scholarly journals Synthesis of methanediol [CH2(OH)2]: The simplest geminal diol

2021 ◽  
Vol 119 (1) ◽  
pp. e2111938119
Author(s):  
Cheng Zhu ◽  
N. Fabian Kleimeier ◽  
Andrew M. Turner ◽  
Santosh K. Singh ◽  
Ryan C. Fortenberry ◽  
...  
Keyword(s):  
Gas Phase ◽  
Atmospheric Chemistry ◽  
Reactive Intermediates ◽  
Hydroxyl Groups ◽  
Unimolecular Decomposition ◽  
Flight Mass Spectrometry ◽  
Criegee Intermediates ◽  
Aldehydes And Ketones ◽  
Electronically Excited ◽  
Geminal Diol

Geminal diols—organic molecules carrying two hydroxyl groups at the same carbon atom—have been recognized as key reactive intermediates by the physical (organic) chemistry and atmospheric science communities as fundamental transients in the aerosol cycle and in the atmospheric ozonolysis reaction sequence. Anticipating short lifetimes and their tendency to fragment to water plus the aldehyde or ketone, free geminal diols represent one of the most elusive classes of organic reactive intermediates. Here, we afford an exceptional glance into the preparation of the previously elusive methanediol [CH2(OH)2] transient—the simplest geminal diol—via energetic processing of low-temperature methanol–oxygen ices. Methanediol was identified in the gas phase upon sublimation via isomer-selective photoionization reflectron time-of-flight mass spectrometry combined with isotopic substitution studies. Electronic structure calculations reveal that methanediol is formed via excited state dynamics through insertion of electronically excited atomic oxygen into a carbon–hydrogen bond of the methyl group of methanol followed by stabilization in the icy matrix. The first preparation and detection of methanediol demonstrates its gas-phase stability as supported by a significant barrier hindering unimolecular decomposition to formaldehyde and water. These findings advance our perception of the fundamental chemistry and chemical bonding of geminal diols and signify their role as an efficient sink of aldehydes and ketones in atmospheric environments eventually coupling the atmospheric chemistry of geminal diols and Criegee intermediates.

scholarly journals Evaluated kinetic and photochemical data for atmospheric chemistry: Volume VII – Criegee intermediates

2020 ◽  
Vol 20 (21) ◽  
pp. 13497-13519
Author(s):  
R. Anthony Cox ◽  
Markus Ammann ◽  
John N. Crowley ◽  
Hartmut Herrmann ◽  
Michael E. Jenkin ◽  
...  
Keyword(s):  
Gas Phase ◽  
Atmospheric Chemistry ◽  
Kinetic Data ◽  
Chemical Kinetic ◽  
Photochemical Reactions ◽  
Task Group ◽  
Rate Coefficients ◽  
Laboratory Measurements ◽  
Bimolecular Reactions ◽  
Criegee Intermediates

Abstract. This article, the seventh in the series, presents kinetic and photochemical data sheets evaluated by the IUPAC Task Group on Atmospheric Chemical Kinetic Data Evaluation. It covers an extension of the gas-phase and photochemical reactions related to Criegee intermediates previously published in Atmospheric Chemistry and Physics (ACP) in 2006 and implemented on the IUPAC website up to 2020. The article consists of an introduction, description of laboratory measurements, a discussion of rate coefficients for reactions of O3 with alkenes producing Criegee intermediates, rate coefficients of unimolecular and bimolecular reactions and photochemical data for reactions of Criegee intermediates, and an overview of the atmospheric chemistry of Criegee intermediates. Summary tables of the recommended kinetic and mechanistic parameters for the evaluated reactions are provided. Data sheets summarizing information upon which the recommendations are based are given in two files, provided as a Supplement to this article.

The origin of light emission in the atomic hydrogen—acetylene flame

1964 ◽  
Vol 282 (1389) ◽  
pp. 275-282 ◽  
Keyword(s):  
Gas Phase ◽  
Atomic Hydrogen ◽  
Atomic Oxygen ◽  
Light Emission ◽  
Reactive Intermediates ◽  
Hydrogen Atoms ◽  
Electronically Excited ◽  
Catalytic Recombination ◽  
Oxygen Atoms

Acetylene catalyzes the gas phase recombination of hydrogen atoms, and frequently the reaction is accompanied by a bright flame. It is shown that the light emission is not the result of the catalytic recombination, but is caused by traces of water in the hydrogen. The possible reactive intermediates, OH, HO 2 and atomic oxygen, have been individually generated and added to the mixture of hydrogen atoms and acetylene. Only oxygen atoms are effective in causing luminescence. Hydrogen atoms are not necessary for light emission, but they do alter the spectrum somewhat. Two different mechanisms for the formation of electronically excited C 2 are required. The mechanism for the reaction of atomic oxygen with acetylene is discussed.

High resolution absolute absorption cross sections of the B̃1A′–X̃1A′ transition of the CH2OO biradical

2015 ◽  
Vol 17 (48) ◽  
pp. 32539-32546 ◽  
Author(s):  
Elizabeth S. Foreman ◽  
Kara M. Kapnas ◽  
YiTien Jou ◽  
Jarosław Kalinowski ◽  
David Feng ◽  
...  
Keyword(s):  
High Resolution ◽  
Gas Phase ◽  
Urban Area ◽  
Cross Sections ◽  
Atmospheric Chemistry ◽  
Pivotal Role ◽  
Absorption Cross ◽  
Night Time ◽  
Carbonyl Oxides ◽  
Criegee Intermediates

Carbonyl oxides, or Criegee intermediates, are formed from the gas phase ozonolysis of alkenes and play a pivotal role in night-time and urban area atmospheric chemistry.

scholarly journals Evaluated kinetic and photochemical data for atmospheric chemistry: Volume VII – Criegee intermediates

2020 ◽  
Author(s):  
R. Anthony Cox ◽  
Markus Ammann ◽  
John N. Crowley ◽  
Hartmut Herrmann ◽  
Michael E. Jenkin ◽  
...  
Keyword(s):  
Gas Phase ◽  
Atmospheric Chemistry ◽  
Kinetic Data ◽  
Chemical Kinetic ◽  
Photochemical Reactions ◽  
Task Group ◽  
Rate Coefficients ◽  
Laboratory Measurements ◽  
Bimolecular Reactions ◽  
Criegee Intermediates

Abstract. This article, the seventh in the series, presents kinetic and photochemical data sheets evaluated by the IUPAC Task Group on Atmospheric Chemical Kinetic Data Evaluation. It covers an extension of the gas phase and photochemical reactions related to Criegee intermediates previously published in ACP in 2006, and implemented on the IUPAC website up to 2020. The article consists of an introduction, description of laboratory measurements, discussion of rate coefficients for reactions of O3 with alkenes producing Criegee intermediates, rate coefficients of unimolecular and bimolecular reactions and photochemical data for reactions of Criegee intermediates, and overview of the atmospheric chemistry of Criegee intermediates. Summary tables of the recommended kinetic and mechanistic parameters for the evaluated reactions are provided. Data sheets summarizing information upon which the recommendations are based are given in two files, provided as a Supplement to this article.

A vibrational spectroscopic and computational study of the structures of protonated imidacloprid and its fragmentation products in the gas phase

2021 ◽  
Vol 23 (5) ◽  
pp. 3377-3388
Author(s):  
Kelsey J. Menard ◽  
Jonathan Martens ◽  
Travis D. Fridgen
Keyword(s):  
Computational Chemistry ◽  
Gas Phase ◽  
Vibrational Spectroscopy ◽  
Computational Study ◽  
Unimolecular Decomposition ◽  
Decomposition Products

Vibrational spectroscopy and computational chemistry studies were combined with the aim of elucidating the structures of protonated imidacloprid (pIMI), and its unimolecular decomposition products.

scholarly journals Application of random forest regression to the calculation of gas-phase chemistry within the GEOS-Chem chemistry model v10

2019 ◽  
Vol 12 (3) ◽  
pp. 1209-1225 ◽  
Author(s):  
Christoph A. Keller ◽  
Mat J. Evans
Keyword(s):  
Machine Learning ◽  
Random Forest ◽  
Gas Phase ◽  
Atmospheric Chemistry ◽  
Random Forest Regression ◽  
Data Set ◽  
Gas Phase Chemistry ◽  
Chemical Conditions ◽  
Phase Chemistry ◽  
The Impact

Abstract. Atmospheric chemistry models are a central tool to study the impact of chemical constituents on the environment, vegetation and human health. These models are numerically intense, and previous attempts to reduce the numerical cost of chemistry solvers have not delivered transformative change. We show here the potential of a machine learning (in this case random forest regression) replacement for the gas-phase chemistry in atmospheric chemistry transport models. Our training data consist of 1 month (July 2013) of output of chemical conditions together with the model physical state, produced from the GEOS-Chem chemistry model v10. From this data set we train random forest regression models to predict the concentration of each transported species after the integrator, based on the physical and chemical conditions before the integrator. The choice of prediction type has a strong impact on the skill of the regression model. We find best results from predicting the change in concentration for long-lived species and the absolute concentration for short-lived species. We also find improvements from a simple implementation of chemical families (NOx = NO + NO2). We then implement the trained random forest predictors back into GEOS-Chem to replace the numerical integrator. The machine-learning-driven GEOS-Chem model compares well to the standard simulation. For ozone (O3), errors from using the random forests (compared to the reference simulation) grow slowly and after 5 days the normalized mean bias (NMB), root mean square error (RMSE) and R2 are 4.2 %, 35 % and 0.9, respectively; after 30 days the errors increase to 13 %, 67 % and 0.75, respectively. The biases become largest in remote areas such as the tropical Pacific where errors in the chemistry can accumulate with little balancing influence from emissions or deposition. Over polluted regions the model error is less than 10 % and has significant fidelity in following the time series of the full model. Modelled NOx shows similar features, with the most significant errors occurring in remote locations far from recent emissions. For other species such as inorganic bromine species and short-lived nitrogen species, errors become large, with NMB, RMSE and R2 reaching >2100 % >400 % and <0.1, respectively. This proof-of-concept implementation takes 1.8 times more time than the direct integration of the differential equations, but optimization and software engineering should allow substantial increases in speed. We discuss potential improvements in the implementation, some of its advantages from both a software and hardware perspective, its limitations, and its applicability to operational air quality activities.

A Combined Experimental and Theoretical Study of the Homogeneous, Unimolecular Decomposition Kinetics of 3-Chloropivalic Acid in the Gas Phase

2001 ◽  
Vol 105 (10) ◽  
pp. 1869-1875 ◽  
Author(s):  
Gabriel Chuchani ◽  
Alexandra Rotinov ◽  
Juan Andrés ◽  
Luís R. Domingo ◽  
V. Sixte Safont
Keyword(s):  
Gas Phase ◽  
Theoretical Study ◽  
Decomposition Kinetics ◽  
Unimolecular Decomposition ◽  
Kinetics Of

Atmospheric chemistry of trans-CF3CHCHCl: Kinetics of the gas-phase reactions with Cl atoms, OH radicals, and O3

2008 ◽  
Vol 199 (1) ◽  
pp. 92-97 ◽  
Author(s):  
M.P. Sulbaek Andersen ◽  
E.J.K. Nilsson ◽  
O.J. Nielsen ◽  
M.S. Johnson ◽  
M.D. Hurley ◽  
...  
Keyword(s):  
Gas Phase ◽  
Atmospheric Chemistry ◽  
Oh Radicals ◽  
Gas Phase Reactions ◽  
Kinetics Of ◽  
Cl Atoms

Newly developed instrumentation for measuring highly oxidized molecules at atmospheric pressure

2021 ◽  
Author(s):  
Paap Koemets ◽  
Sander Mirme ◽  
Kuno Kooser ◽  
Heikki Junninen
Keyword(s):  
Gas Phase ◽  
Atmospheric Chemistry ◽  
Atmospheric Pressure ◽  
Chemical Ionization ◽  
Measurement Technology ◽  
Differential Mobility Analyzer ◽  
Neutral Cluster ◽  
Differential Mobility ◽  
Alpha Pinene ◽  
Ambient Measurements

&lt;p&gt;The Highly Oxidized Molecule Ion Spectrometer (HOMIS) is a novel instrument for measuring the total concentration of highly oxidized molecules (HOM-s) (Bianchi et al., 2019) at atmospheric pressure. The device combines a chemical ionization charger with a multi-channel differential mobility analyzer. The chemical ionization charger is based on the principles outlined by Eisele and Tanner (1993). The charger is attached to a parallel differential mobility analyzer identical to the ones used in the Neutral cluster and Air Ion Spectrometer (NAIS, Mirme 2011), but with modified sample and sheath air flow rates to improve the mobility resolution of the device. The complete mobility distribution in the range from 3.2 to 0.056 cm&lt;sup&gt;2&lt;/sup&gt;/V/s is measured simultaneously by 25 electrometers. The range captures the charger ions, monomers, dimers, trimers but also extends far towards larger particles to possibly detect larger HOM-s that have not been measured with existing instrumentation. The maximum time resolution of the device is 1 second allowing it to detect rapid changes in the sample. The device has been designed to be easy to use, require little maintenance and work reliably in various environments during long term measurements.&lt;/p&gt;&lt;p&gt;First results of the prototype were acquired from laboratory experiments and ambient measurements. Experiments were conducted at the Laboratory of Environmental Physics, University of Tartu. The sample was drawn from a reaction chamber where alpha-pinene and ozone were introduced. Initial results show a good response when concentrations of alpha-pinene and ozone were changed.&amp;#160;&lt;/p&gt;&lt;p&gt;Ambient measurements were conducted at the SMEAR Estonia measurement station in a hemiboreal forest for 10 days in the spring and two months in the winter of 2020. The HOMIS measurements were performed together with a CI-APi-TOF (Jokinen et al., 2012).&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;References:&lt;/p&gt;&lt;p&gt;Bianchi, F., Kurt&amp;#233;n, T., Riva, M., Mohr, C., Rissanen, M. P., Roldin, P., Berndt, T., Crounse, J. D., Wennberg, P. O., Mentel, T. F., Wildt, J., Junninen, H., Jokinen, T., Kulmala, M., Worsnop, D. R., Thornton, J. A., Donahue, N., Kjaergaard, H. G. and Ehn, M. (2019), &amp;#8220;Highly Oxygenated Organic Molecules (HOM) from Gas-Phase Autoxidation Involving Peroxy Radicals: A Key Contributor to Atmospheric Aerosol&amp;#8221;, Chemical Reviews, 119, 6, 3472&amp;#8211;3509&lt;/p&gt;&lt;p&gt;Eisele, F. L., Tanner D. J. (1993), &amp;#8220;Measurement of the gas phase concentration of H2SO4 and methane sulfonic acid and estimates of H2SO4 production and loss in the atmosphere&amp;#8221;, JGR: Atmospheres, 98, 9001-9010&lt;/p&gt;&lt;p&gt;Jokinen T., Sipil&amp;#228; M., Junninen H., Ehn M., L&amp;#246;nn G., Hakala J., Pet&amp;#228;j&amp;#228; T., Mauldin III R. L., Kulmala M., and Worsnop D. R. (2012), &amp;#8220;Atmospheric sulphuric acid and neutral cluster measurements using CI-APi-TOF&amp;#8221;, Atmospheric Chemistry and Physics, 12, 4117&amp;#8211;4125&lt;/p&gt;&lt;p&gt;Mirme, S. (2011), &amp;#8220;Development of nanometer aerosol measurement technology&amp;#8221;, Doctoral thesis, University of Tartu&lt;/p&gt;

scholarly journals Reactive quenching of electronically excited NO<sub>2</sub><sup>∗</sup> and NO<sub>3</sub><sup>∗</sup> by H<sub>2</sub>O as potential sources of atmospheric HO<sub><i>x</i></sub> radicals

2018 ◽  
Vol 18 (19) ◽  
pp. 14005-14015 ◽  
Author(s):  
Terry J. Dillon ◽  
John N. Crowley
Keyword(s):  
Gas Phase ◽  
Laser Excitation ◽  
Pulsed Laser ◽  
Work Rate ◽  
Rate Coefficients ◽  
Phase Reaction ◽  
Gas Phase Reaction ◽  
Upper Limit ◽  
Upper Limits ◽  
Electronically Excited

Abstract. Pulsed laser excitation of NO2 (532–647 nm) or NO3 (623–662 nm) in the presence of H2O was used to initiate the gas-phase reaction NO2∗+H2O → products (Reaction R5) and NO3∗+H2O → products (Reaction R12). No evidence for OH production in Reactions (R5) or (R12) was observed and upper limits for OH production of k5b/k5<1×10-5 and k12b/k12<0.03 were assigned. The upper limit for k5b∕k5 renders this reaction insignificant as a source of OH in the atmosphere and extends the studies (Crowley and Carl, 1997; Carr et al., 2009; Amedro et al., 2011) which demonstrate that the previously reported large OH yield by Li et al. (2008) was erroneous. The upper limit obtained for k12b∕k12 indicates that non-reactive energy transfer is the dominant mechanism for Reaction (R12), though generation of small but significant amounts of atmospheric HOx and HONO cannot be ruled out. In the course of this work, rate coefficients for overall removal of NO3∗ by N2 (Reaction R10) and by H2O (Reaction R12) were determined: k10=(2.1±0.1)×10-11 cm3 molecule−1 s−1 and k12=(1.6±0.3)×10-10 cm3 molecule−1 s−1. Our value of k12 is more than a factor of 4 smaller than the single previously reported value.

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