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Two free radicals (chlorine and chlorine, chlorine and methyl, or methyl and methyl) combine: Methane chlorination: termination The last possibility generates in an impurity in the final mixture (notably, an organic molecule with a longer carbon chain than the reactants). The net reaction is: Methane chlorination overall reaction
Reaction scheme of the photochlorination of the methyl group of toluene. Photochlorination is a chlorination reaction that is initiated by light. Usually a C-H bond is converted to a C-Cl bond. Photochlorination is carried out on an industrial scale.
For example, in the chlorination of methane, there is a two-step propagation cycle involving as chain carriers a chlorine atom and a methyl radical [1] which are regenerated alternately: ·Cl + CH 4 → HCl + ·CH 3 ·CH 3 + Cl 2 → CH 3 Cl + ·Cl. The two steps add to give the equation for the overall chain reaction: CH 4 + Cl 2 → CH 3 Cl + HCl
Methane chlorination is a chain reaction. If only the products and reactants are analyzed, the result is: CH 4 + 4 Cl 2 → CCl 4 + 4 HCl. However, this reaction has 3 intermediate reactants which are formed during a sequence of 4 irreversible second order reactions until we arrive at the final product. This is why it is called a chain reaction.
A smaller amount of chloromethane is produced by treating a mixture of methane with chlorine at elevated temperatures. This method, however, also produces more highly chlorinated compounds such as dichloromethane, chloroform, and carbon tetrachloride. For this reason, methane chlorination is usually only practiced when these other products are ...
However, the extent of chlorination is difficult to control. Aryl chlorides may be prepared by the Friedel-Crafts halogenation, using chlorine and a Lewis acid catalyst. [2] The haloform reaction, using chlorine and sodium hydroxide, is also able to generate alkyl halides from methyl ketones, and related compounds. Chloroform was formerly ...
The reaction typically involves free radical pathways. The regiochemistry of the halogenation of alkanes is largely determined by the relative weakness of the C–H bonds. This trend is reflected by the faster reaction at tertiary and secondary positions. Free radical chlorination is used for the industrial production of some solvents: [2]
DCM is produced by treating either chloromethane or methane with chlorine gas at 400–500 °C. At these temperatures, both methane and chloromethane undergo a series of reactions producing progressively more chlorinated products. In this way, an estimated 400,000 tons were produced in the US, Europe, and Japan in 1993. [12] CH 4 + Cl 2 → CH ...