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Reactions methane, photochemical chlorination

Methane, chlorine, and recycled chloromethanes are fed to a tubular reactor at a reactor temperature of 490—530°C to yield all four chlorinated methane derivatives (14). Similarly, chlorination of ethane produces ethyl chloride and higher chlorinated ethanes. The process is employed commercially to produce l,l,l-trichloroethane. l,l,l-Trichloroethane is also produced via chlorination of 1,1-dichloroethane with l,l,2-trichloroethane as a coproduct (15). Hexachlorocyclopentadiene is formed by a complex series of chlorination, cyclization, and dechlorination reactions. First, substitutive chlorination of pentanes is carried out by either photochemical or thermal methods to give a product with 6—7 atoms of chlorine per mole of pentane. The polychloropentane product mixed with excess chlorine is then passed through a porous bed of Fuller s earth or silica at 350—500°C to give hexachlorocyclopentadiene. Cyclopentadiene is another possible feedstock for the production of hexachlorocyclopentadiene. [Pg.508]

Quantum yields for photochemically induced low-temperature reactions are also sensitive to intermolecular effects (i.e., the structure of the solid). For example, the quantum yield for reaction (9.15) in glassy mixtures of methane and chlorine at 20 K varies from 0.1 to 0.001, depending on the method of sample preparation [Benderskii et al., 1983]. The lowest values are obtained for samples prepared by thermal or ultrasonic annealing prior to UV photolysis. [Pg.324]

The sequence of a radical chain reaction is exemplified by the photochemical chlorination of methane (Box 2.1). [Pg.26]

Free-radical reactions may be divided into two classes. In the first, the product results from the combination of two radicals, as in the Kolbe synthesis. Electrolysis of the alkali metal salts of aliphatic carboxyhc acids results in the Hberation of alkyl radicals at the anode and their subsequent dimerization (Scheme 4.46). In the second class, the product results from the reaction of a radical with a molecule, as in the case of photochemical chlorination of methane. The fundamental difference between the two types of reaction is that the latter class involves a chain reaction. [Pg.129]

Let US work our way through a radical chain reaction. A good example is the photochemical chlorination of alkanes, shown below for methane ... [Pg.36]

Chlorine atoms obtained from the dissociation of chlorine molecules by thermal, photochemical, or chemically initiated processes react with a methane molecule to form hydrogen chloride and a methyl-free radical. The methyl radical reacts with an undissociated chlorine molecule to give methyl chloride and a new chlorine radical necessary to continue the reaction. Other more highly chlorinated products are formed in a similar manner. Chain terrnination may proceed by way of several of the examples cited in equations 6, 7, and 8. The initial radical-producing catalytic process is inhibited by oxygen to an extent that only a few ppm of oxygen can drastically decrease the reaction rate. In some commercial processes, small amounts of air are dehberately added to inhibit chlorination beyond the monochloro stage. [Pg.508]

All four chlorinated methanes are produced using methane chlorination or catalytic oxychlorination of methane. The methane chlorination is initiated thermally or photochemical ly. The strongly exothermic free-radical reaction is conducted without external heat at 400-450°C at slightly raised pressure [158],... [Pg.288]

The first step is the thermal or photochemical breaking of the chlorine-chlorine bond. This initiation reaction is followed by the first propagation step (Rg. 11.40), the abstraction of a hydrogen atom from methane by a chlorine atom to produce a methyl radical and hydrogen chloride. In the second propagation step, the methyl radical abstracts a chlorine atom from a chlorine molecule to give methyl chloride and another chlorine atom that can carry the chain reaction forward. There are many possible termination reactions Figure 11.40, which shows the overall mechanism, includes only one. [Pg.491]

Free-radical chain reactions also occur during the chlorination of methane (Chapter 10) and of the methyl group of methylbenzene. Ozone depletion by chlorofluorocarbons (CFCs), acid rain formation and formation of photochemical smog (Chapter 25 on the accompanying website) also involve free-radical reactions. (Free-radical reactions are also operating in unpolluted atmospheres and play an important role in all chemical reactions that occur in the gas phase.) The combustion of hydrocarbons, such as petrol, also proceeds via a free-radical mechanism, which has important consequences for the smooth running and performance of combustion engines. Chain reactions may also have ions as intermediates, as opposed to free radicals. [Pg.571]


See other pages where Reactions methane, photochemical chlorination is mentioned: [Pg.49]    [Pg.26]    [Pg.1358]    [Pg.177]    [Pg.27]    [Pg.219]    [Pg.372]    [Pg.304]    [Pg.964]    [Pg.201]    [Pg.117]    [Pg.622]    [Pg.293]    [Pg.502]    [Pg.168]    [Pg.219]   
See also in sourсe #XX -- [ Pg.129 ]




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Chlorinated methanes

Chlorination photochemical

Chlorination reactions

Chlorine reactions

Chlorins reactions

Methane chlorination

Methane reaction

Reactions methanation

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