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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.
In searching for a new refrigerant, requirements for the compound were: low boiling point, low toxicity, and to be generally non-reactive.
In a demonstration for the American Chemical Society, Midgley flamboyantly demonstrated all these properties by inhaling a breath of the gas and using it to blow out a candle During World War II, various chloroalkanes were in standard use in military aircraft, although these early halons suffered from excessive toxicity.
Billions of kilograms of chlorodifluoromethane are produced annually as precursor to tetrafluoroethylene, the monomer that is converted into Teflon.
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.
The most common representative is dichlorodifluoromethane (R-12 or Freon-12).
A traditional European atmosphere plus attention to detail offers a comfortable yet refined respite.The decreased volatility is attributed to the molecular polarity induced by the halides, which induces intermolecular interactions.Thus, methane boils at −161 °C whereas the fluoromethanes boil between −51.7 (CF).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.