Chlorine, reaction with alkanes compounds

Chirality center, 292 detection of, 292-293 Eischer projections and, 975-978 R,S configuration of, 297-300 Chitin, structure of, 1002 Chloral hydrate, structure of, 707 Chloramphenicol, structure of, 304 Chlorine, reaction with alkanes, 91-92,335-338 reaction with alkenes, 215-218 reaction with alkynes, 262-263 reaction with aromatic compounds, 550 Chloro group, directing effect of, 567-568... 

Chlorine or bromine reacts with alkanes in the presence of light (hv) or high temperatures to give alkyl halides. Usually, this method gives mixtures of halogenated compounds containing mono-, di-, tri- and tetra-halides. However, this reaction is an important reaction of alkanes as it is the only way to convert inert alkanes to reactive alkyl halides. The simplest example is the reaction of methane with CI2 to yield a mixture of chlorinated methane derivatives. 

In addition to combustion, alkanes undergo substitution reactions in which one or more H atoms on an alkane are replaced by atoms of another element. The most common such reaction is the replacement of H by chlorine, to yield organochlorine compounds. For example, methane reacts with chlorine to give chloromethane. This reaction begins with the dissociation of molecular chlorine, usually initiated by ultraviolet electromagnetic radiation ... 

The platinum-catalyzed reaction of alkanes with chlorine leads to alkyl chlorides and alcohols (Table 6, entry 46) with modest rates and conversions [50], Cydooctane can be easily dehydrogenated (Table 6, entry 47) in the presence of a stabilized vinylalkane by use of the neutral rhenium compound ReH7(PR3)2 [51]. By employing an iridium-based catalyst, the photochemical dehydrogenation of methylcydohexane to methylenecyclohexane is performed at room temperature... 

Most of the alkanes from petroleum are used to produce energy by combustion, but a few percent are converted to industrially useful compounds by controlled reaction with oxygen or chlorine. The alkanes are inert to attack by most chemical reagents and will react with oxygen and halogens only under the special conditions of radical initiated reactions. 

Hydrofluorocarbons have been proposed as CFC and HCFC substitutes since 1987, after the Montreal Protocol, with the aim of decreasing the ozone depletion. At present, these compounds are industrially produced by reaction of chlorinated hydrocarbons with HF. Environmental concerns have been raised regarding such processes, due to the co-production of huge amounts of HCl and the possible generation of dioxins and chlorinated compounds [1]. Due to their contribution to the greenhouse effect, fluorinated alkanes have often been replaced by other materials (e.g., natural refrigerants) in several UE countries... 

Cyclic compounds undergo the same reactions as acyclic compounds. For example, cyclic alkanes, like acyclic alkanes, undergo radical substitution reactions with chlorine or bromine. 

Alkanes are called saturated hydrocarbons because they do not contain any double or triple bonds. Since they also have only strong cr bonds and atoms with no partial charges, alkanes are very umeactive. Alkanes do undergo radical substitution reactions with chlorine (Cl 2) or bromine (Br2) at high temperatures or in the presence of light, to form alkyl chlorides or alkyl bromides. The substitution reaction is a radical chain reaction with initiation, propagation, and termination steps. Unwanted radical reactions are prevented by radical inhibitors—compounds that destroy reactive radicals by creating umeactive radicals or compounds with only paired electrons. 

Direct halogenation of saturated hydrocarbons or alkanes (compounds with no double or triple bonds) works satisfactorily only with elemental chlorine and bromine. The reaction proceeds via the formation of halogen atoms [Eq. (62)], which are highly reactive free radicals (species containing an unpaired electron) ... 

A number of chlorinated hydrocarbons arise during reactions of alkanes and alkenes with various chlorinated compounds, or by degradation of other chlorinated compounds. For example, as components of acid protein hydrolysates by traditional technology (hydrolysis with hydrochloric acid), 1,2-dichloropropane and 1,3-dichloropropane (see Section 12.2.4.1) are produced, the precursors of which are residual triacylglycerols found in oilseed meals. 

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