Dataset Information

Atmospheric Chemistry of 2-Amino-2-methyl-1-propanol: A Theoretical and Experimental Study of the OH-Initiated Degradation under Simulated Atmospheric Conditions.

ABSTRACT: The OH-initiated degradation of 2-amino-2-methyl-1-propanol [CH₃C(NH₂)(CH₃)CH₂OH, AMP] was investigated in a large atmospheric simulation chamber, employing time-resolved online high-resolution proton-transfer reaction-time-of-flight mass spectrometry (PTR-ToF-MS) and chemical analysis of aerosol online PTR-ToF-MS (CHARON-PTR-ToF-MS) instrumentation, and by theoretical calculations based on M06-2X/aug-cc-pVTZ quantum chemistry results and master equation modeling of the pivotal reaction steps. The quantum chemistry calculations reproduce the experimental rate coefficient of the AMP + OH reaction, aligning k(T) = 5.2 × 10^-12 × exp (505/T) cm³ molecule^-1 s^-1 to the experimental value k_exp,300K = 2.8 × 10^-11 cm³ molecule^-1 s^-1. The theoretical calculations predict that the AMP + OH reaction proceeds via hydrogen abstraction from the -CH₃ groups (5-10%), -CH₂- group, (>70%) and -NH₂ group (5-20%), whereas hydrogen abstraction from the -OH group can be disregarded under atmospheric conditions. A detailed mechanism for atmospheric AMP degradation was obtained as part of the theoretical study. The photo-oxidation experiments show 2-amino-2-methylpropanal [CH₃C(NH₂)(CH₃)CHO] as the major gas-phase product and propan-2-imine [(CH₃)₂C═NH], 2-iminopropanol [(CH₃)(CH₂OH)C═NH], acetamide [CH₃C(O)NH₂], formaldehyde (CH₂O), and nitramine 2-methyl-2-(nitroamino)-1-propanol [AMPNO₂, CH₃C(CH₃)(NHNO₂)CH₂OH] as minor primary products; there is no experimental evidence of nitrosamine formation. The branching in the initial H abstraction by OH radicals was derived in analyses of the temporal gas-phase product profiles to be B_CH₃/B_CH₂/B_NH₂ = 6:70:24. Secondary photo-oxidation products and products resulting from particle and surface processing of the primary gas-phase products were also observed and quantified. All the photo-oxidation experiments were accompanied by extensive particle formation that was initiated by the reaction of AMP with nitric acid and that mainly consisted of this salt. Minor amounts of the gas-phase photo-oxidation products, including AMPNO₂, were detected in the particles by CHARON-PTR-ToF-MS and GC×GC-NCD. Volatility measurements of laboratory-generated AMP nitrate nanoparticles gave Δ_vapH = 80 ± 16 kJ mol^-1 and an estimated vapor pressure of (1.3 ± 0.3) × 10^-5 Pa at 298 K. The atmospheric chemistry of AMP is evaluated and a validated chemistry model for implementation in dispersion models is presented.

SUBMITTER: Tan W

PROVIDER: S-EPMC8419843 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Similar Datasets

Project description:The OH-initiated photo-oxidation of piperidine and the photolysis of 1-nitrosopiperidine were investigated in a large atmospheric simulation chamber and in theoretical calculations based on CCSD(T*)-F12a/aug-cc-pVTZ//M062X/aug-cc-pVTZ quantum chemistry results and master equation modeling of the pivotal reaction steps. The rate coefficient for the reaction of piperidine with OH radicals was determined by the relative rate method to be kOH-piperidine = (1.19 ± 0.27) × 10-10 cm3 molecule-1 s-1 at 304 ± 2 K and 1014 ± 2 hPa. Product studies show the piperidine + OH reaction to proceed via H-abstraction from both CH2 and NH groups, resulting in the formation of the corresponding imine (2,3,4,5-tetrahydropyridine) as the major product and in the nitramine (1-nitropiperidine) and nitrosamine (1-nitrosopiperidine) as minor products. Analysis of 1-nitrosopiperidine photolysis experiments under natural sunlight conditions gave the relative rates jrel = j1-nitrosoperidine/jNO2 = 0.342 ± 0.007, k3/k4a = 0.53 ± 0.05 and k2/k4a = (7.66 ± 0.18) × 10-8 that were subsequently employed in modeling the piperidine photo-oxidation experiments, from which the initial branchings between H-abstraction from the NH and CH2 groups, kN-H/ktot = 0.38 ± 0.08 and kC2-H/ktot = 0.49 ± 0.19, were derived. All photo-oxidation experiments were accompanied by particle formation that was initiated by the acid-base reaction of piperidine with nitric acid. Primary photo-oxidation products including both 1-nitrosopiperidine and 1-nitropiperidine were detected in the particles formed. Quantum chemistry calculations on the OH initiated atmospheric photo-oxidation of piperidine suggest the branching in the initial H-abstraction routes to be ∼35% N1, ∼50% C2, ∼13% C3, and ∼2% C4. The theoretical study produced an atmospheric photo-oxidation mechanism, according to which H-abstraction from the C2 position predominantly leads to 2,3,4,5-tetrahydropyridine and H-abstraction from the C3 position results in ring opening followed by a complex autoxidation, of which the first few steps are mapped in detail. H-abstraction from the C4 position is shown to result mainly in the formation of piperidin-4-one and 2,3,4,5-tetrahydropyridin-4-ol, whereas H-abstraction from N1 under atmospheric conditions primarily leads to 2,3,4,5-tetrahydropyridine and in minor amounts of 1-nitrosopiperidine and 1-nitropiperidine. The calculated rate coefficient for the piperidine + OH reaction agrees with the experimental value within 35%, and aligning the theoretical numbers to the experimental value results in k(T) = 2.46 × 10-12 × exp(486 K/T) cm3 molecule-1 s-1 (200-400 K).

Project description:The present relative kinetic study reports on the experimentally determined gas-phase reaction rate coefficients of OH radicals with a series of seven cis-3-hexenyl esters. The experiments were carried out in the environmental simulation chamber made of quartz from the "Alexandru Ioan Cuza" University of Iasi (ESC-Q-UAIC), Romania, at a temperature of (298 ± 2) K and a total air pressure of (1000 ± 10) mbar. In situ long-path Fourier transform infrared (FTIR) spectroscopy was used to monitor cis-3-hexenyl formate (Z3HF, (Z)-CH3CH2CH═CH(CH2)2OC(O)H), cis-3-hexenyl acetate (Z3HAc, (Z)-CH3CH2CH═CH(CH2)2OC(O)CH3), cis-3-hexenyl isobutyrate (Z3HiB, (Z)-CH3CH2CH═CH(CH2)2OC(O)CH(CH3)2), cis-3-hexenyl 3-methylbutanoate (Z3H3MeB, (Z)-CH3CH2CH═CH(CH2)2OC(O)CH2CH(CH3)2), cis-3-hexenyl hexanoate (Z3HH, (Z)-CH3CH2CH═CH(CH2)2OC(O)(CH2)4CH3), cis-3-hexenyl cis-3-hexenoate (Z3HZ3H, (Z,Z)-CH3CH2CH═CH(CH2)2OC(O)CH2CH═CHCH2CH3), cis-3-hexenyl benzoate (Z3HBz, (Z)-CH3CH2CH═CH(CH2)2OC(O)C6H5), and the reference compounds. The following reaction rate coefficients (in 10-11 cm3 molecule-1 s-1) were obtained for the OH radical-initiated gas-phase oxidation of cis-3-hexenyl esters: (4.13 ± 0.45) for Z3HF, (4.19 ± 0.38) for Z3HAc, (4.84 ± 0.39) for Z3HiB, (5.39 ± 0.61) for Z3H3MeB, (7.00 ± 0.56) for Z3HH, (10.58 ± 1.40) for Z3HZ3H, and (3.41 ± 0.28) for Z3HBz. The results are discussed in terms of hexenyl ester reactivity and compared with the available literature data and structure-activity relationship (SAR) estimates. The atmospheric implications based on the average lifetimes of the investigated cis-3-hexenyl esters are discussed in the present study. The gas-phase rate coefficients for OH radical reactions are given herein for the first time for cis-3-hexenyl isobutyrate, cis-3-hexenyl 3-methylbutanoate, cis-3-hexenyl hexanoate cis-3-hexenyl cis-3-hexenoate, and cis-3-hexenyl benzoate. The newly determined gas-phase reaction rate coefficients provide new information for existing kinetic databases and contribute to the further development of SAR methodologies useful for predicting the reactivity of oxygenated volatile organic compounds.

Dataset Information

Atmospheric Chemistry of 2-Amino-2-methyl-1-propanol: A Theoretical and Experimental Study of the OH-Initiated Degradation under Simulated Atmospheric Conditions.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets