93524-81-3Relevant articles and documents
A novel organic peroxyester as an exclusive source of tert-butyl radicals
Nakamura, Tomoyuki,Watanabe, Yasumasa,Tezuka, Hiroshi,Busfield, W. Ken,Jenkins, Ian D.,Rizzardo, Ezio,Thang, San H.,Suyama, Shuji
, p. 1093 - 1094 (1997)
A novel peroxyester, 1,1,2,2-tetramethylpropyl peroxypivalate 1b, has been synthesized and thermolyzed in cumene. The kinetic data show that the decomposition rate constant of 1b is about three times higher than that of tert-butyl peroxypivalate. The radical trapping technique employing 1,1,3,3-tetramethyl-2,3-dihydro-1H-isoindol-2-yloxyl has been used to study the decomposition mechanism of 1b. The results show that the thermolysis of 1b in cumene generates tert-butyl radicals exclusively.
Thermal decomposition mechanisms of tert-alkyl peroxypivalates studied by the nitroxide radical trapping technique
Nakamura,Busfield,Jenkins,Rizzardo,Thang,Suyama
, p. 16 - 23 (2007/10/03)
The thermolysis of a series of tert-alkyl peroxypivalates 1 in cumene has been investigated by using the nitroxide radical-trapping technique. tert-Alkoxyl radicals generated from the thermolysis underwent the unimolecular reactions, β-scission, and 1,5-H shift, competing with hydrogen abstraction from cumene. The absolute rate constants for β-scission of tert- alkoxyl radicals, which vary over 4 orders of magnitude, indicate the vastly different behavior of alkoxyl radicals. However, the radical generation efficiencies of 1 varied only slightly, from 53 (R = Me) to 63% (R = Bu(t)), supporting a mechanism involving concerted two-bond scission within the solvent cage to generate the tert-butyl radical, CO2, and an alkoxyl radical. The thermolysis rate constants of tert-alkyl peroxypivalates 1 were influenced by both inductive and steric effects [Taft-Ingold equation, log(rel k(d)) = (0.97 ± 0.14)Σσ* - (0.31 ± 0.04)ΣE(s)(c), was obtained].
Thermal decomposition of 1-cyclohexyl-1-methylethyl peroxypivalate
Nakamura, Tomoyuki,Busfield, W. Ken,Jenkins, Ian D.,Rizzardo, Ezio,Thang, San H.,Suyama, Shuji
, p. 965 - 966 (2007/10/03)
The thermal decomposition of a novel peroxyester, 1-cyclohexyl-1-methylethyl peroxypivalate 1a in cumene has been studied using the radical trapping technique employing 1,1,3,3-tetramethyl-2,3-dihydro-1H-isoindol-2-yloxyl T, a stable aminoxyl radical, as
Free radical initiation mechanisms in the polymerization of methyl methacrylate and styrene with 1,1,3,3-tetramethylbutyl peroxypivalate: Addition of neopentyl radicals
Nakamura, Tomoyuki,Busfield, W. Ken,Jenkins, Ian D.,Rizzardo, Ezio,Thang, San H.,Suyama, Shuji
, p. 10987 - 10991 (2007/10/03)
The reactions of 1,1,3,3-tetramethylbutyl (tert-octyl) peroxypivalate (1) with methyl methacrylate (MMA) and styrene in the presence of the free radical scavenger 1,1,3,3-tetramethyl-2,3-dihydro-1H-isoindol-2-yloxyl (2) have been studied at 60°C. tert-Butyl and tert-octyloxyl radicals (3) were generated from the thermolysis of 1. The predominant unimolecular reactions of 3, that is, β-scission to form neopentyl radicals (14b) and a 1,5-H shift to form 4-hydroxy-2,2,4-trimethylpentyl radicals (14c), were observed in both monomer systems. The resulting alkyl radicals underwent selective addition to the two monomers. The relative reactivities of the alkyl radicals toward addition to the monomers were obtained from competitive addition/trapping reactions. The absolute rate constants for the addition of alkyl radicals 14b and 14e to the two monomers at 60°C were estimated to be 9.5 x 105 and 2.6 x 105 M-1 s-1 to MMA and 4.5 x 105 and 0.7 x 105 M-1 s-1 to styrene, respectively. The low reactivities of 3 and 14e toward addition to MMA and styrene were attributed to steric effects. Steric effects were also responsible for the low rate of the 1,5-H shift in 3.
Reaction of tert-alkoxyl and alkyl radicals with styrene studied by the nitroxide radical-trapping technique
Nakamura, Tomoyuki,Busfield, W. Ken,Jenkins, Ian D.,Rizzardo, Ezio,Thang, San H.,Suyama, Shuji
, p. 5578 - 5582 (2007/10/03)
The reactions of tert-alkyl peroxypivalates 1 (R = methyl, ethyl, and n- propyl) with styrene in the presence of the free-radical scavenger (1,1,3,3- tetramethyl-2,3-dihydro-1H-isoindol-2-yl)oxyl (2) have been studied at 60 °C. tert-Butyl and tert-alkoxyl radicals (tert-butoxyl, tert-pentyloxyl, and tert-hexyloxyl radicals) were generated from the thermolysis of 1, and the derivative alkyl radicals (methyl, ethyl, n-propyl, and 4-hydroxy-4- methylpentyl radicals) were formed by subsequent unimolecular reactions (β- scission and 1,5-H shift) of the corresponding tert-alkoxyl radicals. The extent of the unimolecular reactions of the tert-alkoxyl radicals (versus addition to styrene) and the relative reactivity of alkyl radicals toward addition to styrene were obtained from the competitive addition/trapping reactions. The absolute rate constants for the addition of tert-butyl, ethyl, methyl, and n-propyl radicals to styrene at 60 °C were estimated to be (7.4, 4.7, 5, and 5.4) x 105 M-1 s-1, respectively.
RECTIONS OF HYDROXYL RADICALS WITH POLYMERIZABLE OLEFINS
Grant, Richard D.,Rizzardo, Ezio,Solomon, David H.
, p. 379 - 384 (2007/10/02)
The reactions of hydroxyl radicals with methyl acrylate, methyl methacrylate, styrene, and α-methylstyrene have been investigated by a trapping technique which uses 1,1,3,3-tetramethylisoindolin-2-yloxyl (1) as a radical scavenger.The major reaction pathway in each case was addition to the unsubstituted (tail) end of the monomer, although addition to the substituted (head) end and reaction with the double-bond substituents were also observed.Absolute rates of reaction were estimated by means of competition experiments using cyclohexane as reference substrate.The implications of the results for the structure of polymers initiated by hydroxyl radicals are discussed.
2-(t-Butylazo)prop-2-yl Hydroperoxide: A Convenient Source of Hydroxyl Radicals in Organic Media
Grant, Richard D.,Rizzardo, Ezio,Solomon, David H.
, p. 867 - 868 (2007/10/02)
In the presence of a suitable nitroxide, 2-(t-butylazo)prop-2-yl hydroperoxide (1a) decomposes cleanly into hydroxyl and t-butyl radicals; the rate constant for its disappearance in cyclohexane is given by: k = 9.58*1014 exp.(-1.47*104/T)s-1.
