Free-radical halogenation distribution". For propane and higher alkanes, the hydrogen atoms which form part of CH (or CH) groups are preferentially replaced. The reactivity of the different halogens varies considerably. The relative rates are: fluorine (108) > chlorine (1) > bromine (7 × 10) > iodine (2 × 10). Hence, the reaction of alkanes with fluorine is difficult to control, that with chlorine is moderate to fast, that with bromine is slow and requires high levels of UV irradiation while the reaction with iodine is practically nonexistent and thermodynamically unfavorable. A common method in organic synthesis employing is the Wohl–Ziegler reaction, which
Chlorine nuclide in a ratio of about (7–10) × 10 to 1 with stable chlorine isotopes: it is produced in the atmosphere by spallation of Ar by interactions with cosmic ray protons. In the top meter of the lithosphere, Cl is generated primarily by thermal neutron activation of Cl and spallation of K and Ca. In the subsurface environment, muon capture by Ca becomes more important as a way to generate Cl. Chlorine is intermediate in reactivity between fluorine and bromine, and is one of the most reactive elements. Chlorine is a weaker oxidising agent than fluorine but a stronger one