37629-81-5Relevant articles and documents
Replacement Substituent Constants for Simple Heterocycles
Robinson, Charles N.,Wiseman, Leonard J. Jr.,Slater, Carl D.
, p. 4103 - 4112 (2007/10/02)
13C nmr absorptions are reported for the β-vinylic carbon atoms in 15 series of ethylenes bearing heterocyclic substituents.The data are used to establish the best single-parameter substituent constants, ?13, for the various heterocycles as replacements for para-substituted benzenes.Also reported are replacement dual substituent constants, including ?I and the various ?R scales needed in the Taft DSP treatment and those for F and R used in the Swain-Lupton treatment.Values of ?13, F, R, ?I, and ?Ro, respectively, for the various heterocycles as replacements for para-substituted benzenes are as follows: 2-furyl, -1.01 , 0.99, -2.51, 0.65, -0.60; 2-pyrryl, -2.53, 0.52, -5.09, -0.16, -0.62; 2-thienyl, -0.79, 2.49, -3.60, 1.82, -1.08; 3-thienyl, -0.40, 1.04, -1.57, 0.59, -0.39; 2-pyridyl, 0.88, 2.09, -0.24, 1.65, -0.45; 3-pyridyl, 0.60, 0.57, 0.63, 0.35, 0.04; and 4-pyridyl, 1.18, 1.22, 1.09, 0.92, -0.01.The DSP-NLR method of analysis is explored using electron demand parameters, ε, as determined for the vinylic side chains in para-substituted styrenes.
