Kinetic Study of the Photochlorination of 2,3-Dimethylbutane 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 ?-Complex. Identification of ...

Article abstract of DOI:10.1021/ja00305a023

Five photochemical source have been employed to generate chlorine atoms in solution in the presence of benzene at room temperature.The chlorine atoms react with benzene (k3=6.0*10⁹ M^-1 s^-1 to form a species which is firmly identified as the C6H6Cl. ?-complex. 1.Laser flash photolytic techniques have been employed to measure absolute rate constants for hydrogen atom abstraction from various alkanes by 1.This species proved to have a reactivity less than that of "free" chlorine atom but greater than that of the tert-butoxyl radical.These absolute rate constants are in satisfactory agreement with the results of competitive chlorinations of certain alkanes in benzene solvent.Absolute rate constants were also measured for the reaction of the "free" chlorine atom with 2,3-dimethylbutane (DMB).A reasonably comprehensive study of the tertiary/primary selectivity for chlorination of DMB over a range of concentrations and in a variety of benzene/CCl4 mixtures has been carried out.It is shown that this DMB selectivity data can be quantitatively described by a kinetic scheme which involves hydrogen abstraction by only two species, "free" Cl. atoms and 1.