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Protection of 4‐Fluoroanisole from Aromatic Nucleophilic Photosubstitution by Cyclodextrins [1]
Author(s) -
Liu Jerry H.,
Weiss Richard G.
Publication year - 1985
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.198500035
Subject(s) - chemistry , aqueous solution , cyclodextrin , nucleophile , photochemistry , nucleophilic substitution , quenching (fluorescence) , cyanide , reaction rate constant , nucleophilic aromatic substitution , fluorescence , medicinal chemistry , organic chemistry , kinetics , catalysis , physics , quantum mechanics
Aromatic nucleophilic photosubstitution reactions of 4‐fluoroanisole with cyanide and water have been investigated in aqueous α‐ β ‐, and γ‐cyclodextrin solutions. Although photoreactivity of the α‐ or β‐cyclodextrin‐complexed 4‐fluoroanisole toward nucleophilic substitution is suppressed almost completely, none of the cyclodextrins had a measurable influence on the rate of 4‐fluoroanisole fluorescence quenching by I − . In aqueous γ‐cyclodextrin, the efficiency of photohydroxylation was increased slightly but the efficiency of photocyanation was unaffected. From Benesi‐Hildebrand plots, the dissociation constants of the complexes of 4‐fluoroanisole with α‐ and β ‐cyclodextrins were obtained. A good correlation between the relative quantum yields and the degree of complexation was found. Explanation for the lack of a marked effect on photosubstitution by γ‐cyclodextrin is presented.