Dimerization Of Nitrogen Dioxide Research Articles

Metal-free catalysis for the reaction of nitrogen dioxide dimer with phenol: An unexpected favorable source of nitrate and aerosol precursors in vehicle exhaust

Atmospheric reaction mechanism and dynamics of phenol with nitrogen dioxide dimer were explored by the density functional theory and high-level quantum chemistry combined with statistical kinetic calculations within 220–800 K. The nitric acid and phenyl nitrite, the typical aerosol precursors, are the preponderant products because of the low formation free energy barrier (∼8.7 kcal/mol) and fast rate constants (∼10−15 cm3 molecule−1 s−1 at 298 K). Phenyl nitrate is the minor product and it would be also formed from the transformation of phenyl nitrite in NO2-rich environment. More importantly, kinetic effects and catalytic mechanism of a series of metal-free catalysts (H2O, NH3, CH3NH2, CH3NHCH3, HCOOH, and CH3COOH) on the title reaction were investigated at the same level. The results indicate that CH3NH2 and CH3NHCH3 can not only catalyze the title reaction by lowering the free energy barrier (about 1.4–6.5 kcal/mol) but also facilitate the production of organic ammonium nitrate via acting as a donor-acceptor of hydrogen. Conversely, the other species are non-catalytic upon the title reaction. The stabilization energies and donor-acceptor interactions in alkali-catalyzed product complexes were explored, which can provide new insights to the properties of aerosol precursors. Moreover, the lifetime of phenol determined by nitrogen dioxide dimer in the presence of dimethylamine may compete with that of determined by OH radicals, indicating that nitrogen dioxide dimer is responsible for the elimination of phenol in the polluted atmosphere. This work could help us thoroughly understand the removal of nitrogen oxides and phenol as well as new aerosol precursor aggregation in vehicle exhaust.

The gas-phase structure of the asymmetric, trans-dinitrogen tetroxide (N2O4), formed by dimerization of nitrogen dioxide (NO2), from rotational spectroscopy and ab initio quantum chemistry.

We report the first experimental gas-phase observation of an asymmetric, trans-N2O4 formed by the dimerization of NO2. In additional to the dominant 14N216O4 species, rotational transitions have been observed for all species with single 15N and 18O substitutions as well as several multiply substituted isotopologues. These transitions were used to determine a complete substitution structure as well as an r0 structure from the fitted zero-point averaged rotational constants. The determined structure is found to be that of an ON-O-NO2 linkage with the shared oxygen atom closer to the NO2 than the NO (1.42 vs 1.61 Å). The structure is found to be nearly planar with a trans O-N-O-N linkage. From the spectra of the 14N15NO4 species, we were able to determine the nuclear quadrupole coupling constants for each specific nitrogen atom. The equilibrium structure determined by ab initio quantum chemistry calculations is in excellent agreement with the experimentally determined structure. No spectral evidence of the predicted asymmetric, cis-N2O4 was found in the spectra.

Fourier transform and multiplexed intrapulse quantum cascade laser spectrometer measurements of NO2 and its dimer N2O4

A quantitative comparison has been made between the spectra recorded using an infrared Fourier transform (FT) spectrometer, and those based upon the use of chirped pulse quantum cascade (QC) lasers. The system chosen for this comparison is the chemical equilibrium between NO2 and its dimer N2O4. It is studied by making spectroscopic measurements of the dimerization of nitrogen dioxide (NO2). The intrapulse QC laser spectrometer used long duration pulses of wavelengths near 7.84, 7.46, and 6.14 μm, and a path length of 62 m, and the Université libre de Bruxelles (Brussels, Belgium) FTspectrometer used a path length of 21.1 cm. In the direct comparison of pairs of spectral regions allowed by the dual pulse system, it was possible to compare the 7.84 μm region, where both the spectra of the monomer and dimer are observed, with the 7.46 and 6.14 μm regions in which only monomer lines are detected. In the 7.84 μm region the NO2 absorption lines could be detected only when the dimer N2O4 is formed in the monomer NO2 in the QC laser spectra.

Ion-Radical Conversions in Main or Side Chains of Nitrogen-Containing Polymers in Nitrogen Dioxide Atmosphere

Mechanism of nitrogen dioxide interaction with polymers containing amide and imide groups in the main or side chains of macromolecules (polycaproamide, polyvinylpyrrolidone, poly-m-phenylene isophthalamide and polypyromellitimide) is considered. The initiators of conversions of polymers of the given classes are not monoradicals of nitrogen dioxide rather than its equilibrium dimers in the form of nitrosyl nitrate. In primary oxidizing reaction of an electron transfer from donor groups of macromolecules to nitrosyl nitrate, radical cations, nitric oxide and nitrate anion are formed, which in the subsequent reactions give products of nitration and nitrosation. These products are precursors of stable acylalkylaminoxyl, acylarylaminoxyl, iminoxyl macroradicals. The specific interactions of nitrogen dioxide dimers with functional groups of macromolecules determine features of the mechanism of ion-radical conversions of the polymers and the composition of radical and molecular products. The direct detection of radical cations has been realized by ESR method for confirmation of the ion-radical initiation concept using model reaction of nitrogen dioxide with triphenylamine.

Understanding Chemical Equilibrium Using Entropy Analysis: The Relationship Between ΔStot(syso) and the Equilibrium Constant

Entropy analyses as a function of the extent of reaction are presented for a number of physicochemical processes, including vaporization of a liquid, dimerization of nitrogen dioxide, and the autoionization of water. Graphs of the total entropy change versus the extent of reaction give a visual representation of chemical equilibrium and the second law of thermodynamics. The mathematical relationship between the total entropy change for the system under standard-state conditions and the equilibrium constant is derived exclusively from entropy analysis.

Oxidative radical generation via nitrogen dioxide dimer conversions induced by amide groups of macromolecules

The features of initiation of free radical reactions in polymers by dimers of nitrogen dioxide are considered. The conversion of planar dimers into nitrosyl nitrate in the presence of amide groups of macromolecules has been revealed. Nitrosyl nitrate initiates radical reactions in oxidative primary process of electron transfer with formation of intermediate radical cations and nitric oxide. As a result of subsequent reactions, nitrogen-containing radicals are produced. The dimer conversion has been exhibited by estimation of the oxyaminoxyl radical yield in characteristic reaction of p-benzoquinone with nitrogen dioxide on addition of aromatic polyamide and polyvinylpyrrolidone to reacting system. The isomerization of planar dimers is efficient in their complexes with amide groups, as confirmed by ab initio calculations. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Ion-radical mechanism of polymer-nitrogen dioxide interaction

By the example of poly(2-vinylpyridine), the ion-radical mechanism is established for the generation of stable nitrogen-containing radicals in polymers under the effect of nitrogen dioxide. The mechanism includes the reactions of nitrogen dioxide dimers occurring in the form of nitrosonium-nitrate ion pairs. The ion-radical process is induced by electron transfer from donor groups of macromolecules to nitrosonium cations that results in the formation of cation-macroradicals and nitrogen oxide. Stable radicals are generated in the course of subsequent reactions of these particles and lead to the formation of macromolecular nitroso compounds, which are efficient spin traps.

3.508μ-HeXe-laser line absorption by formaldehyde monomer and dimer and by nitrogen dioxide monomer and dimer without and in the presence of argon

Transmission of a single-mode HeXe-laser line at ω L = 2850.633 cm −1 through formaldehyde at room-temperature reveals off-center single-line absorption in the 5 1,5( ν 5 = 0) → 6 0,6( ν 5 = 1) transition by formaldehyde monomer (Fm) and line-center absorption by a formaldehyde dimer (Fd) which is Lorentzian for formaldehyde partial pressures of p ≳ 0.1 atm. Coefficients for self- and foreign-broadening of the monomer by dimer, argon, nitrogen dioxide monomer, and nitrogen dioxide dimer were determined by taking into account the laser-absorption by formaldehyde dimer and, where applicable, by nitrogen dioxide monomer (1) and dimer (2). The results at T 0 = 300°K are b Fm 0 ≡ b Fm Fm 0 (⋍b Fm Fd 0) = 6.13 × 10 −1 cm −1- atm −1 (±3.0%) , b Fm Ar 0 = 3.92 × 10 −2 cm −1-atm −1 (±5.5%), b Fm 2 0 ⪡ b Fm 1 0 = 3.22 × 10 −1 cm −1-atm −1 (±8.8%) based upon a dimer absorption governed by SK/ b Ed 0 = 36.7 cm −1-atm −2 (±0.7%) with the equilibrium constant K Ed 0 = ( p Fd/ p Fm 2) eq at 300°K and a previously established 9 high-precision value for the monomer line-strength of S Fm 0 = 6.81 × 10 −1 cm −2-atm −1 (±0.5%). Best data correlations were obtained with b Fd 0 ≡ b Fd Fm 0 ⋍ b Fd Fd 0 ⋍ b Fd Ar 0 ⋍ b Fd 1 0 ⋍ b Fd 2 0 for (H 2CO) x Ar and (H 2CO) x Ar mixtures. A high-precision value of ω Fm − ω L = 5.80 × 10 −3 cm −1 (±0.55%) was obtained by low-pressure ( p ≲ 1.6 × 10 −3 atm) pure formaldehyde laser-absorption with the above values for b Fm 0 and S Fm 0. Room-temperature results of HeXe-laser absorption at 3.508μ by NO 2 monomer (1) and dimer (2) at total pressures p ≳ 0.13 atm could best be interpreted by far-wing line-absorption for NO 2 and Lorentzian line-center absorption for N 2O 4. The corresponding absorption coefficients at T 0 = 300°K are Sb/ Δω 2 π) 1 0 p = 4.90 × 10 −2/( p/atm) cm −1-atm −1 (±5.2%) and S/ bπ) 2 0/ p = 8.44 × 10 −3/( p/atm) cm −1-atm −1 (±4.6%) with b 1 0 ≡ b 11 0 ⋍ b 12 0 and b 12 0 ≡ b 22 0 ⋍ b 21 0 . The present low-temperature results and previous high-temperature shock-tube laser-absorption data for formaldehyde-argon mixtures were combined and interpreted in terms of formaldehyde monomer and dimer absorption. The resulting temperature dependences for the line-strengths are S Fm( T) = S Fm 0( T 0/ T) m with m = 1.79 (±7.3%) for the monomer and (SK/b) Fd (T) = (SK/b) Fd 0(T/T 0) n + 1 2 exp[+( ΔH 0/ RT 0) × ( T 0/ T − 1)] with n = 1.36 (±20%) and ΔH 0 = 940 cal/mole 12 for the dimer for T ⪅ 1600°K.

Dimerization of nitrogen dioxide in solution: a comparison of solution thermodynamics with the gas phase

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDimerization of nitrogen dioxide in solution: a comparison of solution thermodynamics with the gas phaseThomas F. Redmond and Bradford B. WaylandCite this: J. Phys. Chem. 1968, 72, 5, 1626–1629Publication Date (Print):May 1, 1968Publication History Published online1 May 2002Published inissue 1 May 1968https://doi.org/10.1021/j100851a040RIGHTS & PERMISSIONSArticle Views450Altmetric-Citations45LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (432 KB) Get e-Alerts