Spectroscopic CNDO/CI study of some cyclic polyenes

✍ Scribed by Felice Zuccarello; Giuseppe Buemi; Antonio Raudino

• Publisher: John Wiley and Sons
• Year: 1980
• Tongue: English
• Weight: 516 KB
• Volume: 1
• Category: Article
• ISSN: 0192-8651
• DOI: 10.1002/jcc.540010405

✦ Synopsis

Abstract

CNDO/S calculations are carried out on 1,3,5‐cycloheptatriene (I), 1,3,5,7‐cyclooctatetraene (II), all‐cis‐1,3,5,7‐cyclononatetraene (III), and all‐cis‐1,4,7‐cyclononatriene (IV), for which π‐σ separability is a questionable matter. When disparate choices are available for the geometries, preferences are based on the agreement between calculated and experimental spectra. The microwave structure for I and an unsymmetrical conformation for III are suggested. In the electronic spectra, conjugative contributions are assigned to the lowest‐energy weak band, while an ethylenic nature is to be attributed to the intense band in the range of 6 eV. The possibility of through‐space π interactions is examined qualitatively. An appreciable degree of such interaction is shown by IV.