Nitrogen isotope exchange between nitric and nitrous acids

Akhtar, M. Humayoun; Axente, D.; Bonner, Francis T.

doi:10.1063/1.438813

Cited by 7 publications

(5 citation statements)

References 11 publications

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Section: Resultssupporting

confidence: 88%

“…This underscores the importance of accurately maintaining a constant temperature when studying this reaction. The activation energy of the reverse reaction was determined to be 76 ± 4 kJ mol −1 , in close agreement with the prior determination of 74 kJ mol −1 by Akhtar et al 29 A quantum chemistry study was undertaken to determine the origin of the high activation energy associated with K 4 2 k 5 . The gas-phase free energies and enthalpies of reactions 6−9 were established using the average results of the CBS-QB3 and G3B3 methods.…”

Section: ■ Experimental Sectionsupporting

confidence: 79%

“…In the presence of added nitrate or very high acid concentrations the reverse of reaction results in formation of NO 2 , reducing the net rate of nitrous acid decomposition. This reaction exhibits first-order dependencies on nitrous acid, hydrogen ion, and nitrate ion concentrations. , Analogous rate laws are observed for the nitrosation of a range of species by nitrous acid, suggesting that a similar mechanism operates for the reaction of nitrous acid and nitrate. The rate law for nitrous acid decomposition can be modified to incorporate the effect of this reaction by assuming that the rate of decomposition depends on the net rate of NO 2 hydrolysis, i.e., the net rate of reaction . 2 NO 2 + H 2 O ⇆ HNO 2 + NO 3 − + H + , k 5 , k − 5 normald [ H N O 2 ] normald t = − 3 K 4 2 k 5 false[ normalH normalN normalO 2 false] 4 false[ normalN normalO false] 2 + 3 k − 5 [ H N O 2 ] [ …”

Section: Resultsmentioning

confidence: 68%

“…This reaction exhibits first-order dependencies on nitrous acid, hydrogen ion, and nitrate ion concentrations. 28,29 Analogous rate laws are observed for the nitrosation of a range of species by nitrous acid, 4 suggesting that a similar mechanism operates for the reaction of nitrous acid and nitrate. The rate law for nitrous acid decomposition can be modified to incorporate the effect of this reaction by assuming that the rate of decomposition depends on the net rate of NO 2 hydrolysis, i.e., the net rate of reaction 5a.…”

Section: ■ Experimental Sectionmentioning

confidence: 86%

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Accurate Rate Constants for Decomposition of Aqueous Nitrous Acid

et al. 2012

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Decomposition of nitrous acid in aqueous solution has been studied by stopped flow spectrophotometry to resolve discrepancies in literature values for the rate constants of the decomposition reactions. Under the conditions employed, the rate-limiting reaction step comprises the hydrolysis of NO(2). A simplified rate law based on the known elementary reaction mechanism provides an excellent fit to the experimental data. The rate constant, 1.34 × 10(-6) M(-1) s(-1), is thought to be of higher accuracy than those in the literature as it does not depend on the rate of parallel reaction pathways or on the rate of interphase mass transfer of gaseous reaction products. The activation energy for the simplified rate law was established to be 107 kJ mol(-1). Quantum chemistry calculations indicate that the majority of the large activation energy results from the endothermic nature of the equilibrium 2HNO(2) ⇆ NO + NO(2) + H(2)O. The rate constant for the reaction between nitrate ions and nitrous acid, which inhibits HNO(2) decomposition, was also determined.

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Section: Resultssupporting

confidence: 88%

Section: ■ Experimental Sectionsupporting

confidence: 79%

Section: Resultsmentioning

confidence: 68%

Section: ■ Experimental Sectionmentioning

confidence: 86%

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Accurate Rate Constants for Decomposition of Aqueous Nitrous Acid

et al. 2012

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“…The atmospheric cycling of N r (reactive nitrogen) is a focus of both scientific and policy concern, because of the importance of N r in controlling the formation of tropospheric ozone. Atmospheric N r also plays a role in the formation of particulate matter and its long-range transport modifies the global carbon cycle by providing nitrogen fertilization to remote ecosystems. , Measurements of stable nitrogen isotope ratios offer a means of discriminating sources of nitrogen and reactions involved in N r cycling via their specific isotopic signatures. − The potential of using the stable nitrogen isotopic signatures of airborne particles to deepen our understanding of the sources, reactivity, transport, and removal of atmospheric nitrogen species has been recognized for a long time . Its application to real world samples, however, has suffered due to multiple analytical challenges.…”

mentioning

confidence: 99%

Speciation of Nitrogen-Bearing Species Using Negative and Positive Secondary Ion Spectra with Nano Secondary Ion Mass Spectrometry

Sinha

Hoppe

2016

Anal. Chem.

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In this study, we demonstrate that Nano Secondary Ion Mass Spectrometry (NanoSIMS) can be used to differentiate different nitrogen-containing species commonly observed in atmospheric aerosol particles with micrometer or submicrometer spatial resolution, on the basis of the relative intensity of secondary ion signals, both in negative and positive secondary ion mode, without the need to chemically or physically separate the samples. Compounds tested include nitrate, nitrite, ammonium salts, urea, amino acids, sugars, organic acids, amides, triazine, imidazole, protein, and biological tissue. We show that NO2(-) secondary ions are unique to the decomposition of nitrate and nitrite salts, whereas NH4(+) secondary ions are unique to samples containing ammonium ions, with low signal intensities observed from amino groups but none from biological tissue. CN(-) signals are obtained from all nitrogen-bearing compounds, but relative signal intensities are the highest for organic nitrogen-containing compounds. We demonstrate that quantitative determination of the elemental fractions of carbon, oxygen, and nitrate in nanometer-sized aerosol samples using normalized secondary ion intensities is possible. We further demonstrate that stable isotope ratios measured on in-house standards of unknown isotopic composition using the (12)C(15)N(-)/(12)C(14)N(-) ratio (all nitrogen-containing species), the (15)N(16)O2(-)/(14)N(16)O2(-) ratio (nitrate and nitrite species), and the (15)NH4(+)/(14)NH4(+) ratio (ammonium salts, amino acids, and urea) are stable and sufficiently precise for nitrogen isotope analysis.

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