Carbon-13 Nuclear Magnetic Resonance Spectroscopy. VI. Studies on Carbon-13 Magnetic Resonance Spectra in Aromatic and Heteroaromatic Systems. (2). On the Chemical Shifts of Substituted Pyridine Derivatives

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The carbon-13 chemical shifts of 2-, 3-and 4-substituted pyridine derivatives were examined in relation to those of monosubstituted benzene derivatives and the substituent constants σ_i and σ_π. The results are summarized as follows : 2-Pyridine derivatives δC-R=-20.0+0.62δC-R/PhR δortho=+4.0+1.15δortho/PhR δmeta (C-4)=-8.0-12.5 (σ_i-0.25σ_π) δmeta (C-6)=-21.0+4.5 (σ_i-0.3σ_π) δpara=+6.0+δpara/PhR =+5.8-22.0σ_π 3-Pyridine derivatives δC-R=δC-R/PhR δortho (C-2)=-22.0+0.88δortho/PhR δortho (C-4)=-7.5+δortho/PhR δmeta=+5.0-δmeta/PhR =+4.5-5.0 (σ_i-0.3σ_π) δpara=-20.0+1.10δpara/PhR =-20.0-23.0σ_π 4-Pyridine derivatives δC-R=-10.0+δC-R/PhR δortho=+3.0+1.15δortho/PhR δmeta=-21.6+1.16δmeta/PhR =-21.6+5.0σ_i Simple sum rules were also found to be applicable to symmetrical and unsymmetrical methyl substituted pyridine derivatives.
社団法人日本薬学会の論文
1972-03-25