scholarly journals Kinetics of the reactions of isoprene-derived hydroxynitrates: gas phase epoxide formation and solution phase hydrolysis

2014 ◽  
Vol 14 (17) ◽  
pp. 8933-8946 ◽  
Author(s):  
M. I. Jacobs ◽  
W. J. Burke ◽  
M. J. Elrod
Keyword(s):  
Gas Phase ◽  
Hydrolysis Rate ◽  
Ionization Mass ◽  
Volatile Organic ◽  
Isoprene Oxidation ◽  
Gas Phase Oxidation ◽  
Acid Catalyzed ◽  
Regional Formation ◽  
A Minor ◽  
Kinetics Of

Abstract. Isoprene, the most abundant non-methane volatile organic compound (VOC) emitted into the atmosphere, is known to undergo gas phase oxidation to form eight different hydroxynitrate isomers in "high-NOx" environments. These hydroxynitrates are known to affect the global and regional formation of ozone and secondary organic aerosol (SOA), as well as affect the distribution of nitrogen. In the present study, we have synthesized three of the eight possible hydroxynitrates: 4-hydroxy-3-nitroxy isoprene (4,3-HNI) and E / Z-1-hydroxy-4-nitroxy isoprene (1,4-HNI). Oxidation of the 4,3-HNI isomer by the OH radical was monitored using a flow tube chemical ionization mass spectrometer (FT-CIMS), and its OH rate constant was determined to be (3.64 ± 0.41) × 10−11 cm3 molecule−1 s−1. The products of 4,3-HNI oxidation were monitored, and a mechanism to explain the products was developed. An isoprene epoxide (IEPOX) – a species important in SOA chemistry and thought to originate only from "low-NOx" isoprene oxidation – was found as a minor, but significant, product. Additionally, hydrolysis kinetics of the three synthesized isomers were monitored with nuclear magnetic resonance (NMR). The bulk, neutral solution hydrolysis rate constants for 4,3-HNI and the 1,4-HNI isomers were (1.59 ± 0.03) × 10−5 s−1 and (6.76 ± 0.09) × 10−3 s−1, respectively. The hydrolysis reactions of each isomer were found to be general acid-catalyzed. The reaction pathways, product yields and atmospheric implications for both the gas phase and aerosol phase reactions are discussed.

scholarly journals Kinetics of the reactions of isoprene-derived hydroxynitrates: gas phase epoxide formation and solution phase hydrolysis

2014 ◽  
Vol 14 (8) ◽  
pp. 12121-12165 ◽  
Author(s):  
M. I. Jacobs ◽  
W. J. Burke ◽  
M. J. Elrod
Keyword(s):  
Gas Phase ◽  
Hydrolysis Rate ◽  
Ionization Mass ◽  
Volatile Organic ◽  
Isoprene Oxidation ◽  
Gas Phase Oxidation ◽  
Acid Catalyzed ◽  
Regional Formation ◽  
A Minor ◽  
Kinetics Of

Abstract. Isoprene, the most abundant non-methane volatile organic compound (VOC) emitted into the atmosphere, is known to undergo gas phase oxidation to form eight different hydroxynitrate isomers in "high NOx" environments. These hydroxynitrates are known to affect the global and regional formation of ozone and secondary organic aerosol (SOA), as well as affect the distribution of nitrogen. In the present study, we have synthesized three of the eight possible hydroxynitrates: 4-hydroxy-3-nitroxy isoprene (4,3-HNI) and E/Z-1-hydroxy-4-nitroxy isoprene (1,4-HNI). Oxidation of the 4,3-HNI isomer by the OH radical was monitored using a flow tube chemical ionization mass spectrometer (FT-CIMS), and its OH rate constant was determined to be (3.64 ± 0.41) × 10−11 cm3 molecule−1 s−1. The products of 4,3-HNI oxidation were monitored, and a mechanism to explain the products was developed. An isoprene epoxide (IEPOX) – a species important in SOA chemistry and thought to originate only from "low NOx" isoprene oxidation – was found as a minor, but significant product. Additionally, hydrolysis kinetics of the three synthesized isomers were monitored with NMR. The bulk, neutral solution hydrolysis rate constants for 4,3-HNI and the 1,4-HNI isomers were (1.59±0.03 × 10−5 s−1 and (6.76 ± 0.09) × 10−3 s−1, respectively. The hydrolysis reactions of each isomer were found to be general acid-catalyzed. The reaction pathways, product yields and atmospheric implications for both the gas phase and aerosol-phase reactions are discussed.

New Insights into the Kinetics of the Gas-Phase Oxidation of Hexafluoropropene

2016 ◽  
Vol 41 (4) ◽  
pp. 418-427 ◽  
Author(s):  
David Lokhat ◽  
Maciej Starzak ◽  
Deresh Ramjugernath
Keyword(s):  
Gas Phase ◽  
Oxidation Process ◽  
Flow Reactor ◽  
Packed Column ◽  
Phase Reaction ◽  
Analytical Technique ◽  
Tubular Flow Reactor ◽  
Gas Phase Oxidation ◽  
Tubular Flow ◽  
Kinetics Of

The gas-phase reaction of hexafluoropropene and molecular oxygen was investigated in a tubular flow reactor at 450 kPa and within a temperature range of 463–493 K using HFP/O2 mixtures containing 20–67% HFP on a molar basis. Capillary and packed column chromatography served as the main analytical technique. The reaction yielded HFPO, COF2, CF3COF, C2F4 and c-C3F6 as gas-phase products. High molecular weight oligomers were also formed. The oligomers were found to have a polyoxadifluoromethylene structure according to elemental and 19F NMR analysis. At 493 K HFP is proposed to undergo oxygen-mediated decomposition to difluorocarbene radicals, yielding greater quantities of difluorocarbene recombination products. Kinetic parameters for a revised model of the oxidation process were identified through least squares analysis of the experimental data.

Effect of surface on the gas-phase oxidation of methanol catalysed by nitric oxide

1964 ◽  
Vol 17 (5) ◽  
pp. 539
Author(s):  
JJ Batten
Keyword(s):  
Nitric Oxide ◽  
Gas Phase ◽  
Marked Effect ◽  
Volume Ratio ◽  
Oxidation Of Methanol ◽  
Inorganic Substances ◽  
Phase Oxidation ◽  
Gas Phase Oxidation ◽  
Kinetics Of ◽  
Effect Of Surface

A study has been made of the effect of the surface-to-volume ratio of the reaction vessel and of coatings of various inorganic substances on the vessel walls on the gas-phase oxidation of methanol catalysed by nitric oxide. The results show that, whereas packing the vessel does not have a marked effect on the rate, the kinetics of the reaction are profoundly influenced by the nature of the surface. The results suggest that the methanol-oxidation chains are initiated at the surface by reaction between methanol and nitrogen dioxide, and that HO2 radicals play an important role in the subsequent chain reaction.

Kinetics of Pd/alumina catalysed 1,2-dichloroethane gas-phase oxidation

2006 ◽  
Vol 61 (11) ◽  
pp. 3564-3576 ◽  
Author(s):  
A. Aranzabal ◽  
J.A. González-Marcos ◽  
J.L. Ayastuy ◽  
J.R. González-Velasco
Keyword(s):  
Gas Phase ◽  
Phase Oxidation ◽  
Gas Phase Oxidation ◽  
Kinetics Of

Kinetics of hydrolyses of o-methylbenzylideneaniline and o-hydroxybenzylideneaniline

1968 ◽  
Vol 46 (9) ◽  
pp. 1589-1592 ◽  
Author(s):  
Alfred V. Willi ◽  
José F. Siman
Keyword(s):  
Hydrogen Bond ◽  
Schiff Base ◽  
Rate Constants ◽  
Experimental Error ◽  
Steric Effect ◽  
Hydrolysis Rate ◽  
Aqueous Methanol ◽  
Buffer Solutions ◽  
Acid Catalyzed ◽  
Kinetics Of

Rates of hydrolysis have been measured for o-methylbenzylideneaniline, o-hydroxybenzylideneaniline, and benzylideneaniline in various buffer solutions in 20% (by volume) aqueous methanol at 29.9 °C. Rate constants for the o-CH3 compound and the unsubstituted Schiff base agree within experimental error which indicates that there is no appreciable rate retarding steric effect. The o-OH group decreases the hydrolysis rate at pH = 5.6 – 6.6 by approximately one power of ten. This effect is caused by the hydrogen bond between the OH group and the azomethine N, which renders the Schiff base less accessible to acid-catalyzed hydrolysis.

Kinetics of the gas-phase oxidation of methanol catalysed by hydrogen bromide

1964 ◽  
Vol 17 (5) ◽  
pp. 551
Author(s):  
JJ Batten
Keyword(s):  
Nitric Oxide ◽  
Gas Phase ◽  
Maximum Rate ◽  
Hydrogen Bromide ◽  
Oxidation Of Methanol ◽  
Catalysed Reaction ◽  
Phase Oxidation ◽  
Gas Phase Oxidation ◽  
Kinetics Of ◽  
Uncatalysed Reaction

The homogeneous, gas-phase oxidation of methanol, catalysed by small amounts of hydrogen bromide, has been studied in a boric acid coated vessel at 310�. Under these conditions no reaction takes place in the absence of hydrogen bromide. The kinetics of the reaction and the rate of accumulation of formaldehyde in the products are compared with previously published data on the nitric oxide catalysed reaction at 310� and the uncatalysed reaction at 390�, i.e. at comparable rates of oxidation. The kinetics of the reaction were studied by means of pressure-time curves, and these were found to be of a similar shape to those of the uncatalysed reaction at 390�, and the nitric oxide catalysed reaction at 310�. The maximum rate was increased by the addition of "inert" gas. This rate varied as the methanol and hydrogen bromide pressures raised to the powers 0.7 and 1.3 respectively. On the other hand, increase in the oxygen pressure inhibited the maximum rate. The overall activation energy was 27 kcal mole-1. These kinetic data are similar to those of the nitric oxide catalysed reaction but differ markedly from those of the uncatalysed process at 390�. Under similar conditions, 15 mmHg hydrogen bromide were required to give a rate approximately equal to that obtained when using 2 mmHg nitric oxide. The maximum pressure of formaldehyde in the products was only about one-tenth of that obtained under similar conditions in the other two oxidations.

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