Photolysis of carbon tetrachloride in the presence of alkanes

Abstract

The photolysis of carbon tetrachloride in the presence of a number of alkanes has been investigated in the gas phase. The products obtained from the photolysis experiments were those expected from a chain reaction in which trichloromethyl radicals abstract hydrogen atoms from the alkane. The data have been used to determine Arrhenius parameters for hydrogen abstraction from the series of alkanes CH4, CzH6, CzH8, and i-C4H1O by trichloromethyl radicals, ( 4 )

Reaction of methyl radicals with haloalkanes

“…We have recently studied the photolysis of CC1, in the presence of methane in the gas phase [4]. Methyl radicals in this system are produced via hydrogen atom abstraction from methane by either CC1, radicals or C1 atoms generated in the primary photolytic step.…”

The reaction of cyclopentyl radicals with carbon tetrachloride

“…However, Griller and Ingold [ 141 have used a competitive technique, involving direct measurements of radical concentrations by EPR spectroscopy, to show that the rate constant for bimolecular self-quenching of cyclopentyl radicals in solution is approximately equal to that for ethyl and isopropyl radicals. We have therefore assumed a value for kSc = L/mol-s independent of temperature and can hence derive k4 = 109.0*0. found previously for methyl, ethyl, and isopropyl radicals using the photolysis of CC4 as the radical source [4] (see values given in the Introduction).…”

“…Figure 2 shows an Arrhenius plot of the data for the rate constant ratio k4/k;L2 obtained from eq. (11) and provides an estimate of the rate parameters for chlorine atom abstraction from CCl4 by cyclopentyl radicals relative to those for cyclopentyl radical combination, k4/k i L2 = 104.1*0. found previously for methyl, ethyl, and isopropyl radicals using the photolysis of CC4 as the radical source [4] (see values given in the Introduction). The activation energy is also in reasonable agreement with the value of 11.8 kcal/mol determined in this laboratory for the cyclohexyl radical [8].…”

“…Assuming that the combination reaction is diffusion controlled, and that the activation energy of self-diffusion in n-hexane is 2.1 kcal/mol [3], values of A = 108.1 L/mol-s, E = 6.1 kcal/mol and of A = 108.3 L/mol-s, E = 6.1 kcal/mol can be estimated for chlorine atom abstraction by 2-hexyl and 3-hexyl radicals, respectively. We have recently studied the photolysis of CCl4 in the presence of several alkanes in the gas phase [4]. The alkyl radicals in this system are produced via hydrogen atom abstraction from the alkane by either trichloromethyl radicals or chlorine atoms generated in the primary photolytic step.…”

Kinetics and mechanism of the pyrolysis of 1-chloro-1,1-difluoroethane in the presence of additives

“…[16]. h From of the back-reaction has been estimated by means of the Polanyi-Evans method [17] using E for i E CCl ϩ C Cl : CCl ϩ C Cl и и [18] and the back-reactions of [19] and [20]. и и results as those in [3].…”