Abstraction of halogen atoms by methyl radicals. Part 1.—Exchange reactions involving methyl iodide and methyl bromide

1961 ◽  
Vol 57 (0) ◽  
pp. 1905-1914 ◽  
Author(s):  
F. W. Evans ◽  
M. Szwarc
Keyword(s):  
Methyl Iodide ◽  
Methyl Bromide ◽  
Methyl Radicals ◽  
Exchange Reactions ◽  
Halogen Atoms

High Temperature Absorption of the 3.39 µm He-Ne Laser Line by Small Hydrocarbons

1978 ◽  
Vol 32 (5) ◽  
pp. 489-493 ◽  
Author(s):  
D. B. Olson ◽  
W. G. Mallard ◽  
W. C. Gardiner
Keyword(s):  
High Temperature ◽  
Temperature Dependence ◽  
Methyl Iodide ◽  
Transient Absorption ◽  
Broad Band ◽  
Laser Line ◽  
Methyl Radicals ◽  
Large Numbers ◽  
Absorbing States ◽  
No Absorption

Absorptivity measurements for the 3.39 µm He-Ne laser line are reported for methane, acetylene, ethylene, ethane, propane, n-butane, and n-pentane over the temperature range 300 < T < 2000°K. Shock-heated mixtures containing formaldehyde and methyl iodide showed no absorption or transient absorption at any temperature that could be attributed to formaldehyde or methyl radicals. The temperature dependence of the absorptivities of the C2 and higher hydrocarbons was much weaker than for methane. Comparison with simple theoretical expectations and broad-band absorptivities showed that the higher hydrocarbon absorptions include quite large numbers of absorbing states.

Estimation of State of Cure with S-35

1960 ◽  
Vol 33 (1) ◽  
pp. 181-198
Author(s):  
H. L. Pederson
Keyword(s):  
Methyl Iodide ◽  
Benzene Solution ◽  
Active Material ◽  
Zinc Salt ◽  
Minor Importance ◽  
Exchange Reactions ◽  
Extensive Discussion ◽  
General Picture ◽  
Sulfur Bond

Abstract The use of S-35 in a vulcanizate can lead to an easy determination of bound sulfur as the ratio of activities of the acetone extracted sample and the same sample in its original state. At present, we do not specify the meaning of the sulfur value determined in this manner otherwise than that it is a gross value ideally free from accelerator sulfur. A number of Russian papers have reported the use of radiosulfur in vulcanization studies—for instance, Blokh's survey. Later Dogadkin described exchange reactions specifying the character of the sulfur bond in combination with an extensive discussion of the chain mechanism for the function especially of thiurams, leading to at least three types of vulcanizates: nonsulfur thiuram cures with —C—C— crosslinks and no exchange at all, DPG stocks having a high exchange rate, and thiazole mixes having intermediate rates. Of course, this is a very general picture explaining only the outstanding differences in aging stabilities imported in the systems mentioned. The quoted papers give very little experimental detail. However, there is a description of the exchange that can be performed by boiling the sample in a benzene solution of the reactant—e.g., sulfur or accelerator. It is of minor importance where the radioactivity is placed; however, the treatment of inactive vulcanizates with solutions of active material is very unpleasant. Therefore the active material is added in every case by compounding and the exchange is carried out by means of an inactive solution in acetone. The present work was undertaken to investigate differences in stability of the sulfur bond in vulcanizates having increasing states of cure, preferentially in a series of vulcanizations at constant temperature. In addition to exchange with elemental sulfur and sulfur donors (tetramethylthiuramdisulfide) we have investigated the Meyer and Hohemenser reaction with methyl iodide, more elaborately developed by the brilliant work of Selker and Kemp. This reaction is thought specifically to indicate the allylic bound sulfur. It is easily performed by boiling the active vulcanizate with a mixture of methyl iodide and acetone. Fletcher and Fogg indicate in their recent work that thiuram-sulfur systems owe their remarkable aging resistance to the content of ZnDC formed by the decomposition of thiuram during cure. Further, it is well known that certain compounds, such as the zinc salt of MBT, give a similar improvement. We therefore stress that stabilities as stated here, based upon the exchange reaction, will not necessarily bear a unique relation to aging stability, but rather show an intrinsic stability of the sulfur bond.

Moderation of Hot Methyl Radicals in Photolysis of Methyl Iodide

1953 ◽  
Vol 21 (10) ◽  
pp. 1894-1894 ◽  
Author(s):  
Frank P. Hudson ◽  
Russell R. Williams ◽  
William H. Hamill
Keyword(s):  
Methyl Iodide ◽  
Methyl Radicals

Methyl bromide, other brominated methanes, and methyl iodide in polar firn air

2001 ◽  
Vol 106 (D2) ◽  
pp. 1595-1606 ◽  
Author(s):  
W. T. Sturges ◽  
H. P. McIntyre ◽  
S. A. Penkett ◽  
J. Chappellaz ◽  
J.-M. Barnola ◽  
...  
Keyword(s):  
Methyl Iodide ◽  
Methyl Bromide

Highly photostable luminescent open-shell (3,5-dihalo-4-pyridyl)bis(2,4,6-trichlorophenyl)methyl radicals: significant effects of halogen atoms on their photophysical and photochemical properties

RSC Advances ◽  
2015 ◽  
Vol 5 (79) ◽  
pp. 64802-64805 ◽  
Author(s):  
Yohei Hattori ◽  
Tetsuro Kusamoto ◽  
Hiroshi Nishihara
Keyword(s):  
Quantum Yield ◽  
Open Shell ◽  
Methyl Radicals ◽  
Halogen Atoms ◽  
Photoluminescence Quantum Yield ◽  
Photochemical Properties

Highly photostable luminescent radicals, X2PyBTM (X = Br, Cl, F), were investigated. Br2PyBTM showed the highest photostability and F2PyBTM displayed the highest photoluminescence quantum yield of the three radicals.

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