The Low Frequency Fundamental Bands of Methyl Chloride, Methyl Bromide and Methyl Iodide

1935 ◽  
Vol 3 (7) ◽  
pp. 367-368 ◽  
Author(s):  
E. F. Barker ◽  
E. K. Plyler
Keyword(s):  
Methyl Iodide ◽  
Methyl Bromide ◽  
Low Frequency ◽  
Methyl Chloride ◽  
Chloride Methyl

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 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.

scholarly journals Strain IMB-1, a Novel Bacterium for the Removal of Methyl Bromide in Fumigated Agricultural Soils

1998 ◽  
Vol 64 (8) ◽  
pp. 2899-2905 ◽  
Author(s):  
Tracy L. Connell Hancock ◽  
Andria M. Costello ◽  
Mary E. Lidstrom ◽  
Ronald S. Oremland
Keyword(s):  
Methyl Iodide ◽  
Methyl Bromide ◽  
Agricultural Soils ◽  
Treatment Strategies ◽  
Methyl Chloride ◽  
Methylotrophic Bacterium ◽  
Rrna Gene ◽  
Low Concentrations ◽  
Novel Bacterium ◽  
Bacterium Strain

ABSTRACT A facultatively methylotrophic bacterium, strain IMB-1, that has been isolated from agricultural soil grows on methyl bromide (MeBr), methyl iodide, methyl chloride, and methylated amines, as well as on glucose, pyruvate, or acetate. Phylogenetic analysis of its 16S rRNA gene sequence indicates that strain IMB-1 classes in the alpha subgroup of the class Proteobacteria and is closely related to members of the genus Rhizobium. The ability of strain IMB-1 to oxidize MeBr to CO2 is constitutive in cells regardless of the growth substrate. Addition of cell suspensions of strain IMB-1 to soils greatly accelerates the oxidation of MeBr, as does pretreatment of soils with low concentrations of methyl iodide. These results suggest that soil treatment strategies can be devised whereby bacteria can effectively consume MeBr during field fumigations, which would diminish or eliminate the outward flux of MeBr to the atmosphere.

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 Femtosecond time-resolved photodissociation dynamics of methyl halide molecules on ultrathin gold films

2011 ◽  
Vol 2 ◽  
pp. 618-627 ◽  
Author(s):  
Mihai E Vaida ◽  
Robert Tchitnga ◽  
Thorsten M Bernhardt
Keyword(s):  
Methyl Iodide ◽  
Methyl Bromide ◽  
Uv Light ◽  
Strong Dependence ◽  
Methyl Chloride ◽  
Gold Surface ◽  
Rapid Quenching ◽  
Negative Ion ◽  
Time Resolved ◽  
Methyl Halide

The photodissociation of small organic molecules, namely methyl iodide, methyl bromide, and methyl chloride, adsorbed on a metal surface was investigated in real time by means of femtosecond-laser pump–probe mass spectrometry. A weakly interacting gold surface was employed as substrate because the intact adsorption of the methyl halide molecules was desired prior to photoexcitation. The gold surface was prepared as an ultrathin film on Mo(100). The molecular adsorption behavior was characterized by coverage dependent temperature programmed desorption spectroscopy. Submonolayer preparations were irradiated with UV light of 266 nm wavelength and the subsequently emerging methyl fragments were probed by photoionization and mass spectrometric detection. A strong dependence of the excitation mechanism and the light-induced dynamics on the type of molecule was observed. Possible photoexcitation mechanisms included direct photoexcitation to the dissociative A-band of the methyl halide molecules as well as the attachment of surface-emitted electrons with transient negative ion formation and subsequent molecular fragmentation. Both reaction pathways were energetically possible in the case of methyl iodide, yet, no methyl fragments were observed. As a likely explanation, the rapid quenching of the excited states prior to fragmentation is proposed. This quenching mechanism could be prevented by modification of the gold surface through pre-adsorption of iodine atoms. In contrast, the A-band of methyl bromide was not energetically directly accessible through 266 nm excitation. Nevertheless, the one-photon-induced dissociation was observed in the case of methyl bromide. This was interpreted as being due to a considerable energetic down-shift of the electronic A-band states of methyl bromide by about 1.5 eV through interaction with the gold substrate. Finally, for methyl chloride no photofragmentation could be detected at all.

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.

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