Beiträge zur Chemie der Pyrrolpigmente, 11. Mitt.: Die Lichtabsorption geometrisch isomerer Arylmethyliden-pyrrolinone —Konformationsanalytische Studien |
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Authors: | Doz. Dr. Heinz Falk Karl Grubmayr Otmar Hofer Franz Neufingerl |
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Affiliation: | 1. Lehrkanzel für Organische Chemie der Universit?t Wien, W?hringer Stra?e 38, A-1090, Wien, ?sterreich
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Abstract: | By investigation of the geometrical isomers of several substituted arylmethylidene-pyrrolinones using lanthanide induced shift experiments in connection with a computer program, the ring current model,PPP—SCF—LCAO—MO—CI calculations and UV spectroscopy the following conclusions could be drawn: The light absorptions ofZ- andE-isomers vary only in the case of different dihedral angles at the arylmethine bond. The dihedral angles in theE-isomers are determined by the substituent in 4-position of the lactam ring. Hydrogen makes no difference whereas methyl leads to a more twistedE-structure which therefore shows a marked hypsochromic shift of the intense long wavelength absorption band, as compared to the correspondingZ-isomer. |
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