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Cage reactions in the photolysis of 2,2,4,4‐tetramethyl‐3‐pentanone
Author(s) -
Abuin E. B.,
Encinas M. V.,
Díaz S.,
Lissi E. A.
Publication year - 1984
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.550160502
Subject(s) - chemistry , disproportionation , propionaldehyde , radical , photodissociation , quantum yield , photochemistry , cage effect , micelle , micellar solutions , organic chemistry , catalysis , aqueous solution , aldehyde , physics , quantum mechanics , fluorescence
The product quantum yields in the photolysis of 2,2,4,4‐tetramethyl‐3‐pentanone have been measured in homogeneous solvents of different viscosities, in micellar solutions of cetyltrimethylammonium chloride and sodium dodecyl sulfate, and in dioctadecyl ammonium chloride vesicles. The product quantum yield in n ‐heptane was found to be 1. This value decreases to 0.5 in paraffin oil as a consequence of geminate recombination. In the presence of free radical scavengers, the extent of geminate disproportionation can be evaluated from the yields of isobutene and 2,2‐dimethyl propionaldehyde. From these yields and the geminate recombination yields the total amount of geminate processes and the disproportionation‐to‐combination ratio for caged radicals are estimated. It is found that micelles provide the most efficient cages. In these media only about 10% of the radicals avoid cage processes. The disproportionation‐to‐combination ratio of tert‐butyl and pivaloyl radicals was found to be extremely media dependent. The measured values ranged from about 0.2 in paraffin oil to 0.8 in cetyltrimethylammonium chloride micelles.