ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The photoelectron spectra of 1,5-cyclooctadiyne (2) and of 1,6-dithiacyclodeca-3,8-diyne (3) have been recorded. The first four (2) or six (3) PE. bands have been assigned as follows; in increasing order of ionization potentials: \documentclass{article}\pagestyle{empty}\begin{document}$$ 2:\,2{\rm b}_{{\rm 2g}} (\pi),\,6{\rm b}_{{\rm 1u}} (\pi),\,7{\rm a}_{\rm g} (\pi),\,2{\rm b}_{{\rm 3u}} (\pi) $$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$ 3:\,14{\rm a}_{\rm g} ({\rm n}),\,9{\rm a}_{\rm u} (\pi),\,13{\rm b}_{\rm u} ({\rm n}),\,12{\rm b}_{\rm u} (\pi),\,8{\rm b}_{\rm g} (\pi),\,13{\rm a}_{\rm g} (\pi) $$\end{document}The relative sequence and the positions of the PE. bands are explained in terms of through-bond and through-space interactions between the basis π-orbitals and σ-orbitals of appropriate symmetry behaviour.An analysis of the PE. spectroscopic data for cyclooctyne (1) and for (2) indicates that a cis-bend of the acetylene moiety by θ 〈 20° leads to a split in energy of the in-plane and out-of-plane basis π-orbitals which is smaller than ∽ 0.2 eV. This is in agreement with the predictions derived from semiempirical models (MINDO/2, SPINDO) and qualitative orbital arguments. However, it is shown by using orbital localization procedures, that the rationales underlying the two semiempirical models differ significantly.
Additional Material:
8 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19740570504
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