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Photochemical transformations. 49. Solvent effects on singlet ionic and triplet photoreactions of some bridged polycyclic chlorides: Comparison with ground‐state reactions
Author(s) -
Cristol Stanley J.,
Plas Bart J. Vanden
Publication year - 1991
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.610040904
Subject(s) - chemistry , acetonitrile , cyclohexane , solvolysis , photochemistry , allylic rearrangement , solvent , singlet state , methylene , acetic acid , diene , singlet oxygen , photooxygenation , medicinal chemistry , triplet state , solvent effects , excited state , organic chemistry , hydrolysis , molecule , catalysis , physics , natural rubber , oxygen , nuclear physics
Direct irradiations of 2‐chloro‐6,7 : 8,9‐dibenzotricyclo [3.2.2.0 2,4 ] nona‐6,8‐diene (5‐Cl) were conducted in cyclohexane, acetic acid and wet acetonitrile. The products are 1‐methylfluoranthene (8) in all three solvents, the allylic chlorides 8‐chloro‐7‐methylene‐2,3 : 5,6‐dibenzobicyclo [2.2.2] octa‐2,5‐diene (3‐Cl) and 7‐chloromethyl‐2,3 : 5,6‐dibenzobicyclo [2.2.2] octa‐2,5,7‐triene (2‐Cl) in acetic acid and acetonitrile and solvolysis product amides in wet acetonitrile. Compound 5‐Cl had previously been shown to be the product of triplet sensitization of 2‐Cl and 3‐Cl, so that the singlet reaction reverses that of the triplet. The formation of 8 from 5‐Cl was quenched with piperylene, whereas that of the allylic chlorides was not. Quantum yields of products and singlet lifetimes in the three solvents were measured. The solvent effects are discussed. Deuterium‐labeling results on the formation of 5‐Cl from 2‐Cl and of 8 from 5‐Cl are reported.