Equilibrium structure and energetics of CHNO isomers: Steps towards ab initio rovibrational spectra of quasi-linear molecules

Mladenović, Mirjana; Lewerenz, Marius

doi:10.1016/j.chemphys.2007.06.033

Cited by 37 publications

(52 citation statements)

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“…The NCO − ion could arise either from HOCN, cyanic acid, or HNCO, (isocyanic acid). While cyanate salts, such as sodium cyanate (NaOCN), are known to be stable, they evolve HNCO vapor upon acidification (Fischer et al, 2002), and HNCO has been shown to be the most thermodynamically stable of the possible CHNO isomers (Mladenovic and Lewerenz, 2008). There are several studies of the pyrolysis of biomass, coal, and polyamides, that have unambiguously identified HNCO as a major product by infrared spectroscopy (Hansson et al, 2004;Nelson et al, 1996).…”

Section: Isocyanic Acid (Hnco)mentioning

confidence: 99%

Measurement of HONO, HNCO, and other inorganic acids by negative-ion proton-transfer chemical-ionization mass spectrometry (NI-PT-CIMS): application to biomass burning emissions

et al. 2010

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Abstract. A negative-ion proton-transfer chemical ionization mass spectrometric technique (NI-PT-CIMS), using acetate as the reagent ion, was applied to the measurement of volatile inorganic acids of atmospheric interest: hydrochloric (HCl), nitrous (HONO), nitric (HNO 3 ), and isocyanic (HNCO) acids. Gas phase calibrations through the sampling inlet showed the method to be intrinsically sensitive (6-16 cts/pptv), but prone to inlet effects for HNO 3 and HCl. The ion chemistry was found to be insensitive to water vapor concentrations, in agreement with previous studies of carboxylic acids. The inlet equilibration times for HNCO and HONO were 2 to 4 s, allowing for measurement in biomass burning studies. Several potential interferences in HONO measurements were examined: decomposition of HNO 3 ·NO − 3 clusters within the CIMS, and NO 2 -water production on inlet surfaces, and were quite minor (≤1%, 3.3%, respectively). The detection limits of the method were limited by the instrument backgrounds in the ion source and flow tube, and were estimated to range between 16 and 50 pptv (parts per trillion by volume) for a 1 min average. The comparison of HONO measured by CIMS and by in situ FTIR showed good correlation and agreement to within 17%. The method provided rapid and accurate measurements of HNCO and HONO in controlled biomass burning studies, in which both acids were seen to be important products.

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Section: Isocyanic Acid (Hnco)mentioning

confidence: 99%

Measurement of HONO, HNCO, and other inorganic acids by negative-ion proton-transfer chemical-ionization mass spectrometry (NI-PT-CIMS): application to biomass burning emissions

et al. 2010

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“…HNCO is also the simplest species containing all four most abundant elements, H, N, C and O, and four isomers have this elemental composition: isocyanic acid HNCO, cyanic acid HOCN, fulminic acid HCNO and isofulminic acid HONC. HNCO is the most stable isomer, and ab initio calculations give the energies of their ground electronic singlet states relative to HNCO to be 24.7, 70.7 and 84.1 kcal mol −1 , respectively (Mladenović & Lewerenz 2008). However, it is only recently that fulminic acid HCNO has been detected and the HNCO/HCNO abundance ratio is observed to change by one order of magnitude depending on the object (Marcelino et al 2009).…”

Section: Introductionmentioning

confidence: 99%

Kinetics of the OCN⁻and HOCN formation from the HNCO + H₂O thermal reaction in interstellar ice analogs

Theulé

Duvernay

Ilmane

et al. 2011

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Aims. We study in the laboratory the kinetics of the low-temperature OCN − and HOCN formation from the purely thermal reaction of solid HNCO and H 2 O. The cyanate ion OCN − is an intermediate in the isomerization process of isocyanic acid HNCO into cyanic acid HOCN in water ice. Methods. We study the reaction, isomerization and desorption kinetics of the HNCO/OCN − /HOCN system using Fourier transform infrared spectroscopy. Results. Activation energies of 26 ± 2 kJ mol −1 (3127 K) and 36 ± 1 kJ mol −1 (4330 K) are found for the HNCO + H 2 O → OCN − + H 3 O + and OCN − + H 3 O + → HOCN + H 2 O reactions respectively. Desorption energies of 37 ± 3 kJ mol −1 (4450 K) and 40 ± 3 kJ mol −1 (4811 K) are measured for HNCO and OCN − , respectively. Conclusions. The present experiment has the important implication that the H 2 O + HNCO reaction alone cannot account for the observed abundances of solid OCN − in astronomical IR sources.

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“…Until recently, the interest in studying HNCO was from a fundamental science perspective with research conducted on its structure, preparation and physical properties (Belson and Strachan, 1982) and on its theoretical rovibrational spectra (Mladenović and Lewerenz, 2008). Both theoretical and experimental data indicate that HNCO is the most stable CHNO isomer with a near-linear π -bond system (Hocking et al, 1975;Jones et al, 1950;Poppinger et al, 1977).…”

Section: Introductionmentioning

confidence: 99%

Solubility and reactivity of HNCO in water: insights into HNCO's fate in the atmosphere

et al. 2016

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Abstract.A growing number of ambient measurements of isocyanic acid (HNCO) are being made, yet little is known about its fate in the atmosphere. To better understand HNCO's loss processes and particularly its atmospheric partitioning behaviour, we measure its effective Henry's Law coefficient K eff H with a bubbler experiment using chemical ionization mass spectrometry as the gas phase analytical technique. By conducting experiments at different pH values and temperature, a Henry's Law coefficient K H of 26 ± 2 M atm −1 is obtained, with an enthalpy of dissolution of −34 ± 2 kJ mol −1 , which translates to a K eff H of 31 M atm −1 at 298 K and at pH 3. Our approach also allows for the determination of HNCO's acid dissociation constant, which we determine to be K a = 2.1 ± 0.2 × 10 −4 M at 298 K. Furthermore, by using ion chromatography to analyze aqueous solution composition, we revisit the hydrolysis kinetics of HNCO at different pH and temperature conditions. Three pH-dependent hydrolysis mechanisms are in play and we determine the Arrhenius expressions for each rate to be k 1 = (4.4 ± 0.2) × 10 7 exp(−6000 ± 240/T ) M s −1 , k 2 = (8.9 ± 0.9) × 10 6 exp(−6770 ± 450/T ) s −1 and k 3 = (7.2 ± 1.5) × 10 8 exp(−10 900 ± 1400/T ) s −1 , where k 1 is for HNCO + H + + H 2 O → NH + 4 + CO 2 , k 2 is for HNCO + H 2 O → NH 3 + CO 2 and k 3 is for NCO − + 2 H 2 O → NH 3 + HCO − 3 . HNCO's lifetime against hydrolysis is therefore estimated to be 10 days to 28 years at pH values, liquid water contents, and temperatures relevant to tropospheric clouds, years in oceans and months in human blood. In all, a better parameterized Henry's Law coefficient and hydrolysis rates of HNCO allow for more accurate predictions of its concentration in the atmosphere and consequently help define exposure of this toxic molecule.

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Equilibrium structure and energetics of CHNO isomers: Steps towards ab initio rovibrational spectra of quasi-linear molecules

Cited by 37 publications

References 44 publications

Measurement of HONO, HNCO, and other inorganic acids by negative-ion proton-transfer chemical-ionization mass spectrometry (NI-PT-CIMS): application to biomass burning emissions

Measurement of HONO, HNCO, and other inorganic acids by negative-ion proton-transfer chemical-ionization mass spectrometry (NI-PT-CIMS): application to biomass burning emissions

Kinetics of the OCN⁻and HOCN formation from the HNCO + H₂O thermal reaction in interstellar ice analogs

Solubility and reactivity of HNCO in water: insights into HNCO's fate in the atmosphere

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Equilibrium structure and energetics of CHNO isomers: Steps towards ab initio rovibrational spectra of quasi-linear molecules

Cited by 37 publications

References 44 publications

Measurement of HONO, HNCO, and other inorganic acids by negative-ion proton-transfer chemical-ionization mass spectrometry (NI-PT-CIMS): application to biomass burning emissions

Measurement of HONO, HNCO, and other inorganic acids by negative-ion proton-transfer chemical-ionization mass spectrometry (NI-PT-CIMS): application to biomass burning emissions

Kinetics of the OCN−and HOCN formation from the HNCO + H2O thermal reaction in interstellar ice analogs

Solubility and reactivity of HNCO in water: insights into HNCO's fate in the atmosphere

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Kinetics of the OCN⁻and HOCN formation from the HNCO + H₂O thermal reaction in interstellar ice analogs