600-06-6Relevant articles and documents
Influence of Aromatic Solvents on the Selectivity for Photochlorination of 2,3-Dimethylbutane with Molecular Chlorine
Raner, K. D.,Lusztyk, J.,Ingold, K. U.
, p. 3652 - 3658 (2007/10/02)
The effect of benzene and a wide variety of substituted benzenes upon the photochlorination of 2,3-dimethylbutane (DMB) has been investigated under standard conditions (0.15 M DMB, 2.0 M arene in CCl4 at room temperature).The standard selectivities, Sstdm, are given by the product ratios / under these conditions.For arenes which are less electron rich than benzene, log Sstdm values decrease monotonically with the increase in the arenes' ionization potentials and with the decrease in the arenes' ?-basicities.For arenes which are moreelectron rich than benzene, Sstdm values are greater than for benzene only for the mono- and dialkylated benzenes and 1,3,5-tri-tert-butylbenzene.Chlorination in the presence of trimethylbenzenes, more highly methylated benzenes, and anisole afforded less selective mixtures of DMB chlorides than benzene.The reduced selectivities of the most electron-rich arenes is attributed to the low reactivities of their Cl./arene ?-complexes and the low yields of DMB chlorides, much of which are formed by hydrogen abstraction by the free Cl. atom.Ipso substitution occurs with bromo- and iodobenzene and these two arenes are more selective than would be predicted.It has also been demonstrated by laser flash photolysis that Cl./arene and Br./arene ?-complexes will appear to react with O2 only if the arene contains substituents which can donate hydrogen to the halogen atom and/or complex, viz., CH3, C(CH3)3, and OCH3 substituents for chlorine but only CH3 and OCH3 for bromine.This apparent reaction is due to interference by O2 in the process which otherwise would very rapidly "regenerate" the halogen atom/arene complex followingsuch hydrogen abstraction.
KINETIC ANALYSIS OF ALKANE POLYCHLORINATION WITH MOLECULAR CHLORINE. CHLORINE ATOM/MONOCHLORIDE GEMINATE PAIRS AND THE EFFECT OF REACTIVE 'CAGE WALLS' ON THE COMPETITION BETWEEN MONOCHLORIDE ROTATION AND CHLORINE ATOM ESCAPE.
Raner,Lusztyk,Ingold
, p. 3519 - 3524 (2007/10/02)
The free-radical chlorination of alkanes produces polychlorides even at low conversions. These are formed by reaction of chlorine atom/monochloride (or dichloride) geminate pairs. This process has been studied in detail in various solvent systems, and a kinetic scheme has been proposed. Deviations from this scheme have been rationalized as being due to competition between monochloride rotation and reaction of the chlorine atom with reactive molecules in the 'cage walls' surrounding the chlorine atom/chloride geminate pair. Analysis of the dichloride products supports the suggestion that monochloride rotation is not completely 'free' within the lifetime of the geminate pair.
REACTIONS OF BrCl WITH ALKYL RADICALS.
Skell, P. S.,Baxter, H. N.,Tanko, J. M.
, p. 5181 - 5184 (2007/10/02)
It is demonstrated that photohalogenation of low reactivity substrates with BrCl occurs mainly with Cl. selectivity.With tertiary or benzylic hydrogens in the substrate, mainly Br. selectivity is observed.These observations are rationalized, taking into account the relative concentrations of halogen atoms and their respective rates of hydrogen abstractions.The resultant radicals react with BrCl to make (RBr/RCl) in ratios between 1 and 15.
