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Fast reactions of polar molecules in processes with no activation energy
No full textThe rate constants of ion-molecule and radical recombination reactions involving polar species have been calculated using an intermolecular potential averaged over the molecular orientations. A transition state is proposed in which the two species are confined in a square potential well. The energy of the system within the well is then quantized. Calculations using the square potential well model show that electrostatic effects cannot be ignored for these polar species, and they give good agreement with experimental rate determinations.</p
Free radical addition to olefins. Part 3. - Addition of trichloromethyl radicals to propene, 2-fluoropropene and hexafluoropropene
No full textArrhenius parameters have been measured for the addition and hydrogen abstraction reactions of trichloromethyl radicals with propene, 2-fluoropropene, and hexafluoropropene.</p
Free-radical substitution in aliphatic compounds. Part XII. The chlorination of n-hexane in the gas and liquid phases
No full textn-Hexane has been chlorinated in the gas phase, with nitrogen as diluent, and in the liquid phase with carbon tetrachloride as a solvent. The relative rates of chlorination at the primary and secondary positions are given by the expressions (ks/kp)gas ≈ 2.2 ± 0.6 exp (214 ± 127 cal./RT) and (ks/kp) liquid = 0.8 ± 0.2 exp (597 ± 20 cal./RT). Possible explanations of this difference are discussed.</p
Free radical addition to olefins:Part 2. - Addition of trichloromethyl radicals to fluoroethylenes
No full textArrhenius parameters have been determined for the addition of trichloromethyl radicals to fluoroethylenes; for the unsymmfitric olefins the parameters have been determined for each end of the double bond. addition to CH2 addition to CHF addition to CF2 log A2 E2 log A2 E2 log A2 E2 CH2 = CH2 5.6 3.2 CFH = CH2 5.4 5.4 CF2 = CH 2 5.5 8.3 CH2 = CHF 5.5 3.3 CF2 = CHF 6.4 7.1 CH2 = CF2 5.7 4.6 CFH = CF2 6.3 6.1 CF 2 = CF2 7.1 6.1 (log A2 in 1. mole-1 sec-1; E2 in kcal mole-1) The determined activation energies are compared with localization energies, and with free valence as calculated from simple Hückel theory.</p
Free radical addition to olefins. Part 1. - Addition of bromotrichloromethane to ethylene
No full textThe light-induced addition of bromotrichloromethane to ethylene has been studied in a series of gas-phase experiments in which relative concentration, temperature and light intensity have been varied. The reaction is shown to involve the following process. CCl3+hv→CCl3· +Br· (1) CCl3·+E→CCl3E· (2) CCl3E·+CCl3Br→CC3EBr+CCl 3· (3) CCl3·+CCl3·→ C2Cl6 (4) Br·+E→EBr· (5) CCl 3·+CCl3·→(CCl3E) 2. (7) When bromotrichloromethane is in excess, reaction (4) is the predominant chain-termination process, and using literature data for k 4, the value k2 = 4.17×105 exp (-3240/RT)l. mole-1 sec-1 was determined. With ethylene in large excess, reaction (7) becomes the main chain termination process, and assuming A7≈108 and E7≈0, the value k3≈105 exp (-3400/RT)l. mole-1 sec -1 was determined.</p
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