Problems with carbon dating accuracy

Every permutation of fluorine, chlorine and hydrogen based on methane and ethane has been examined and most have been commercialized.

Furthermore, many examples are known for higher numbers of carbon as well as related compounds containing bromine.

A special numbering system is used for fluorinated alkanes, prefixed with Freon-, R-, CFC- and HCFC-, where the rightmost value indicates the number of fluorine atoms, the next value to the left is the number of hydrogen atoms plus 1, and the next value to the left is the number of carbon atoms less one (zeroes are not stated), and the remaining atoms are chlorine.

Freon-12, for example, indicates a methane derivative (only two numbers) containing two fluorine atoms (the second 2) and no hydrogen (1-1=0). Another, easier equation that can be applied to get the correct molecular formula of the CFC/R/Freon class compounds is this to take the numbering and add 90 to it.

The main advantage of this method of deducing the molecular composition in comparison with the method described in the paragraph above is that it gives the number of carbon atoms of the molecule.

Freons containing bromine are signified by four numbers.

Isomers, which are common for ethane and propane derivatives, are indicated by letters following the numbers : ) was used in fire extinguishers and glass "anti-fire grenades" from the late nineteenth century until around the end of World War II.

Because CFCs contribute to ozone depletion in the upper atmosphere, the manufacture of such compounds has been phased out under the Montreal Protocol, and they are being replaced with other products such as hydrofluorocarbons (HFCs) As in simpler alkanes, carbon in the CFCs bonds with tetrahedral symmetry.Because of their polarity, the CFCs are useful solvents, and their boiling points make them suitable as refrigerants.The CFCs are far less flammable than methane, in part because they contain fewer C-H bonds and in part because, in the case of the chlorides and bromides, the released halides quench the free radicals that sustain flames.They are also commonly known by the Du Pont brand name Freon.The most common representative is dichlorodifluoromethane (R-12 or Freon-12).

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