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Peresters XIII. Solvent effects in the decomposition of t ‐butylperoxy α‐phenylisobutyrate with special reference to the cage effect
Author(s) -
Herkes Frank E.,
Friedman Juliette,
Bartlett Paul D.
Publication year - 1969
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.550010206
Subject(s) - chemistry , cage effect , radical , solvent , cage , decomposition , reaction rate constant , solvent effects , photochemistry , organic chemistry , kinetics , physics , mathematics , combinatorics , quantum mechanics , photodissociation
t ‐Butylperoxy α‐phenylisobutyrate ( I ) decomposes thermally by concerted formation of carbon dioxide, t ‐butoxy, and cumyl radicals. Radical pair return in the solvent cage therefore does not affect the observed rate of decomposition, but is readily determined by means of galvinoxyl and other scavengers. In a series of 15 solvents the rate constant varies over a 2.8 fold range, being fastest in aromatic solvents. In the same solvent series the relative rates of diffusion and combination of radicals, measured by the cage effect, change by tenfold and are largely determined by the viscosity of the solvent. In all solvents of η > 8 mP, the reciprocal of the cage effect is a linear function of ( T 1/2 /η), as recently observed for trifluoromethyl and methyl radicals [16]. This property of the cage effect provides a test by which it can be distinguished from other processes that reduce the efficiency of free‐radical production from an initiator.