Comment on "Theoretical study of the NO3 radical reaction with CH2ClBr, CH2ICl, CH2BrI, CHCl2Br, and CHClBr2" by I. Alkorta, J. M. C. Plane, J. Elguero, J. Z. Dávalos, A. U. Acuña and A. Saiz-Lopez, Phys. Chem. Chem. Phys. 2022, 24, 14365.

This comment addresses a systematic error in the potential energy surfaces of the title reactions presented in the original article by Alkorta et al. The NO3 radical has D3h symmetry in the electronic ground state while the M08HX functional employed in the original article predicts an incorrect C2v geometry and energy. By combining thermodynamic data for the OH + HNO3 → H2O + NO3 reaction with spectroscopic data and results from M08HX calculations on HNO3, H2O and the OH radical, the ground state NO3 radical energy is estimated to be 37 kJ mol-1 lower than reported for the C2v geometry.

Correction: The applicability of proton transfer reaction-mass spectrometry (PTR-MS) for determination of isocyanic acid (ICA) in work room atmospheres.

Correction for 'The applicability of proton transfer reaction-mass spectrometry (PTR-MS) for determination of isocyanic acid (ICA) in work room atmospheres' by Mikolaj Jan Jankowski et al., Environ. Sci.: Processes Impacts, 2014, 16, 2423-2431.

The applicability of proton transfer reaction-mass spectrometry (PTR-MS) for determination of isocyanic acid (ICA) in work room atmospheres.

A method is presented for the real-time quantitative determination of isocyanic acid (ICA) in air using proton transfer reaction-mass spectrometry (PTR-MS). Quantum mechanical calculations were performed to establish the ion-polar molecule reaction rate of ICA and other isocyanates. The PTR-MS was calibrated against different ICA air concentrations and humidity conditions using Fourier transform-infrared spectroscopy (FT-IR) as quantitative reference. Based on these experiments a simple humidity dependant model was derived for correction of the PTR-MS response for ICA. The corrected PTR-MS data was linearly correlated (R(2) > 0.99) with the data acquired by FT-IR. The PTR-MS instrumental limit of detection (LOD) for ICA was 2.3 ppb. Humid atmospheres resulted in LODs of 3.4 and 7.8 ppb, at an absolute humidity (AH) of 4.0 and 15.5 g m(-3), respectively. Furthermore, off-line sampling using denuder and impinger samplers using di-n-butylamine (DBA) as derivatization reagent was compared with PTR-MS measurements in a dynamically generated standard ICA atmosphere. Denuder (n = 4) and impinger (n = 4) sampling subsequent to liquid chromatography mass spectrometry (LC-MS) determination compared to corrected PTR-MS data resulted in recoveries of 79.6 (8.1% RSD) and 99.9 (9.3% RSD) %, respectively. Measurements of ICA from thermally decomposed cured 1,6-hexamethylene diisocyanate (HDI)-paint was performed using PTR-MS and denuder (n = 3) sampling. The relation between the average ICA responses using denuders (34.4 ppb) and PTR-MS (42.6 ppb) was 80.6%, which coincided well with the relative recovery obtained from the controlled laboratory experiments using dynamically generated ICA atmospheres (79.6%). The variability in ICA air concentration during the welding process (170% RSDPTR-MS) illustrated the need for real-time measurements.

Atmospheric fate of nitramines: an experimental and theoretical study of the OH reactions with CH3NHNO2 and (CH3)2NNO2.

The rates of CH3NHNO2 and (CH3)2NNO2 reaction with OH radicals were determined relative to CH3OCH3 and CH3OH at 298 ± 2 K and 1013 ± 10 hPa in purified air by long path FTIR spectroscopy, and the rate coefficients were determined to be k(OH+CH3NHNO2) = (9.5 ± 1.9) × 10(-13) and k(OH+(CH3)2NNO2) = (3.5 ± 0.7) × 10(-12) (2σ) cm(3) molecule(-1) s(-1). Ozone was found to react very slowly with the two nitramines, k(O3+nitramine) < 10(-21) cm(3) molecule(-1) s(-1). Product formation in the photo-oxidation of CH3NHNO2 and (CH3)2NNO2 was studied by FTIR, PTR-ToF-MS, and quantum chemistry calculations; the major products in the OH-initiated degradation are the corresponding imines, CH2═NH and CH3N═CH2, and N-nitro amides, CHONHNO2 and CHON(CH3)NO2. Atmospheric degradation mechanisms are presented.

Real-time monitoring of emissions from monoethanolamine-based industrial scale carbon capture facilities.

We demonstrate the capabilities and properties of using Proton Transfer Reaction time-of-flight mass spectrometry (PTR-ToF-MS) to real-time monitor gaseous emissions from industrial scale amine-based carbon capture processes. The benchmark monoethanolamine (MEA) was used as an example of amines needing to be monitored from carbon capture facilities, and to describe how the measurements may be influenced by potentially interfering species in CO2 absorber stack discharges. On the basis of known or expected emission compositions, we investigated the PTR-ToF-MS MEA response as a function of sample flow humidity, ammonia, and CO2 abundances, and show that all can exhibit interferences, thus making accurate amine measurements difficult. This warrants a proper sample pretreatment, and we show an example using a dilution with bottled zero air of 1:20 to 1:10 to monitor stack gas concentrations at the CO2 Technology Center Mongstad (TCM), Norway. Observed emissions included many expected chemical species, dominantly ammonia and acetaldehyde, but also two new species previously not reported but emitted in significant quantities. With respect to concerns regarding amine emissions, we show that accurate amine quantifications in the presence of water vapor, ammonia, and CO2 become feasible after proper sample dilution, thus making PTR-ToF-MS a viable technique to monitor future carbon capture facility emissions, without conventional laborious sample pretreatment.

Theoretical study on the formation and photolysis of nitrosamines (CH3CH2NHNO and (CH3CH2)2NNO) under atmospheric conditions.

The reactions of CH(3)CH(2)NH and (CH(3)CH(2))(2)N radicals with NO have been studied using quantum chemistry methods. The results show that formation of the nitrosamines CH(3)CH(2)NHNO and (CH(3)CH(2))(2)NNO is similar and that both isolated molecules are thermally stable. The nitrosamine formation reaction is highly exothermic, and the hot CH(3)CH(2)NHNO may undergo isomerization and subsequent reaction with O(2) to form the corresponding imine, CH(3)CH═NH. Time-dependent density functional theory (TDDFT) calculations show little difference of the vertical excitation energy between the π* ← n transitions in CH(3)CH(2)NHNO and (CH(3)CH(2))(2)NNO, and both will readily photolyze under sunlight conditions.

Do primary nitrosamines form and exist in the gas phase? A computational study of CH3NHNO and (CH3)2NNO.

The reactions of the CH(3)NH and (CH(3))(2)N radicals with NO have been studied using quantum chemistry methods to compare the formation and stability of primary and secondary nitrosamines. The calculations show that the entrance part of potential energy surfaces of CH(3)NHNO and (CH(3))(2)NNO formation are similar, and it is concluded that primary amines form nitrosamines under the atmospheric conditions. CH(3)NHNO can, in contrast to (CH(3))(2)NNO, undergo isomerization via a barrier below the reactants entrance energy to CH(2)NHNOH, which through reaction with O(2) eventually leads to formation of CH(2)=NH on a short timescale. TDDFT, CASPT2 and MR-CI calculations show little difference between the n→π* transitions in CH(3)NHNO and (CH(3))(2)NNO and that the two molecules should have comparable photolysis lifetimes in the atmosphere.

Spectral shifts of matrix isolated species as criteria for acid-base interactions with solid Xe.

The vibrational spectra of H(2)SO(4)/H(2)O vapors trapped in solid Xe are reported and the spectral shifts are compared to the analogous spectra in argon matrices. In the same matrix layer the nu(OH) stretches of highly acidic species (H(2)SO(4) and H(2)SO(4)*H(2)O) show distinctly larger red shifts as opposed to species of lower acidity or to modes which do not involve directly the O-H bond. A correlation is obtained of the spectral shifts with energies empirically estimated from acidic properties attributed to a variety of molecular species. The hydrogen bonding observed between acidic species and Xe atoms is considered relevant to the formation of xenon hydrides in irradiated matrices. The spectral interpretation is complemented by B3LYP and MP2 calculations of the interaction energies and fundamental modes of vibration.