%0 Journal Article
%T Effect of substituents on the 13C-NMR chemical shifts of 3-methylene-4-substituted-1,4-pentadienes. Part I.
%A NATASA V. VALENTIC
%A ZELJKO VITNIK
%A SERGEI I. KOZHUSHKOV
%A ARMIN DE MEIJERE
%J Journal of the Serbian Chemical Society
%D 2003
%I Serbian Chemical Society
%X The principles of linear free energy relationships were applied to the 13C substituent chemical shifts (SCS) of the carbon atoms in the unsaturated chain of 3-methylene-4-substituted-1,4-pentadienes. Correlations of the SCS with the substituent parameters of Swain and Lupton provide a mutually consistent picture of the electronic effects in these compounds. The pattern of the electronic effects can be fully rationalized by a model based on the direct transmission of substituent effects through-space (direct through-space field effects), and via conjugative interactions (resonance effects), or by substituent-induced polarization of the p-system in the unsaturated chain (p-polarization effect). Semi-empirical MNDO-PM3 calculations suggest the s-cis conformation of 3-methylene-4-substituted-1,4- -pentadienes as the one with minimal heat of formation.
%K [3]dendralenes
%K unsaturated chain carbon 13C SCS
%K substituent effects
%K reverse 13C SCS effect
%K MNDO-PM3 calculations
%U http://www.shd.org.yu/HtDocs/SHD/Vol68/No2/V68-No2-01.pdf