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185‐nm Photochemistry of Olefins, Strained Hydrocarbons, and Azoalkanes in Solution
Author(s) -
Adam Waldemar,
Oppenländer Thomas
Publication year - 1986
Publication title -
angewandte chemie international edition in english
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 0570-0833
DOI - 10.1002/anie.198606613
Subject(s) - photochemistry , chemistry , intramolecular force , photodissociation , isomerization , excited state , singlet state , chromophore , photoisomerization , catalysis , organic chemistry , physics , nuclear physics
The possibility to excite directly at 185 nm chromophores that absorb in the vacuum‐UV has stimulated increased activity during the last decade in this field of photochemistry. Whereas photochemical reactions at λ<200 nm have been thoroughly investigated in the gas phase, only recently have intensive studies on the 185‐nm photochemistry of organic compounds in solution provided new insights. Despite the high excitation energies, selective photoreactions are promoted in the short‐lived singlet excited states (Rydberg photochemistry). In contrast to conventional photochemistry (λ > 220 nm), 185‐nm irradiation preferentially results in intramolecular rearrangement, fragmentation, and isomerization reactions. Intermolecular radical couplings and abstractions as well as dimerizations (π, π * ‐excitation) compete minimally. Besides the straightforward denitrogenation of photoresistant (“reluctant”) azoalkanes, important applications of the short‐wavelength photolysis are also found in technology (photolithography) and medicine (193‐nm laser). Broadening the scope of the synthetic potential of the 185‐nm photochemistry, which so far has been limited to direct cis/trans isomerizations, presents a challenge for the chemist.