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Der ‘Push-Pull’-Effekt von ‘Push-Pull’-Oligoacetylenen. Eine 13C-NMR-Untersuchung

✍ Scribed by Markus Neuenschwander; Andreas Bartlome

Publisher
John Wiley and Sons
Year
1991
Tongue
German
Weight
604 KB
Volume
74
Category
Article
ISSN
0018-019X

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✦ Synopsis

The 'Push-Pull' Effect of 'Push-Pull' Oligoacetylenes. A I3C-NMR Investigation According to 13C-chemical shifts of 'push-pull' oligoacetylenes 14, the 'push-pull' effect (i.e. A delocalization induced by 'push-pull' substituents) rapidly decays in this series. To correct for other than n-charge-density effects, A6 values of symmetrically placed C-atoms of the oligoacetylene chain are discussed. Stereoelectronic resteffects (SER) of the substituents on terminal C-atoms of PP-ketones la-3a and PP-esters 1 W b are estimated from the residual A6 of the asymptotes of Fig. 3. Fig. 4 convincingly shows that A6 values are dramatically decreasing with increasing number n of acetylene units between the push and pull substituents. Assignment problems of 'push-pull' triacetylenes 3 have been solved by I3C labelling of the CO group of 3a.

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Teil der Dissertation 121.

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