Rate coefficients and product branching measurements for the reaction OH + bromopropane from 230 to 360 K

Article on rate coefficient and product branching measurements for the reaction OH + bromopropane from 230 to 360 K

Seniorzy w społeczeństwie XXI wieku. Materiały konferencyjne III Galicyjskich Spotkań Medycznych

Z przedmowy: "Naturalną koleją rzeczy wszyscy ku niej zmierzamy. Starość jest równie nieuchronna jak kolejna pora roku. A jednak na co dzień wolimy o niej nie myśleć, nie lubimy o niej mówić. W dzisiejszym świecie, kiedy liczy się przede wszystkim młodość, powodzenie, osobisty sukces, starość zazwyczaj kojarzy się z odchodzeniem na margines życia, dolegliwościami ciała, z samotnością. Czas mija, a my łudzimy się, że mija dla innych, nie dla nas, że my sami nadal jesteśmy młodzi. Aż pewnego dnia nieoczekiwanie jakiś dobrze wychowany młody człowiek z wymownym spojrzeniem ustępuje nam miejsca w tramwaju... Jak godzimy się z upływem czasu, co robimy, żeby przygotować się do tego, jacy będziemy za kilka, kilkanaście, kilkadziesiąt lat, żebyśmy nie czuli się zaskoczeni, żeby nie pozostało nam tylko gorzkie „a nie mówiłem” i poczucie zmarnowanych życiowych szans? Jak dziś odnosimy się do naszych seniorów w rodzinach, w najbliższym otoczeniu, w społeczeństwie, do którego należymy? Stoi przed nami wiele trudnych zadań."(...

<i>cis-</i>Pinonic Acid Oxidation by Hydroxyl Radicals in the Aqueous Phase under Acidic and Basic Conditions: Kinetics and Mechanism

Aqueous-phase oxidation of <i>cis-</i>pinonic acid (CPA) by hydroxyl radicals (OH) was studied using a relative rate technique under acidic and basic conditions. Liquid chromatography (LC) coupled to the negative electrospray ionization (ESI) quadrupole tandem mass spectrometry (MS/MS) was used to monitor the concentrations of CPA and reference compounds. The measured second order reaction rate coefficients of CPA with OH were: 3.6 ± 0.3 × 10⁹ M^–1 s^–1 (pH 2) and 3.0 ± 0.3 × 10⁹ M^–1 s^–1 (pH 10) - combined uncertainties are 2σ. These results indicated that the lifetimes of CPA in the atmosphere are most likely independent from the aqueous-phase pH. LC-ESI/MS/MS was also used to tentatively identify the CPA oxidation products. Formation of carboxylic acids with molecular weight (MW) 216 Da (most likely C₁₀H₁₆O₅) and MW 214 Da (C₁₀H₁₄O₅) was confirmed with LC-ESI/MS/MS. When the initial CPA concentration was increased from 0.3 to 10 mM, formation of additional products was observed with MW 188, 200, 204, and 232 Da. Hydroperoxy, hydroxyl and carbonyl-substituted CPA derivatives were tentatively identified among the products. Similar products were formed by the CPA oxidation by OH in the gas-phase, at the air–water interface as well as in the solid phase (dry film). Formation of the stable adduct of CPA and H₂O₂ was also observed when the reaction mixture was evaporated to dryness and redissolved in water. Acquired mass spectrometric data argues against formation of oligomers

Investigation of nucleation thresholds in the reactions of ozone with Volatile Organic Compounds (VOCs)

International audienc

Rate coefficients for the reactions of hydroxyl radical with Cl2O, OClO and HClO

International audienc

Investigation of nucleation thresholds in the reactions of ozone with Volatile Organic Compounds (VOCs)

International audienc

OH + (<i>E</i>)- and (<i>Z</i>)‑1-Chloro-3,3,3-trifluoropropene‑1 (CF₃CHCHCl) Reaction Rate Coefficients: Stereoisomer-Dependent Reactivity

Rate coefficients for the gas-phase reaction of the OH radical with (<i>E</i>)- and (<i>Z</i>)-CF₃CHCHCl (1-chloro-3,3,3-trifluoropropene-1, HFO-1233zd) (<i>k</i>₁(<i>T</i>) and <i>k</i>₂(<i>T</i>), respectively) were measured under pseudo-first-order conditions in OH over the temperature range 213–376 K. OH was produced by pulsed laser photolysis, and its temporal profile was measured using laser-induced fluorescence. The obtained rate coefficients were independent of pressure between 25 and 100 Torr (He, N₂) with <i>k</i>₁(296 K) = (3.76 ± 0.35) × 10^–13 cm³ molecule^–1 s^–1 and <i>k</i>₂(296 K) = (9.46 ± 0.85) × 10^–13 cm³ molecule^–1 s^–1 (quoted uncertainties are 2σ and include estimated systematic errors). <i>k</i>₂(<i>T</i>) showed a weak non-Arrhenius behavior over this temperature range. The (<i>E</i>)- and (<i>Z</i>)- stereoisomer rate coefficients were found to have opposite temperature dependencies that are well represented by <i>k</i>₁(<i>T</i>) = (1.14 ± 0.15) × 10^–12 exp[(−330 ± 10)/<i>T</i>] cm³ molecule^–1 s^–1 and <i>k</i>₂(<i>T</i>) = (7.22 ± 0.65) × 10^–19 × <i>T</i>² × exp[(800 ± 20)/<i>T</i>] cm³ molecule^–1 s^–1. The present results are compared with a previous room temperature relative rate coefficient study of <i>k</i>₁, and an explanation for the discrepancy is presented. CF₃CHO, HC­(O)­Cl, and CF₃CClO, were observed as stable end-products following the OH radical initiated degradation of (<i>E</i>)- and (<i>Z</i>)-CF₃CHCHCl in the presence of O₂. In addition, chemically activated isomerization was also observed. Atmospheric local lifetimes of (<i>E</i>)- and (<i>Z</i>)-CF₃CHCHCl, due to OH reactive loss, were estimated to be ∼34 and ∼11 days, respectively. Infrared absorption spectra measured in this work were used to estimate radiative efficiencies and well-mixed global warming potentials of ∼10 and ∼3 for (<i>E</i>)- and (<i>Z</i>)-CF₃CHCHCl, respectively, on the 100-year time horizon