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Mechanisms of Photochemical Reactions in Solution. LXXIV. The Photochemistry of 3‐Methyl‐1‐Phenoxybut‐2‐Ene. ,
Author(s) -
Carroll Felix A.,
Hammond George S.
Publication year - 1972
Publication title -
israel journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 54
eISSN - 1869-5868
pISSN - 0021-2148
DOI - 10.1002/ijch.197200059
Subject(s) - chemistry , photochemistry , homolysis , intersystem crossing , singlet state , radical , dissociation (chemistry) , chromophore , excited state , triplet state , population , ether , ene reaction , bond cleavage , medicinal chemistry , catalysis , molecule , organic chemistry , physics , demography , sociology , nuclear physics
The photochemical reactions of 3‐methyl‐1‐phenoxybut‐2‐ene ( γ,γ ‐dimethylallyl phenyl ether), I, were investigated in solution and in the gas phase. Irradiation of I resulted in the formation of phenol, II, 3‐methyl‐3‐phenoxybutene, III, 1‐(2‐hydroxyphenyl)‐3‐methylbut‐2‐ene, IV, 1‐(4‐hydroxyphenyl)‐3‐methylbut‐2‐ene, V, 3‐(2‐hydroxyphenyl)‐3‐methylbutene, VI, and 3‐(4‐hydroxyphenyl)‐3‐methylbutene, VII. Formation of III ‐ VII in the gas phase was efficiently quenched by nitric oxide. The results suggest that all products were formed by a dissociation ‐ radical recombination mechanism and that none were formed by concerted processes. The absorption spectrum of I and its quantum yields for fluorescence and photochemical reaction were used to estimate the rates of the processes which deactivate its lowest‐lying excited singlet state. The results suggest that OC bond homolysis need not occur via intersystem crossing from an S 1 ( π , π *) to a 3 σ (CO) state. Fragmentation to radicals, and perhaps rapid non‐radiative decay without chemical reaction, probably involve internal conversion with population of high vibrational levels of the CO bond. Weak electronic interaction between the aromatic nucleus and the olefinic chromophore may also be important.