31987-29-8Relevant academic research and scientific papers
Pentamethyldisilyl Radical: Absolute Rate Constants for Its Formation and for Some Halogen Abstraction and Addition Reactions
Lusztyk, J.,Maillard, B.,Ingold, K. U.
, p. 2457 - 2460 (1986)
Pentamethyldisilane is a better hydrogen donor than Et3SiH toward tert-butoxyl (k's for the overall reaction are 17 and 5.7 * 106 M-1 s-1, respectively, at ca. 27 deg C) and toward primary alkyl radicals (k's for Si-H bond cleavage are ca. 10 and 1.0 * 104 M-1 s-1, respectively, at 120 deg C).Absolute rate constants for various reactions of the Me3SiSiMe2 radical have been measured by laser flash photolysis at room temperature.In halogen atom abstractions, for example, the Me3SiSiMe2 radical is slightly less reactive than Et3Si, but it is more reactive than n-Bu3Ge and n-Bu3Sn.Pentamethyldisilane would appear to offer an attractive alternative to n-Bu3SnH and n-Bu3GeH in radical chain reactions in which the desired product is formed by a hydrogen transfer not to the organic radical formed initially but to a second radical formed by a slow β-scission or rearrangement of the initial radical.
Absolute rate constants for the β-scission and hydrogen abstraction reactions of the tert-butoxyl radical and for several radical rearrangements: Evaluating delayed radical formations by time-resolved electron spin resonance
Weber, Matthias,Fischer, Hanns
, p. 7381 - 7388 (2007/10/03)
An analysis is presented for the determination of absolute rate constants for radical transformation reactions in complex reaction systems by time-resolved ESR during intermittent photochemical radical production. The technique is applied to obtain absolu
Kinetics of the 1,2-Migration of Carbon-Centered Groups in 2-Substituted 2,2-Dimethylethyl Radicals
Lindsay, D. A.,Lusztyk, J.,Ingold, K. U.
, p. 7087 - 7093 (2007/10/02)
The rearrangements RCMe2CH2. -> RCH2C.Me2 (kr) (R = Ph, Me3CCC, Me3CC=O, and NC) have been studied over a range of temperatures by product analyses with use of the common competiting reaction RCMe2CH2. + CCl4 -> RCMe2CH2Cl + CCl3. (kCl).For R = H2C=CH the rearrangement was so fast that only the rearranged chloride, RCH2CMe2Cl, was produced.All these rearrangements occur via a 3-membered cyclic intermediate radical (or transition state).Various considerations led to the following Arrhenius equation for chlorine abstraction: log (kCl/M-1 s-1)=(8.14 +/- 0.42)-(5.52 +/- 0.63)/τ, where τ=2.3RT kcal/mol, and this equation is used to calculate Arrhenius parameters for migration of all but the H2C=CH group.Comparison of these parameters with those already available from kinetic EPR measurements leads to a choice of preferred Arrhenius parameters for all five rearrangements.The cyano group had an unexpectedly low mobility while the pivaloyl group underwent a surprisingly rapid 1,2-shift.Migratory aptitudes increase along the series R = NC C r at 25 deg C = 0.9, 93, 762, 1.7*105, and 1.0 * 107 s-1, respectively.The preferred pre-exponential factors all lie in the range 1010.9 - 1012.0, while the activation energies vary from 16.4 kcal/mol for R = NC to 5.7 kcal/mol for R = H2C=CH.These results are discussed in relation to the results of thermochemical kinetic calculations and to earlier work on the 1,2-migration of unsaturated groups in radicals.
