51391-19-6Relevant academic research and scientific papers
E.S.R. Spectra of Free Radicals Relevant to Methacrylate Polymerization
Keah, Hooi Hong,Rae, Ian D.,Hawthorne, David G.
, p. 659 - 669 (2007/10/02)
Carbon-based free radicals were generated by thermal cleavage of the tetraester Me2C(COOMe)-CH2-CMe(COOMe)-CMe(COOMe)-CH2-C(COOMe)Me2 which is a model for head-to-head units in a poly(methyl methacrylate) chain.The resulting electron spin resonance spectrum had higher resolution than the 'nine-line' spectrum previously reported; this enabled identification of the component radicals.In the present case, the spectrum was well matched by a summation of spectra of the Me2C(COOMe)-CH2-CMe(COOMe) radical and the 1-methoxycarbonyl-1-methylethyl radical Me2-C-COOMe derived from it by loss of methyl methacrylate.Both of these radicals were generated in separate experiments.Radicals were also generated from starting materials containing a CD3 group in place of the single CH3.
Destabilized Carbenium Ions: α-Carbomethoxy-α,α-dimethyl-methyl Cations
Wolf, Rainer,Gruetzmacher, Hans-Fr.
, p. 398 - 404 (2007/10/02)
Tertiary α-carbomethoxy-α,α-dimethyl-methyl cations a have been generated by electron impact induced fragmentation from the appropriately α-substituted methyl isobutyrates 1-4.The destabilized carbenium ions a can be distinguished from their more stable isomers protonated methyl methacrylate c and protonated methyl crotonate d by MIKE and CA spectra.The loss of I. and Br. from the molecular ions of 1 and 2, respectively, predominantly gives rise to the destabilized ions a, whereas loss of Cl. from +. results in a mixture of ions a and c.The loss of CH3. from +. favours skeletal rearrangement leading to ions d.The characteristic reactions of the destabilized ions a are the loss of CO and elimination of methanol.The loss of CO is associated by a very large KER and non-statistical kinetic energy release (T50 = 920 meV).Specific deuterium labelling experiments indicate that the α-carbomethoxy-α,α-dimethyl-methyl cations a rearrange via a 1,4-H shift into the carbonyl protonated methyl methacrylate c and eventually into the alkyl-O protonated methyl methacrylate before the loss of methanol.The hydrogen rearrangements exhibit a deuterium isotope effect indicating substantial energy barriers between the + isomers.Thus the destabilized carbenium ion a exists as a kinetically stable species within a potential energy well.
