Formation of 3,6-di-tert-butyl-2-hydroxyphenoxyl radicals upon the inhibition of polymerization of methyl methacrylate by the system containing 3,6-di-tert-butylpryocatechol and 3,6-di-tert-butyl-1,2-benzoquinone

Conclusions 3,6-Di-tert-butyl-2-hydroxyphenoxyl radicals (QH^.) were detected by EPR spectroscopy in a mixture of 3,6-di-tert-butylpyrocatechol (QH₂) and 3,6-di-tert-butyl-1,2-benzoquinone (Q) in the polymerization of methyl methacrylate. The rate constant for the reaction QH₂ + Q 2QH^. and the rate contants for the forward and back reactions were determined at 60°C.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1188–1190, May, 1989.The authors express their gratitute to Ya. S. Lebedev for a discussion of this work.     

Kinetic study of the protolysis of 2,6-di-tert-butyl-4-hydroxyphenoxyl

The kinetic acidity of 2,6-di-tert-butyl-4-hydroxyphenoxyl in tetrahydrofuran has been estimated by means of ESR. It is shown that ion pairs are formed in the process of proton transfer from the radical to triethylamine.A. N. Nesmeyanov Institute of Heteroorganic Compounds, Russian Academy of Sciences, 117813 Moscow. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 11, pp. 2512–2516, November, 1992.     

Dynamic effects in ESR spectra of 4-triphenylmethyl-6-tert-butyl-2-hydroxyphenoxyl and 4-triphenylmethyl-6-phenyl-2-hydroxyphenoxyl

Conclusions In the ESR spectra of 6-triphenylmethyl-4-tert-butyl-2-hydroxyphenoxyl and 6-triphenylmethyl-4-phenyl-2-hydroxyphenoxyl and their deuterated analogs, temperature-dependent dynamic effects have been found; these are explained from the standpoint of a reversible intramolecular transition between different conformations of the radicals, differing in the spin density distribution, owing to direct interaction of the unpaired electron with the orbitals of the phenyl rings of the triphenylmethyl substituent.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1513–1517, July, 1985.     

The reaction of 3,6-di-tert-butyl-1,2-benzoquinone and 3,6-di-tert-butylcatechol withtert-butyl hydroperoxide

Reaction of 3,6-di-tert-butyl-1,2-benzoquinone and 3,6-di-tert-butylcatechol withtert-butyl hydroperoxide in aprotic solvents leads to the generation of semiquinone (SQ^.H), alkylperoxy (ROO^.), and alkyloxy radicals. The reaction of SQ^.H and ROO^. produces 2,5-di-tert-butyl-6-hydroxy-1,4-benzoquinone, 3,6-di-tert-butyl-1-oxacyclohepta-3,5-diene-2,7-dione, and 2,5-di-tert-butyl-3,6-dihydroxy-1,4-benzoquinone. The radical generated from solvent attacks SQ^.H at position 4 with C−C bond formation. 4-Benzyl-2,5-di-tert-butyl-6-hydroxycyclohexa-2,5-diene-1-dione produced in this way is transformed into 4-benzyl-3,6-di-tert-butyl-1,2-benzoquinone under the reaction conditions. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 943–946, May, 1999.