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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 × 10<sup>9</sup> M<sup>–1</sup> s<sup>–1</sup> (pH 2) and 3.0 ± 0.3 × 10<sup>9</sup> M<sup>–1</sup> s<sup>–1</sup> (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 C<sub>10</sub>H<sub>16</sub>O<sub>5</sub>) and
MW 214 Da (C<sub>10</sub>H<sub>14</sub>O<sub>5</sub>) 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 H<sub>2</sub>O<sub>2</sub> 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
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
OH + (<i>E</i>)- and (<i>Z</i>)‑1-Chloro-3,3,3-trifluoropropene‑1 (CF<sub>3</sub>CHCHCl) 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>)-CF<sub>3</sub>CHCHCl (1-chloro-3,3,3-trifluoropropene-1, HFO-1233zd) (<i>k</i><sub>1</sub>(<i>T</i>) and <i>k</i><sub>2</sub>(<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, N<sub>2</sub>) with <i>k</i><sub>1</sub>(296 K) = (3.76 ± 0.35)
× 10<sup>–13</sup> cm<sup>3</sup> molecule<sup>–1</sup> s<sup>–1</sup> and <i>k</i><sub>2</sub>(296 K)
= (9.46 ± 0.85) × 10<sup>–13</sup> cm<sup>3</sup> molecule<sup>–1</sup> s<sup>–1</sup> (quoted uncertainties
are 2σ and include estimated systematic errors). <i>k</i><sub>2</sub>(<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><sub>1</sub>(<i>T</i>) = (1.14 ± 0.15) × 10<sup>–12</sup> exp[(−330 ± 10)/<i>T</i>]
cm<sup>3</sup> molecule<sup>–1</sup> s<sup>–1</sup> and <i>k</i><sub>2</sub>(<i>T</i>) = (7.22 ± 0.65) ×
10<sup>–19</sup> × <i>T</i><sup>2</sup> ×
exp[(800 ± 20)/<i>T</i>] cm<sup>3</sup> molecule<sup>–1</sup> s<sup>–1</sup>. The present results are compared
with a previous room temperature relative rate coefficient study of <i>k</i><sub>1</sub>, and an explanation for the discrepancy is
presented. CF<sub>3</sub>CHO, HC(O)Cl, and CF<sub>3</sub>CClO, were
observed as stable end-products following the OH radical initiated
degradation of (<i>E</i>)- and (<i>Z</i>)-CF<sub>3</sub>CHCHCl in the presence of O<sub>2</sub>. In addition,
chemically activated isomerization was also observed. Atmospheric
local lifetimes of (<i>E</i>)- and (<i>Z</i>)-CF<sub>3</sub>CHCHCl, 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>)-CF<sub>3</sub>CHCHCl,
respectively, on the 100-year time horizon