Photochlorination alkanes

Bunce, N. J., K. U. Ingold, J. P. Landers, J. Lusztyk, and J. C. Scaiano, Kinetic Study of the Photochlorination of 2,3-Dimethyl-butane and Other Alkanes in Solution in the Presence of Benzene. First Measurements of the Absolute Rate Constants for Hydrogen Abstraction by the Free Chlorine Atom and the Chlorine Atom-Benzene tr -Complex. Identification of These Two Species as the Only Hydrogen Abstractors in These Systems, . /. Am. Chem. Soc., 107, 5464-5472 (1985). 

A uniquely high degree of terminal (methyl) selectivities in photochlorination of n-alkanes adsorbed on pentasil zeolites was reported.125 Monochlorination at the terminal methyl group was found to be a function of conversion, water content, Si/Al ratio of the zeolite, and loading of the alkane. 

Chlorination of Alkanes. The most direct and economical method for the manufacture of chloromethanes is the thermal free-radical chlorination of methane.176 177 Whereas in the 1940s and 1950s photochlorination was practiced in some plants, thermal chlorination is the principal industrial process today. The product chloromethanes are important solvents and intermediates. Commercial operations perform thermal chlorination at about 400-450°C. Vapor-phase photochemical chlorination of methane may be accomplished at 50-60°C. Fast and effective removal of heat associated with thermally induced free-radical substitution is a crucial point. Inadequate heat control may lead to explosion attributed to the uncontrollable pyrolysis liberating free carbon and much heat ... 

Photochlorination of n-alkanes in solution results in substitution at both primary and secondary carbon atoms [213], When n-alkanes included in the channels of zeolite LZ-105 (structure very much like ZSM-5 with channel diameter 5.5 A) were photochlorinated, selective substitution at the primary carbon atom occurred also multiple chlorination was avoided. The high selectivity can be attributed to the template effect of the zeolite. Zeolite LZ-105 includes n-alkanes into its channels and holds them in such a way that only the primary (terminal) carbons are exposed to the attacking chlorine atom (Figure 34). It is the tight fit of the alkanes in the channels that forbids both access of chlorine atoms to secondary carbon atoms and folding of the alkane chain, which would permit secondary carbons to be exposed to the reagent. 

K. U. Ingold, J. Lusztyk, K. D. Raner, The unusual and the unexpected in an old reaction. The photochlorination of alkanes with molecular chlorine in solution, Acc. Chem. Res 1990, 23,... 

Photochlorination has been recommended for the preparation of choice of cyclodecene from cyclodecane via the intermediate chloride.Bromine is a rather weak brominating agent for alkanes and only unusually favorable substrates, like adamantane, react at a reasonable rate. The mixture HgO/Br2 is much more reactive than bromine itself, as shown by the facile bromination of 1,1,3,3-tetramethylbutane. Silver hexafluoroantimonate has also been used to activate bromine for this type of reaction. Iodine is normally ineffective in functionalizing alkanes, but use of y-irradiation of a solution of I2 in alkanes leads to unselective formation of all possible iodoalkanes. ... 

Photochlorination and photobromination of bicyclo[n.l.O]alkanes gave complex product mixtures containing 1,3-dihalides from substitution reactions, as well as products derived from abstraction of the a-hydrogens. 

The Photochlorination of Alkanes with Molecular Chlorine in Solution, Acc. Chem. Res. 1990, 23, 219 225. 

Turro NJ, Eehlner JR, Hessler DP et al (1988) Photochlorination of n-alkanes adsorbed on pentasil zeolites. J Org Chem 53(16) 3731-3735... 

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