THE PHOTOCHEMICAL OXIDATION OF ALDEHYDES IN THE GASEOUS PHASE: PART III. THE ABSOLUTE VALUES OF THE VELOCITY CONSTANTS FOR THE PROPAGATING AND TERMINATING STEPS IN THE PHOTOCHEMICAL OXIDATION OF ACETALDEHYDE AND PROPIONALDEHYDE

1958 ◽  
Vol 36 (1) ◽  
pp. 268-278 ◽  
Author(s):  
C. A. McDowell ◽  
L. K. Sharples
Keyword(s):  
Gas Phase ◽  
Gaseous Phase ◽  
Mutual Interaction ◽  
Photochemical Oxidation ◽  
Velocity Constant ◽  
Kinetic Expression ◽  
The Absolute ◽  
Recombination Reactions

It has been established (Parts I and II) that the photochemical oxidation of acetaldehyde and propionaldehyde obeys the kinetic expression[Formula: see text]where RCHO represents the aldehyde and RCO3H the corresponding peracid. k3 is the velocity constant for the propagating reaction, and k6 that for the terminating reaction involving the mutual interaction of two RCO3 radicals. [Formula: see text] represents the rate of initiation of the photooxidation.Alcohols have been found to retard the photooxidation and it has been shown that the retarded reaction obeys the kinetic expression:[Formula: see text]It has thus been possible to determine the rates of initiation [Formula: see text] for each of the photooxidations. Application of the rotating sector technique has enabled the lifetime of the oxidation chains to be measured. These data together with the information given in Parts I and II have been used to calculate the absolute values for the velocity constants for the propagating and terminating reactions, k3 and k6:[Formula: see text]in the gas-phase photooxidations of acetaldehyde and propionaldehyde.The values of the respective velocity constants are: acetaldehyde at 20°, k3 = 8.05( ±2.04) × 103 1. mole−1 sec−1, k6 = 8.93( ±4.20) × 1010 1. mole−1 sec−1; propionaldehyde at 22°, k3 = 4.35( ±0.9) × 104 1. mole−1 sec−1, k6 = 2.69( ±1.35) × 1010 1 mole−1 sec−1.These values for the velocity constants for the "recombination" reactions of the peracetic and perpropionic radicals indicate that for these radicals reaction [6] is very efficient.

THE PHOTOCHEMICAL OXIDATION OF ALDEHYDES IN THE GASEOUS PHASE: PART I. THE KINETICS OF THE PHOTOCHEMICAL OXIDATION OF ACETALDEHYDE

1958 ◽  
Vol 36 (1) ◽  
pp. 251-257 ◽  
Author(s):  
C. A. McDowell ◽  
L. K. Sharples
Keyword(s):  
Gaseous Phase ◽  
Photochemical Oxidation ◽  
Velocity Constant ◽  
Kinetics Of

The photochemical oxidation of acetaldehyde has been studied in the gaseous phase at 20 °C. and a wavelength of 3130 Å. It has been established that when the pressure of oxygen is between 0.5 mm. and 150 mm. the reaction obeys the kinetic law:[Formula: see text]where k3 is the velocity constant for the propagating reaction [3]:[Formula: see text]and k6 is the velocity constant for the terminating reaction [6]:[Formula: see text][Formula: see text] is the rate of initiation of the photooxidation, i.e. the rate of formation of acetyl radicals, which are thought to be produced in one or both of the following ways:[Formula: see text]

THE PHOTOCHEMICAL OXIDATION OF ALDEHYDES IN THE GASEOUS PHASE: PART II. THE KINETICS OF THE PHOTOCHEMICAL OXIDATION OF PROPIONALDEHYDE

1958 ◽  
Vol 36 (1) ◽  
pp. 258-267 ◽  
Author(s):  
C. A. McDowell ◽  
L. K. Sharples
Keyword(s):  
Free Radicals ◽  
Excited States ◽  
Gaseous Phase ◽  
Photochemical Oxidation ◽  
Radical Process ◽  
Velocity Constant ◽  
Absorption Of Light ◽  
Oxidation Chain ◽  
Kinetics Of ◽  
Free Radical Process

The photochemical oxidation of propionaldehyde has been studied in the gaseous phase at 23 °C. and a wavelength of 3130 Å. With pressures of oxygen varying from 0.3 mm. to 100 mm. Hg it has been established that the reaction obeys the same kinetic law as that found for the corresponding reaction with acetaldehyde, namely:[Formula: see text]where k3 is the velocity constant for the propagating reaction [3]:[Formula: see text]and k6 is the velocity constant for the terminating reaction [6]:[Formula: see text][Formula: see text]is the rate of initiation and it is regarded as being a composite quantity representing the rate of formation of propionyl radicals, which are thought to be the initiators of the oxidation chain. The propionyl radicals are thought to be formed by two processes: (a) from the subsequent reactions of free radicals produced in the primary free radical process which occurs when propionaldehyde absorbs a quantum of radiation at 3130 Å, and (b) from the subsequent reactions, with oxygen, of excited states of propionaldehyde, which are also thought to be formed by the absorption of light of wavelength 3130 Å.

Analysis of chlorinated hydrocarbons in gas phase using a portable membrane inlet mass spectrometer

2016 ◽  
Vol 8 (36) ◽  
pp. 6607-6615 ◽  
Author(s):  
Stamatios Giannoukos ◽  
Boris Brkić ◽  
Stephen Taylor
Keyword(s):  
Gas Phase ◽  
Mass Spectrometer ◽  
Gaseous Phase ◽  
Chlorinated Hydrocarbons ◽  
Volatile Chlorinated Hydrocarbons ◽  
First Time

A compact portable membrane inlet mass spectrometer (MIMS) has been used for the first time to detect and monitor, both qualitatively and quantitatively, volatile chlorinated hydrocarbons in the gaseous phase.

Pollution Level and Distribution of PCDD/PCDF Congeners between Gas Phase and Particulate Phase in early Spring Air of Dalian, China

2011 ◽  
Vol 71-78 ◽  
pp. 2679-2682
Author(s):  
Xiu Hua Zhu ◽  
Song Tao Qin ◽  
Qian Xu ◽  
Yu Wen Ni ◽  
Ji Ping Chen ◽  
...  
Keyword(s):  
Gas Phase ◽  
Gaseous Phase ◽  
High Volume ◽  
Ambient Air ◽  
Early Spring ◽  
Pollution Level ◽  
Particulate Phase ◽  
Spring Season ◽  
International Standard

Ambient air of Dalian was sampled with active high-volume air samplers in early spring time. The concentrations and the congeners between gas phase and particulate phase of polychlorinated dibenzo-p-dioxins and dibenzofurans(PCDD/Fs) in the air were measured. Samples analysis results showed that the concentration of PCDD/Fs in particulate phase was higher than that in gas phase. The ratio of PCDD to PCDF in gaseous phase and particulate phase was lower than 0.4. The main sources of atmospheric PCDD/Fs in Dalian early spring season were coal-related source. The total I-TEQ in gaseous phase and particulate phase was 30.3 and 143.6 fg m-3, respectively. The I-TEQ of Dalian early spring atmosphere was lower than international standard, the atmospheric quality in Dalian was better.

Improved synthesis and crystal structure of the parent 1,3,5-trisilacyclohexane

2016 ◽  
Vol 71 (1) ◽  
pp. 77-79 ◽  
Author(s):  
Eugen Weisheim ◽  
Hans-Georg Stammler ◽  
Norbert W. Mitzel
Keyword(s):  
Crystal Structure ◽  
Solid State ◽  
Electron Diffraction ◽  
Gas Phase ◽  
Gaseous Phase ◽  
Chair Conformation ◽  
Gas Electron Diffraction ◽  
State Structure ◽  
Synthesis And Crystal Structure ◽  
Bond Lengths

AbstractThe crystal structure and an improved synthesis of 1,3,5-trisilacyclohexane are reported. The solid state structure is compared with the reported structure determined in the gas phase by gas electron diffraction (GED). 1,3,5-Trisilacyclohexane adopts a chair conformation in the solid state. The Si–C bond lengths as well as all angles of 1,3,5-trisilacyclohexane in the solid state have similar dimensions compared to the structure in the gaseous phase.

The reactions of O(3P) with 2-propanone, 2-butanone, and 3-pentanone

1986 ◽  
Vol 64 (7) ◽  
pp. 1408-1414 ◽  
Author(s):  
John M. Roscoe
Keyword(s):  
Gas Phase ◽  
Rate Constants ◽  
Substrate Concentration ◽  
Activation Energies ◽  
Absolute Rate ◽  
The Absolute

The reactions of O(3P) with 2-propanone, 2-butanone, and 3-pentanone have been studied kinetically as a function of temperature and substrate concentration. The absolute rate constants for these reactions in the gas phase, in the units M−1 s−1, obey the following relations.[Formula: see text]The activation energies for these reactions are comparable to those for the reactions of O(3P) with alcohols, but the preexponential factors for the reactions of O(3P) with these ketones are significantly smaller than those for the analogous reactions with alcohols. The available data indicate that the reactivity of O(3P) toward ketones shows a variation with polar effects of substituents which is similar to that found for the reactions of OH with ketones.

scholarly journals Photochemical Degradation of Cyanides and Thiocyanates from an Industrial Wastewater

Molecules ◽  
2019 ◽  
Vol 24 (7) ◽  
pp. 1373 ◽  
Author(s):  
Juan Jose Viña Mediavilla ◽  
Begoña Fernandez Perez ◽  
Maria C. Fernandez de Cordoba ◽  
Julia Ayala Espina ◽  
Conchi O. Ania
Keyword(s):  
Uv Light ◽  
Degradation Mechanism ◽  
Industrial Effluents ◽  
Photochemical Oxidation ◽  
Solar Light ◽  
Photochemical Degradation ◽  
Simulated Solar Light ◽  
Cyanide Detoxification ◽  
Detoxification Systems ◽  
Recombination Reactions

We have explored the simultaneous degradation of cyanides and thiocyanate present in wastewaters from a cokemaking factory using photoassisted methods under varied illumination conditions (from simulated solar light to UV light). Overall, the photochemical degradation of cyanides was more efficient than that of thiocyanates, regardless of the illumination conditions, the effect being more pronounced in the absence of a photocatalyst. This is due to their different degradation mechanism that in the case of thiocyanates is dominated by fast recombination reactions and/or charge transfer reactions to electron scavengers. In all cases, cyanate, ammonia, nitrates, and nitrites were formed at different amounts depending on the illumination conditions. The conversion yield under simulated solar light was almost complete for cyanides and quite high for thiocyanates after 6 h of illumination. Regarding toxicity, photochemical oxidation at 254 nm and under simulated solar light decreased significantly the toxicity of the pristine wastewater, showing a correlation with the intensity of the irradiation source. This indicate that simulated light can be effectively used to reduce the toxicity of industrial effluents, opening an interesting perspective for optimizing cyanide detoxification systems based on natural light.

Photochemical oxidation of atmospheric sulphur dioxide

1979 ◽  
Vol 290 (1376) ◽  
pp. 543-550 ◽  
Keyword(s):  
Free Radicals ◽  
Gas Phase ◽  
Sulphur Dioxide ◽  
Heterogeneous Reactions ◽  
Photochemical Oxidation ◽  
Gas Phase Reactions ◽  
Oxidation Rates ◽  
Polluted Atmosphere ◽  
Gas Phase Oxidation ◽  
Background Troposphere

Oxidation of atmospheric sulphur dioxide can occur by homogeneous photochemically initiated gas-phase reactions as well as by heterogeneous reactions in cloud and fog droplets. Gas phase oxidation can result from reactions of excited SO 2 molecules formed by absorption of solar u.v. radiation by ground state SO 2 , from reactions of SO 2 with photochemically generated OH and RO 2 free radicals, and from its reaction with transient species produced in thermal ozone—alkene reactions. Evaluation of the available mechanistic and rate data reveals that, of these three processes, oxidation by free radicals, particularly OH, is likely to be the most important in the atmosphere. Oxidation rates of up to 4 % h -1 are predicted for a hydrocarbon-NO x polluted atmosphere under western European summertime conditions. This can lead to the formation of elevated concentrations of sulphuric acid and sulphate aerosol in polluted air. In the natural background troposphere oxidation rates are much less, ca . 0.3 % h -1 averaged over 24 h, but probably still significant as a source of atmospheric sulphates.

Sign in / Sign up

Export Citation Format

Share Document