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Photo Valence Isomerization of 8,9‐Bis( N ‐cyclohexylcarbamoyloxymethyl)‐[6]paracyclophane
Author(s) -
Bockisch Frank,
Dreeskamp Herbert,
Von Haugwitz Thilo,
Tochtermann Werner
Publication year - 1991
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19911240821
Subject(s) - chemistry , isomerization , heptane , quantum yield , photostationary state , valence (chemistry) , irradiation , yield (engineering) , arrhenius equation , photochemistry , wavelength , medicinal chemistry , activation energy , organic chemistry , thermodynamics , photoisomerization , catalysis , physics , quantum mechanics , nuclear physics , fluorescence , optoelectronics
Irradiation in the wavelength range of λ = 270 ‐ 320 nm of 8,9 ‐bis( N ‐cyclohexylcarbamoyloxymethyl)‐[ 6 ]paracyclophane( 1b ) in dilute fluid solutions produces the 1,4‐Dewar isomer 2b in a quantum yield of 2.8% while the quantum yield of the rearomatization is 19% in heptane at room temperature. A photostationary equilibrium may be attained which depends strongly on the wavelength of irradiation. At λ = 290 nm 76% of the [6]paracyclophane isomer 1b is obtained whereas at λ = 310 nm 83% of the Dewar isomer 2b is formed in ethanol. The thermal back reaction 2b → 1b follows the Arrhenius law (E a = 95.9 ± 4.0 kJ/mol, lg A = 10.6 ± 0.4 in heptane). By irradiating 1b with λ < 270 nm the prismane isomer 3b is formed via the Dewar isomer 2b .