THE PHOTOLYSIS OF MIXTURES OF ACETONE AND SOME HALOGENATED HYDROCARBONS

1955 ◽  
Vol 33 (2) ◽  
pp. 396-399 ◽  
Author(s):  
M. J. Ridge ◽  
E. W. R. Steacie
Keyword(s):  
Activation Energy ◽  
Methyl Bromide ◽  
Methylene Chloride ◽  
Hydrogen Abstraction ◽  
Methyl Chloride ◽  
Halogenated Hydrocarbons ◽  
Methyl Radicals ◽  
Hydrocarbon Mixtures ◽  
Chloride Methyl

The composition of the products of photolysis of acetone in the presence of methyl chloride, methyl bromide, methylene chloride, and methylene bromide has been determined. These reactions are attended by complications not found with the photolysis of acetone–hydrocarbon mixtures. Failure to take into account reactions resulting from the formation of halogen hydrides and to allow for the presence of ethylene invalidates the values obtained by Raal and Steacie for the activation energy for hydrogen abstraction by methyl radicals from some halogenated hydrocarbons.

scholarly journals Halogenated organic species over the tropical South American rainforest

2008 ◽  
Vol 8 (12) ◽  
pp. 3185-3197 ◽  
Author(s):  
S. Gebhardt ◽  
A. Colomb ◽  
R. Hofmann ◽  
J. Williams ◽  
J. Lelieveld
Keyword(s):  
Boundary Layer ◽  
Methyl Bromide ◽  
Methyl Chloride ◽  
Minor Importance ◽  
Global Budget ◽  
Airborne Measurements ◽  
Tropical Vegetation ◽  
Net Flux ◽  
Net Fluxes ◽  
Chloride Methyl

Abstract. Airborne measurements of the halogenated trace gases methyl chloride, methyl bromide and chloroform were conducted over the Atlantic Ocean and about 1000 km of pristine tropical rainforest in Suriname and French Guyana (3–6° N, 51–59° W) in October 2005. In the boundary layer (0–1.4 km), maritime air masses, advected over the forest by southeasterly trade winds, were measured at various distances from the coast. Since the organohalogens presented here have relatively long atmospheric lifetimes (0.4–1.0 years) in comparison to the advection times from the coast (1–2 days), emissions will accumulate in air traversing the rainforest. The distributions of methyl chloride, methyl bromide and chloroform were analyzed as a function of time the air spent over land and the respective relationship used to determine net fluxes from the rainforest for one week within the long dry season. Net fluxes from the rainforest ecosystem have been calculated for methyl chloride and chloroform as 9.5 (±3.8 2σ) and 0.35 (±0.15 2σ)μg m-2 h−1, respectively. No significant flux was observed for methyl bromide within the limits of these measurements. The global budget of methyl chloride contains large uncertainties, in particular with regard to a possible source from tropical vegetation. Our measurements are used in a large-scale approach to determine the net flux from a tropical ecosystem to the planetary boundary layer. The obtained global net flux of 1.5 (±0.6 2σ) Tg yr-1 for methyl chloride is at the lower end of current estimates for tropical vegetation sources, which helps to constrain the range of tropical sources and sinks (0.82 to 8.2 Tg yr-1 from tropical plants, 0.03 to 2.5 Tg yr-1 from senescent/dead leaves and a sink of 0.1 to 1.6 Tg yr-1 by soil uptake). Nevertheless, these results show that the contribution of the rainforest ecosystem is the major source in the global budget of methyl chloride. For chloroform, the extrapolated global net flux from tropical ecosystems is 56 (±23 2σ) Gg yr−1, which is of minor importance compared to the total global sources and might be already contained in the soil emission term.

The kinetics of hydrolysis

1953 ◽  
Vol 220 (1142) ◽  
pp. 386-396 ◽  
Keyword(s):  
Methyl Bromide ◽  
Heat Content ◽  
Methyl Chloride ◽  
Vapour Phase ◽  
Energy Of Activation ◽  
Complicated Course ◽  
Complex Temperature ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Chloride Methyl

The rates of hydrolysis of methyl chloride, methyl bromide and methyl iodide have been measured in the absence of the vapour phase at 10° intervals between 30 and 90°C. In this region, the energy of activation at first decreases with a rise in temperature, and then passes through a minimum value. Taking the energy of crystalline methyl bromide at the absolute zero of temperature as being itself zero, the partial heat content of the critically activated solute has been evaluated, and found to be constant. The complicated course followed by the energy of activation appears to be due to the complex temperature variation of the average heat content of the normal solute, which, in the region examined, rises as the temperature is raised, and passes through a maximum value.

scholarly journals The kinetics of certain reactions between methyl halides and anions in water

1949 ◽  
Vol 196 (1047) ◽  
pp. 540-553 ◽  
Keyword(s):  
Dipole Moment ◽  
Methyl Iodide ◽  
Methyl Bromide ◽  
Methyl Chloride ◽  
Polar Molecules ◽  
Methyl Halides ◽  
Methyl Halide ◽  
Kinetics Of ◽  
Chloride Methyl

The rates at which methyl chloride, methyl bromide and methyl iodide react with the hydroxyl and the thiosulphate ions in water have been measured at various concentrations and temperatures. The apparent energies of activation in both series increase in the same direction as the dipole moment of the methyl halide. The results are discussed in terms of a theory of the kinetics of the reactions between ions and polar molecules in solution.

scholarly journals Halogenated organic species over the tropical rainforest

2008 ◽  
Vol 8 (1) ◽  
pp. 1159-1190 ◽  
Author(s):  
S. Gebhardt ◽  
A. Colomb ◽  
R. Hofmann ◽  
J. Williams ◽  
J. Lelieveld
Keyword(s):  
Methyl Bromide ◽  
Tropical Rainforest ◽  
Methyl Chloride ◽  
Trade Winds ◽  
Airborne Measurements ◽  
Model Studies ◽  
Emission Fluxes ◽  
Strong Source ◽  
Analytical System ◽  
Chloride Methyl

Abstract. Airborne measurements of the halogenated trace gases methyl chloride, methyl bromide and chloroform were conducted over the Atlantic Ocean and 1000 km of pristine tropical rainforest in Suriname and French Guyana (3–6° N, 51–59° W) in October 2005. In the boundary layer (0–1.4 km), maritime air masses initially low in forest hydrocarbons, advected over the forest by southeasterly trade winds, were measured at various distances from the coast. Since the organohalogens presented here have relatively long atmospheric lifetimes (0.4–1.0 years) in comparison to the transport times (1–2 days), emissions will accumulate in air traversing the rainforest. The distributions of methyl chloride, methyl bromide and chloroform were analyzed as a function of forest contact time and the respective relationship used to determine fluxes from the rainforest during the long dry season. Emission fluxes have been calculated for methyl chloride and chloroform as 9.4 (±4.0 2σ) and 0.34 (0.14± 2σ) μg m−2 h−1, respectively. No significant flux from the rainforest was observed for methyl bromide within the limits of these measurements. The flux of methyl chloride was in general agreement with the flux measured over the same region in March 1998 during the LBA Claire project using a different analytical system. This confirms that the rainforest is a strong source for methyl chloride and suggests that this emission is relatively uniform throughout the year. In contrast the chloroform flux derived here is a factor of three less than previous measurements made in March 1998 suggesting a pronounced ecosystem variation. The differences in chloroform fluxes could not be attributed to either temperature or rainfall changes. The global extrapolation of the derived fluxes led to 1.5 (±0.6 2σ) Tg yr−1 for methyl chloride, which is in the range of the missing source postulated by previous model studies and 55 (±22 2σ) Gg yr−1 for chloroform.

Isotopic Characterization (2H, 13C, 37Cl, 81Br) of the Abiotic Sinks of Methyl Bromide and Methyl Chloride in Water and Implications for Future Studies.

2018 ◽  
Author(s):  
Axel Horst ◽  
Magali Bonifacie ◽  
Gérard Bardoux ◽  
Hans-Hermann Richnow
Keyword(s):  
Methyl Bromide ◽  
Isotope Fractionation ◽  
Methyl Chloride ◽  
Methyl Halides ◽  
Future Studies ◽  
Halide Exchange ◽  
Isotopic Characterization

In this study we investigated the isotope fractionation of the abiotic sink (hydrolysis, halide exchange) of methyl halides in water.<br>

Hydrogen abstraction by methyl radicals in glasses

1984 ◽  
Vol 78 ◽  
pp. 175 ◽  
Author(s):  
Takahisa Doba ◽  
Keith U. Ingold ◽  
Willem Siebrand ◽  
Timothy A. Wildman
Keyword(s):  
Hydrogen Abstraction ◽  
Methyl Radicals
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