Recombination of 1,1-dimethylpropyl peroxy radicals in polar solvents

Denisova, T. G.; Shuvalov, V. F.

doi:10.1134/s0023158416010031

Cited by 4 publications

(4 citation statements)

References 2 publications

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“…The rate coefficient for hydroxymethyl radical recombination with O 2 forming methanol hydroperoxyl, • CH 2 OH + O 2 ⇌ HO-CH 2 OO • , was taken from a literature CBS-QB3 level of theory calculation, 35 and the rate coefficient of formaldehyde condensation with water, CH 2 O + H 2 O ⇌ HOCH 2 OH, was taken from an experimental measurement at 20−50 °C and a pH range of 5−7. 36 38 and an average of recommended rates for a similar tert-alkyl system, 39 respectively. Additional liquid phase rate coefficients for radical recombination with molecular oxygen were taken from literature 40 and added as training reactions into RMG's database.…”

Section: Methodsmentioning

confidence: 99%

“…An experimental rate coefficient was used for hydroxymethyl hydroperoxide decomposition into formaldehyde and hydrogen peroxide, HOCH 2 OOH ⇌ CH 2 O + H 2 O 2 . Rate coefficients of cyanoisopropyl peroxyl radical recombination into a tetroxide and its subsequent homolysis into two cyanoisopropyl alkoxyl radicals and O 2 were taken from a 298 K experimental study and an average of recommended rates for a similar tert -alkyl system, respectively. Additional liquid phase rate coefficients for radical recombination with molecular oxygen were taken from literature and added as training reactions into RMG’s database.…”

Section: Methodsmentioning

confidence: 99%

“…The AIBN homolysis rate coefficient was obtained from a literature measurement of the evolved nitrogen gas at constant pressure at 90-107°C, [7] and extrapolated to the relevant system temperature. [37] and an average of recommended rates for a similar tert-alkyl system, [38] respectively. Additional liquid phase rate coefficients for radical recombination with molecular oxygen were taken from literature [39] and added as training reactions into RMG's database.…”

Section: Model Generationmentioning

confidence: 99%

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Kinetic Modeling of API Oxidation: (1) The AIBN/H₂O/CH₃OH Radical “Soup”

Dana

Ranasinghe

et al. 2021

Mol. Pharmaceutics

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While different flavors of API stress testing systems have been used in experimental investigations for decades, the detailed kinetics of such systems as well as the chemical composition of prominent reactive species, specifically reactive oxygen species, are unknown.As a first step toward understanding and modeling API oxidation in stress testing, we investigated a typical radical "soup" solution an API is subject to during stress testing.Here we applied ab-initio electronic structure calculations to automatically generate and refine a detailed chemical kinetics model, taking a fresh look at API oxidation.We generated a detailed kinetic model for a representative azobisisobutyronitrile (AIBN)/H 2 O/CH 3 OH stress-testing system with varied co-solvent ratio (50%/50% --99.5%/0.5% vol. water/methanol) and for representative pH values (4--10) at 40oC stirred and open to the atmosphere.At acidic conditions hydroxymethyl alkoxyl is the dominant alkoxyl radical, and at basic conditions, for most studied initial methanol concentrations, cyanoisopropyl alkoxyl becomes the dominant alkoxyl radical, albeit at an overall lower concentration.At acidic conditions the levels of cyanoisopropyl peroxyl, hydroxymethyl peroxyl, and hydroperoxyl radicals are relatively high and comparable, while at both neutral and basic pH conditions, superoxide becomes the prominent radical in the system.The present work reveals the prominent species in a common model API stress testing system at various co-solvent and pH conditions, sets the stage for an in-depth quantitative API kinetic study, and demonstrates usage of novel software tools for automated chemical kinetic model generation and ab-initio refinement. File list (2) download file view on ChemRxiv 2021.04.01 a The Soup.pdf (5.01 MiB) download file view on ChemRxiv 2021.01.29 a Soup SI.pdf (1.02 MiB)

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Model Generationmentioning

confidence: 99%

See 1 more Smart Citation

Kinetic Modeling of API Oxidation: (1) The AIBN/H₂O/CH₃OH Radical “Soup”

Dana

Ranasinghe

et al. 2021

Mol. Pharmaceutics

View full text Add to dashboard Cite

show abstract

“…The AIBN homolysis rate coefficient was obtained from a literature measurement of the evolved nitrogen gas at constant pressure at 90-107 °C, [7] and extrapolated to the relevant system temperature. [37] and an average of recommended rates for a similar tert-alkyl system, [38] respectively. Additional liquid phase rate coefficients for radical recombination with molecular oxygen were taken from literature [39] and added as training reactions into RMG's database.…”

Section: Model Generationmentioning

confidence: 99%

Kinetic Modeling of API Oxidation: 1. The AIBN/H2O/CH3OH Radical "Soup"

Dana

Wu²,

Ranasinghe³

et al. 2021

Preprint

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While different flavors of API stress testing systems have been used in experimental investigations for decades, the detailed kinetics of such systems as well as the chemical composition of prominent reactive species, specifically reactive oxygen species, are unknown. As a first step toward understanding and modeling API oxidation in stress testing, we investigated a typical radical "soup" solution an API is subject to during stress testing. Here we applied ab-initio electronic structure calculations to automatically generate and refine a detailed chemical kinetics model, taking a fresh look at API oxidation. We generated a detailed kinetic model for a representative azobisisobutyronitrile (AIBN)/H2O/CH3OH stress-testing system with varied co-solvent ratio (50%/50% -- 99.5%/0.5% vol. water/methanol) and for representative pH values (4--10) at 40oC stirred and open to the atmosphere. At acidic conditions hydroxymethyl alkoxyl is the dominant alkoxyl radical, and at basic conditions, for most studied initial methanol concentrations, cyanoisopropyl alkoxyl becomes the dominant alkoxyl radical, albeit at an overall lower concentration. At acidic conditions the levels of cyanoisopropyl peroxyl, hydroxymethyl peroxyl, and hydroperoxyl radicals are relatively high and comparable, while at both neutral and basic pH conditions, superoxide becomes the prominent radical in the system. The present work reveals the prominent species in a common model API stress testing system at various co-solvent and pH conditions, sets the stage for an in-depth quantitative API kinetic study, and demonstrates usage of novel software tools for automated chemical kinetic model generation and ab-initio refinement.

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