Rate constants for radical recombination. III. The trifluoromethyl radical

Hiatt, R.; Benson, Sidney W.

doi:10.1002/kin.550040502

Cited by 50 publications

(16 citation statements)

References 17 publications

(11 reference statements)

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“…Previous applications [l-41 of the method of free radical buffers [ I ] have shown rate constants for recombination of ethyl [ l , 41, isopropyl [2], and trifluoroniethyl [3] radicals to be significantly, but not dramatically, smaller than the constant for methyl radical recombination. For the tert-butyl radical, however, recent determinations combining kinetic and thermochemical analysis [5,61 have indicated a recombination constant some four orders of magnitude less than the previously accepted [7] value of Thus, investigation of a tert-butyl system by the radical buffer method has seemed especiaily pertinent, both as a further test of the technique and as an attempt to corroborate one or the other of the widely disparate values.…”

Section: Introductionmentioning

confidence: 99%

Rates of recombination of free radicals. V. The tert‐butyl radical

Hiatt

Benson

1973

Int J of Chemical Kinetics

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Analysis of the products from a vapor-phase mixture of EtI and t-BuI, in which free radicals were generated thermally, has yielded a rate constant for the recombination of Pt-Bu' of 105.4 M-' sec-' a t 100°C. The close agreement between this and other recent estimations from vapor-phase work is noted, as is the disparity between these values and those on the order of lo9 M-I sec-' obtained in solution.(3)If the [Et']/]t-Bu'] ratio is governed by eq. (l), it follows [ 11 that (5)

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Section: Introductionmentioning

confidence: 99%

Rates of recombination of free radicals. V. The tert‐butyl radical

Hiatt

Benson

1973

Int J of Chemical Kinetics

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“…21 Hiatt and Benson, using the ''buffer " technique with CH31 and CF31 coupled with thermochemical estimates of the equilibrium constant, find k6 to be in the range (1.8-15) x lo9 dm3 mol-' s-l at 146"C, depending on the thermochemical parameters. 22 Okafo and Whittle have recently given an improved value for D(CF3-I) and when this is applied to Hiatt and Benson's data, k6 values at the lower end of their range are…”

Section: Discussionmentioning

confidence: 99%

“…l7 It appears probable that the quantum yield of decomposition of CFJ is close to one and independent of temperature, like that of other iodoalkanes.' 22 Okafo and Whittle have recently given an improved value for D(CF3-I) and when this is applied to Hiatt and Benson's data, k6 values at the lower end of their range are Writing X, = [CF3CH2CH211 + [CF3CH=CH2] and Mo = initial ethylene concentration we have from the mechanism -dt Integration of this leads at once to the following expression, provided the rate of formation of C2F6 is independent of time, k2/@ = In [1 /(I -Xm/Mo)I/t@ (C2Ftj) where t is the time of photolysis of a given experiment.…”

Section: (8mentioning

confidence: 99%

Free radical addition to olefins. Part 19.—Trifluoromethyl radical addition to fluoro-substituted propenes and its absolute rate of addition to ethylene

Low¹,

Tedder²,

Walton³

1976

J. Chem. Soc., Faraday Trans. 1

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The rates of addition of trifluoromethyl radicals to each end of propene, l,l,l-trifluoropropene and hexafluoropropene have been determined using a competitive technique, taking as a standard the rate of addition to ethylene. The rate of addition of trifluoromethyl radicals to ethylene (2) has been compared with the rate of combination of trifluoromethyl radicals (6), and a value of kz/ki = (1.6 & 0.2) x lo3 exp (-2 900 f 500 cal mol-'/RT) dm3 mol-3 s* was determined (1 cal = J).CFs*+ CH2=CHz -+ CF3CHZCH2.(2) CFj*+ CF3* -+ C2Fe.kz ks Since the value of ks is now well established, a new value of the absolute rate of addition of trifluoromethyl radicals to ethylene and to the other olefins can be computed. EXPERIMENTAL Materials were obtained and purified as described previously,1o and were handled on a conventional mercury-free vacuum line. Reactions with ethylene, propene, 1,l ,I-trifluoropropene and hexafluoropropene were carried out in cylindrical Pyrex cells (1 85 and 237 cm3).

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“…The next gas-phase determination utilized the photochemical addition of bromotrichloromethane to ethylene 131. The initial photolytic step produces bromine atoms in addition to trichloromethyl Reference [17].…”

Section: Determination Of the Combination Of Trichloromethyl Radicalsmentioning

confidence: 99%

“…Recalculated from the original literature value using a value of k w 3 . = lo9-' l./molesec for the combination of CF, radicals (see [17]).…”

Section: Cc13brmentioning

confidence: 99%

ChemInform Abstract: THE REACTION OF TRICHLOROMETHYL RADICALS WITH HYDROGEN CHLORIDE AND A NEW ESTIMATION OF THE RATE OF COMBINATION OF TRICHLOROMETHYL RADICALS

Matheson¹,

Sidebottom²,

Tedder³

1974

Chemischer Informationsdienst

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The effect of the addition of hydrogen chloride on the photolysis of carbon tetrachloride in the presence of cyclohexane has been investigated in a companion paper. The data enable the rate constant ratio kg/(kJ1'2 to be determined. Since k-8 is well established, k5 can be estimated from known thermochemical data. The validity of the thermochemical derivation is checked by applying it to trifluoromethyl radicals. The photolysis of bromotrichloromethane and carbon tetrachloride in the presence of hydrogen chloride has been investigated over a range of temperatures. From these results and assuming reaction (5) has no activation energy, Arrhenius parameters for reaction (8) have been determined:The activation energies for the reaction of methyl, trichloromethyl, and trifluoromethyl radicals with hydrogen chloride are compared, and at first sight surprising results are rationalized in terms of relative electronegativity.(1 954).

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Rate constants for radical recombination. III. The trifluoromethyl radical

Cited by 50 publications

References 17 publications

Rates of recombination of free radicals. V. The tert‐butyl radical

Rates of recombination of free radicals. V. The tert‐butyl radical

Free radical addition to olefins. Part 19.—Trifluoromethyl radical addition to fluoro-substituted propenes and its absolute rate of addition to ethylene

ChemInform Abstract: THE REACTION OF TRICHLOROMETHYL RADICALS WITH HYDROGEN CHLORIDE AND A NEW ESTIMATION OF THE RATE OF COMBINATION OF TRICHLOROMETHYL RADICALS

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