Radiation‐induced dechlorination of carbon tetrachloride in cyclohexane Solutions. The kinetics of liquid‐phase reactions of trichloromethyl radicals

Abstract

The kinetics of the gamma-radiation induced free-radical chain reaction in solutions of carbon tetrachloride in cyclohexane (RH) has been investigated in the temperature range of 303-383'K.Trichloromethyl radicals were produced by the reaction of radiolytically generated cyclohexyl radicals with carbon tetrachloride. The kinetics of the following reactions were investigated:The following rate expression was obtained: log k 3 / ( k 4 ) l l Z (cm3~2/mo1e1~2~sec1~2) = 4.78 f 0.08 -(8.81 f 0.12)/01The error limits are the standard deviation from the least mean square Arrhenius plots. Effects of phase on the kinetics of reactions (3) and (4) are considered.

Rate constants for the combination of trichloromethyl radicals and the electron‐transfer reaction between hydroxymethyl radicals and carbon tetrachloride in solution

“…Griller and Ingold [6] found at room temperature in n-pentane a ratio of k&g = 0.4 f 0.3 for 2kc relative to the self-termination rate constant k g of tert-butyl rad- Switzerland. icals, which should amount to 2 k~ N 1O1O M-l-sec-l under these conditions [9,12]. Furthermore, Katz and co-workers [19] concluded from the kinetics of the chain reaction between trichloromethyl radicals and n-hexane in a hexane-carbon tetrachloride solvent mixture that 2kc is very probably temperature-and viscosity-dependent. Finally, in one of the earlier studies, Carlsson and co-workers [20] reported 2kc = 1.2 X lo9 A4-l.sec-l at T = 25OC in cyclohexane.…”

Free radical decomposition of bromoacetonitrile in liquid cyclohexane

“…The expected opposite effect was observed foy hydrogen abstraction from cyclopentane and cyclohexane by the CClzCN radicals [3]. In this case the reaction of the cyano substituted radical appears to require a higher activation energy than the analogous reaction of the CC13 radical [5]. Both effects reflect the stability of the cyano substituted radicals which also reduced bond strengths in the parent compounds from which these radicals are derived.…”

The reaction of cyclopentyl radicals with carbon tetrachloride

“…Dutsch and Fischer [7] have previously suggested that the increase in the rate of chlorine atom transfer with increasing a-alkyl substitution of the radical in solution can be attributed to the contribution of highly polarized structures to the transition state, the importance of which increases with increasing a-alkyl substitution. It is of interest to note that Rajbenbach and co-workers [15,16] and Alfassi and Feldman [17] have shown that the activation energies for hydrogen atom abstraction from alkanes by trichloromethyl radicals in the solution phase are approximately equal to the corresponding values determined in the gas phase. Thus solvation of the transition state for the transfer of a hydrogen atom from an alkane to the CCl3 radical cannot be significantly different from the solvation of the reactants, at least in nonpolar solvents.…”