Abstract
The 13C FT NMR spectra of phenylacetylene (1), p-methoxyphenylacetylene (2), p-fluorophenyl-acetylene (3), p-chlorophenylacetylene (4), p-bromophenylacetylene (5), p-ethylphenylacetylene (6) and p-isopropylphenylacetylene (7) as well as of a number of monosubstituted benzenes have been measured. The 13 C-chemical shifts in these compounds are correlated with the total charge densities at the corresponding carbon atoms, calculated by the CNDO/2 method. The present results show that a simple additivity exists between 13C-chemical shifts in substituted benzenes, phenylacetylene and substituted phenylacetylenes and that practically no charge transfer between the linked sub-stituted phenyl and the ethinyl groups takes place. The interaction of the ethinyl substituent and the π-electron system can mainly be attributed to inductive effects.
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