Chem

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To improve the transition state (TS) search capability in complex chemical environments, AMK_Mountain is constructed based on the automated reaction mechanisms and kinetics (AutoMeKin) package. AMK_Mountain does not distinguish the reaction type of the TSs, which is beneficial to obtaining a more comprehensive reaction mechanism. In this study, the first step of the alkaline hydrolysis process of nitrocellulose monomer was adopted as the research object, and 730 possible initial configurations are constructed and 22 TSs pass high‐level calculations. Energy difference and interaction region indicator reveal that the first step of alkaline hydrolysis is mainly the combination of nitrogen‐containing functional groups at the positions α and β with hydroxide anions, followed by the formation of nitric acid and the further loss of protons to form nitrate. Overall, in combination with GFN2‐xTB and ORCA, the AMK_Mountain technique provides a reliable method for the location of the TSs in complex environments.

Section: Introductionmentioning

confidence: 86%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 97%

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Automated reaction mechanisms and kinetics with the nudged elastic band method‐based AMK_Mountain and its description of the preliminary alkaline hydrolysis of nitrocellulose monomer

Liang

et al. 2022

J Comput Chem

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“…Under the guidance of this thought, thanks to the high-precision semiempirical method GFN n -xTB developed by Grimme, especially GFN 2 -xTB, qualitative MD and low-level operations have been rapidly improved in accuracy and speed. Furthermore, GFN 2 -xTB is also the basis for the successful development of the new processes AMK-gau_xtb and AMK_Mountain . Among them, AMK_Mountain based only on ORCA5.0 − has been applied to the first step of the alkaline hydrolysis reaction of the NC monomer and has brought a new understanding of the reaction pathway to generate nitrate anions and nitrite anions.…”

Section: Introductionmentioning

confidence: 99%

Heuristic-Based Alkaline Hydrolysis Mechanism of Nitrate Ester (Nitrocellulose Monomer) and Nitroamine (Hexogen) Compounds: Electrostatic Attraction Effect of the Nitro Group

Liang

et al. 2023

J. Phys. Chem. A

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The alkaline hydrolysis reaction of energetic materials is important and complex. With improved performance, AMK_Mountain was used to systematically study the alkaline hydrolysis of the nitrocellulose monomer and hexogen. The reaction pathways showed that the nitrocellulose monomer produces the nitrate anion and nitrite anion differently, while hexogen only produces the nitrite anion. Electronic structure results at the M06-2X/6-311G(d,p)/PCM(Pauling) level showed that the nitrocellulose monomer and hexogen have a similar pathway in their main energy-releasing process (nitrite anion production): with electrostatic attraction effects after proton transfer, the nitrite anion dissociates from the original structure with a low barrier. Moreover, during the alkaline hydrolysis of the nitrocellulose monomer, the metastable intermediates after proton transfer may be directly generated following transition states that, structurally, tend to produce nitrite anions “proximal” to the proton transfer site and produce nitrate anions “distal” to the proton transfer site. Electronic structure analysis showed that representative metastable intermediates revealed that the charge transfer caused by electrostatic attraction may be the direct cause of these reactions.

Research on the reaction mechanism of 2,4,6‐trinitrotoluene resource utilization I: Formation of 2,4,6‐trinitrobenzoic acid in acetic acid with N,N′,N″‐trihydroxyisocyanuric acid catalyst

J of Physical Organic Chem

Liu

2023

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As an organic molecule catalyst, N,N',N"‐trihydroxyisocyanuric acid can selectively catalyze the oxidation of the methyl group of waste 2,4,6‐trinitrotoluene to generate 2,4,6‐trinitrobenzoic acid. This reaction can avoid environmental pollution by inorganic heavy metal catalysts. In this study, four reaction stages of this catalytic reaction were designed and validated computationally at the M06‐2X‐D3ZERO/6‐311G(d,p) level using the acetic acid solvent model. These validations include transition state searches, intrinsic reaction coordinate calculations, reactant and product optimizations, and frequency calculations. The final reaction network of 23 transition states shows that after N,N',N"‐trihydroxyisocyanuric acid activation and common reaction, the network bifurcates into two stages: alcohol to carboxylic acid and aldehyde to carboxylic acid. Although the former stage releases about 155 kcal/mol of Gibbs free energy, less than the 177 kcal/mol from the latter stage, the overall reaction equation shows that the pathway including former stage does not consume the catalytically active substance IM_T2, which saves the energy required for reactivation and is thus more favorable. Furthermore, the key transition states in the reaction network include bimolecular substitution reactions and proton hopping transfer reactions. Analyses of their interaction region indicators and intrinsic reaction coordinate results demonstrate strong selectivity. Additionally, the energy barriers and heat releases of the latter are twice and 1.3 times greater than those of the former, respectively. In summary, this study elucidated two competitive reaction pathways and identified the more energetically favorable and selective pathway, it provides useful insights for further optimization of industrial utilization of 2,4,6‐trinitrotoluene.