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MONOALKYL α‐OXOAMIDES: PHOTOCHEMISTRY IN HOMOGENEOUS and IN MICROHETEROGENEOUS MEDIA *
Author(s) -
Richard Wanda G.,
Chesta Carlos A.,
Whitten David G.
Publication year - 1991
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1991.tb02056.x
Subject(s) - chemistry , zwitterion , photochemistry , electron transfer , reactivity (psychology) , aqueous solution , quantum yield , diradical , quenching (fluorescence) , intramolecular force , ketone , excited state , stereochemistry , organic chemistry , singlet state , fluorescence , molecule , nuclear physics , medicine , physics , alternative medicine , pathology , quantum mechanics
An investigation of the photoreactivity of the amphiphilic α‐oxoamide, N‐(12‐dodecanoic acid)benzoylformamide, (1), in aqueous (pH 10) solution and its inclusion complexes with β‐cyclodextrin (β‐CD) and carboxymethylamylose (CMA). In all three media photolysis of 1 yields predominantly the fragmentation products from hydrolysis, mandelamide and the corresponding aldehyde. The most reasonable mechanism for the reaction is an intramolecular quenching of a ketone‐localized excited state by electron transfer from the amide nitrogen followed by proton transfer and a second electron transfer (zwitterion‐1 → diradical ⇄ zwitterion‐2) to yield ultimately the mandelamide‐imine precursor which hydrolyzes to the observed products. The quantum yields for 1 decomposition and mandelamide appearance in aqueous solution (pH 10) are 0.21 and 0.16, respectively. Compound 1 forms a 1:1 and 1:2 complex with β‐CD and shows enhanced quantum efficiencies for reaction, especially the 1:2 complex. 1 also forms a complex with CMA which shows a similar binding constant to other similar chain length amphiphiles in other studies. Here again reactivity is enhanced for the photoreaction of 1 upon complexation, indicating that neither the electron transfer quenching of the excited states nor reaction of subsequent intermediates is prohibited in the complexes. Mechanistic implications of these results are discussed.