Stability of hydroxylamine isomers in aqueous solution: Ab initio study using continuum, cluster-continuum and Shells Theory of Solvation

Lima, Guilherme Ferreira de; Pliego, Josefredo R.; Duarte, Hélio A.

doi:10.1016/j.cplett.2011.11.001

Cited by 16 publications

(23 citation statements)

References 37 publications

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“…For example, in the study of the solvation of small ions, 500 snapshots were selected for the ensemble average. Despite this high computational cost, it was successfully applied in the study of the hydroxylamine isomerization equilibrium in aqueous solution . In this case, a cubic box with 32 water molecules and the hydroxylamine were studied by molecular dynamics simulation using the DFTB method and periodic boundary conditions.…”

Section: Theorymentioning

confidence: 99%

Hybrid discrete‐continuum solvation methods

Pliego

Riveros

2019

WIREs Comput Mol Sci

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Hybrid discrete‐continuum approaches for solvation have been widely applied for diverse problems in chemistry suck as pKa calculation in aqueous and nonaqueous solvents, activation free energy barriers for ionic processes in solution, and surface reactions. A special version of this approach, the cluster‐continuum quasichemical model, has also been used for establishing a single‐ion solvation free energy scale in different solvents compatible with the tetraphenylarsonium tetraphenylborate assumption. The use of discrete‐continuum solvation methods can lead to meaningful improvement with respect to pure continuum solvation models for modeling diverse chemical process in solution. In the case of pKa calculations, there are cases where the root mean squared error is as large as 7 pKa units with pure continuum solvation model and becomes around 1 pKa unit with the hybrid approach. For complex reactions in solution, errors as large as 10 kcal/mol for activation free energies with the pure continuum approach can be substantially reduced with the inclusion of explicit solvent molecules. A discussion of the theory of hybrid discrete‐continuum methods is also presented and further development is expected in the coming years. This article is categorized under: Structure and Mechanism > Reaction Mechanisms and Catalysis Software > Quantum Chemistry Molecular and Statistical Mechanics > Free Energy Methods

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Section: Theorymentioning

confidence: 99%

Hybrid discrete‐continuum solvation methods

Pliego

Riveros

2019

WIREs Comput Mol Sci

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“…Some theoretical calculations have predicted that the NH 3 O isomer is sufficiently stable to be kinetically relevant and may play a key role in many reactions of HAN in aqueous solution [25][26][27][28]. Felnadez et al [26] calculated the value for the tautomeric equilibrium between NH 2 OH and…”

Section: The Neutral-neutral Reaction Of Nh 3 O and Hnomentioning

confidence: 99%

Decomposition Pathways for Aqueous Hydroxylammonium Nitrate Solutions: a DFT Study

Izato¹,

Koshi²,

Miyake³

2017

Cent. Eur. J. Energ. Mater.

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Hydroxylammmonium nitrate (hydroxylamine nitrate, HAN) is one of the most promising candidates as a replacement for commonly used liquid mono-propellants such as hydrazine. The reaction pathways involved in the initial and the catalytic decomposition of HAN in aqueous solution were determined using quantum chemistry calculations incorporating solvent effects. Optimized structures were obtained for the reactants, products and transition states at the ωB97XD/6-311++G(d,p)/SCRF = (solvent = water) level of theory and the total electron energies of these structures were calculated at the CBS-QB3 level of theory. In the initial decomposition, the ion-neutral NH3OH + -HNO3 reaction, the neutral-neutral NH3O-HNO3 reaction and the HNO3 self-decomposition pathways were all found to have reasonable energy barriers, with values of 91.7 kJ/mol, 88.7 kJ/mol and 89.8 kJ/mol, respectively. The overall reaction resulting from any of these pathways can be written as: HAN → HONO + HNO + H2O. The ionic reaction is dominant during the initial decomposition of HAN in aqueous solution because NH3OH+ and NO3 -are the major species in such solutions. We also developed six catalytic mechanisms and each of these schemes provided the same global reaction: NH2OH + HONO → N2O + 2H2O. The t-ONONO2 oxidizing scheme is the most plausible based on the energy barrier results.

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“…Two mechanisms were found for the nucleophilic attack of hydroxylamine on paraoxon, involving backside attack or frontside attack. In both cases, the first step was isomerization of neutral hydroxylamine to the zwitterion, a conversion that previous theoretical studies indicated to be favorable by 3.5 kcal mol −1 . A value of 6.6 kcal mol −1 was obtained using the M08‐HX method with SMD solvation (see Table ).…”

Section: Resultsmentioning

confidence: 99%

“…In relation to the choice of solvation method, it should be noted that the relative stabilities of neutral and zwitterion forms of hydroxylamine are difficult to describe, due to important solvent effects. A more reliable method, using an explicit solvent, was used to investigate this equilibrium, and it was found that a better description was obtained with the SM8 method, rather than the SMD method . Nevertheless, recent studies of anion‐molecule nucleophilic substitution reactions have indicated that SMD outperforms SM8 for reaction barriers in methanol solvent .…”

Section: Theoretical Calculationsmentioning

confidence: 99%

Cleaving paraoxon with hydroxylamine: Ammonium oxide isomer favors a Frontside attack mechanism

Lima

Cruz

Fernandes

et al. 2018

J of Physical Organic Chem

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A detailed molecular understanding of the mechanisms of the dephosphorylation of phosphate triesters due to nucleophilic attack can be very useful for the design of nucleophiles that are more efficient. In this work, we report a combined experimental and theoretical study of the reaction of hydroxylamine with paraoxon. The profile of the reaction rate according to pH was determined, and it was found that protonated hydroxylamine was unreactive, while the neutral form reacted via the zwitterion tautomer, with an overall free energy barrier of 23.0 kcal mol‐1. The anionic form was the most reactive, with a free energy barrier of 18.1 kcal mol‐1. Computational calculations revealed 2 mechanisms for the nucleophilic attack of the zwitterion form: the usual backside attack and a new frontside attack mechanism. The former proceeded according to a 2‐step associative mechanism, while the latter was a concerted single‐step mechanism involving attack of the hydroxylamine oxygen on the phosphorus center and interaction of the NH3+ group with the oxygen of the P═O group. The calculations indicated that the free energy barrier for the frontside attack was more favorable than the backside attack by 3 kcal mol‐1, supporting the notion that the observed reaction occurs by frontside attack. The reaction with the anionic hydroxylamine form occurred according to a single‐step concerted ANDN mechanism.

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Stability of hydroxylamine isomers in aqueous solution: Ab initio study using continuum, cluster-continuum and Shells Theory of Solvation

Cited by 16 publications

References 37 publications

Hybrid discrete‐continuum solvation methods

Hybrid discrete‐continuum solvation methods

Decomposition Pathways for Aqueous Hydroxylammonium Nitrate Solutions: a DFT Study

Cleaving paraoxon with hydroxylamine: Ammonium oxide isomer favors a Frontside attack mechanism

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