35336-99-3Relevant academic research and scientific papers
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 (1984)
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.
