Analysis of carbon-13 nuclear magnetic resonance shifts in terms of substituent parameters: statistical comparison of dual and single substituent parameter treatments

Abstract

A systematic comparison is made, by using six different scales of substituent parameters, of the -, ß-, and -carbon-13 chemical shifts for the olefinic moiety in four series of styrene derivatives. There is no systematic significant superiority, in general, of a dual substituent parameter (DSP) treatment with respect to the simpler single substituent parameter (MSP) treatment. In the case of the 7-carbons, with the former type of analysis, the inductive effect is found to be more sensitive than the resonance effect to configurational differences.Many studies deal with linear free energy relationships (LEER),1 applied to NMR chemical shifts, especially to 13C values, with a view either to gain some insight into the (1) J. Shorter, "Correlation Analysis in Organic Chemistry", Clarendon Press, Oxford, 1973.

Transmission of substituent effects via molecular lines of force: defense of the DSP method and an illustration of its use in explaining .pi. polarization

“…In other studies25 we have measured extensive series of 13C spectra for structurally related compounds and found that when the data are measured with precision, at low concentration, the DSP correlations for the Cposition of a conjugating side chain are of good quality and consistently show a negative polar substituent effect. We note that 13C spectra for substituted benzylidene malononitriles have been measured by three groups (Laszlo et al, 33 Posner and Hall,7 and Robinson et al49) and that the SCS values derived differ somewhat. We have therefore carefully remeasured 13C SCS values for a series of these compounds.…”

Charge Distribution in 1,1-Dicyano-2-Arylethenes: An Undergraduate Organic Experiment Utilizing the Knoevenagel Condensation and NMR Spectroscopy

“…The results of the NMR interpretations of these Knoevenagel products give students a good insight into the charge distributions in the ethylene side chain (6,7). This information may be used to predict the course of conjugate addition reactions and the rate these compounds may exhibit as dienophiles in Diels-Alder reactions.…”

Asymmetric Conjugate Addition Reactions of Meldrum′s Acid Derived Acceptors Employing Chiral Phosphoramidite Ligands.

“…A chiral ligand 3 was synthesized according to a reported procedure 1) . The title compound (128.6 mg, 0.234 mmol) was obtained as a white foam in 68% yield from 98.5 mg (0.344 mmol) of BINOL and 47.2 mg (0.344 mmol) of (R,R)-Bis-(1-cyclohexyl-ethyl)-amine 2) ; [α] All the substrates except for 1i have been reported in literature (1a, c, d, f, k 3) , 1b, l 4) , 1e, h 5) , 1g 6) , 1j 7) ).…”