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Paper | Special issue | Vol 37, No. 3, 1994, pp.1495-1501
Published online, 1st January, 1970
DOI: 10.3987/COM-93-S62
Effect of Substituteents on the 1H and 13C NMR Chemical Shift of trans-Pyridineacrylic and Substituted trans-Cinnamic Acids

Bratislav Jovanovic,* Milica Misic-Vukovic, Sasa Drmanic, and János Csanádi

*Facluty of Technology and Metallurgy, University of Belgrade, 11000 Belgrade, Yugoslavia

Abstract

The principles of linear free energy relationships were applied to the 1H nmr and 13C nmr chemical shifts induced by suhstituents in three isomeric trans-pyridineacrylic and substituted trans-cinnamic acids. The data for the carboxy proton chemical shift correlated well with the simple Hammett equation. Taft’s dual substituent parameter equation was used for the interpretation of the balance of the inductive and resonance effects through the ethylenic bond for the Cα and Cβ 13C nmr shift. Using the nuclear Overhauser method, the conformation of the carboxylic group in 2-pyridineacrylic acid was determined, and its unexpected behaviour in both 1H nmr chemical shifts and in the previously studied reaction with diazodiphenylmethane was interpreted by the increased electron density in the Π-electronic system favoured by the orbital symmetry of the part of the acid molecule.