Carbon dating process infornation
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An easy example is that of CFC-12, which gives: 90 12=102 -.
The value of this equation is always a three figure number. In part, these have been the result of natural factors, including the climatic changes of the Little Ice Age, and the Spörer and Maunder solar activity minima.In addition, however, changes in human activity since the middle of the 19th century have released C that occurred prior to 1955 mean that a single radiocarbon date may yield an imprecise calibrated age consisting of several possible age ranges.Ozone absorbs UV-B radiation, so its depletion allows more of this high energy radiation to reach the Earth's surface.Bromine atoms are even more efficient catalysts; hence brominated CFCs are also regulated.Illustrative is the synthesis of chlorodifluoromethane from chloroform: The brominated derivatives are generated by free-radical reactions of the chlorofluorocarbons, replacing C-H bonds with C-Br bonds.
The production of the anesthetic 2-bromo-2-chloro-1,1,1-trifluoroethane ("halothane") is illustrative: .
The physical properties of CFCs and HCFCs are tunable by changes in the number and identity of the halogen atoms.
In general they are volatile, but less so than their parent alkanes.
CFCs and HCFCs are used in a variety of applications because of their low toxicity, reactivity and flammability.
Every permutation of fluorine, chlorine and hydrogen based on methane and ethane has been examined and most have been commercialized.
Experimentation with chloroalkanes for fire suppression on military aircraft began at least as early as the 1920s. The Belgian scientist Frédéric Swarts pioneered the synthesis of CFCs in the 1890s.