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Photodimerization of Solid Pleiadiene; Isomerization and Cycloreversion of the Dimer

✍ Scribed by Alan C. Hazell; Richard M. Pagni; Gabriele Persy; Erika Rommel; Jakob Wirz

Book ID
102856649
Publisher
John Wiley and Sons
Year
1981
Tongue
German
Weight
575 KB
Volume
64
Category
Article
ISSN
0018-019X

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✦ Synopsis

Irradiation (Iu> 400 nm) of solid pleiadiene (1) yields a single, head-to-head [,4, + r4,]-photodimer (2) the structure of which was determined by X-ray analysis.

The formation of 2 is entirely suppressed at 77 K, since properly oriented pairs of molecules arise only from thermal disorder in crystals of 1. Upon pyrolysis (80"), the strained photodimer 2 rearranges to the [,2,+.4,] dimer 3 by a 'forbidden' suprafacial [1,3]-C-atom migration. Both 2 and 3 are reconverted to 1 by UV. irradiation in solution, but the latter, 'forbidden' photoreaction is suppressed at 77 K. Discrepancies of the experimental observations with the predictive schemes of Kaupp or Michl are discussed. ' I )

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## Abstract Mass spectrometry‐based methods have been employed in order to study the reactions of non‐ (__h__~6~/__h__~6~), half (__d__~6~/__h__~6~), and fully (__d__~6~/__d__~6~) deuterium labeled protonated dimers of acetone in the gas phase. Neither kinetic nor thermodynamic isotope effects were