Substituent Effect Study for ¹³C_β SCS in a Meta-Styrene Series. Reynolds Dual Substituent Parameter Model Investigation

Abstract

This article investigates the transmission of the metasubstituent, X, effect to the carbon β (C β ) of 17 different styrenes (X− C 6 H 4 −CHCYZ) using the literature 13 C substituent chemical shift (SCS) of C β . The 13 C SCSs of C β were modeled by Reynolds substituent field σ F and resonance σ R constants. The model is considered a dual substituent parameter model, SCSThe coefficients of determination of the modeled 13 C SCS for the 17 series fall between 0.9878 and 0.9983. The π-polarization concept was used to rationalize the field and resonance effects felt at C β . The ρ F values of the meta-series were all lower than the para-series ρ F values. The substituent field effect transmits to C β from C ipso . The substituent resonance effect transmits from C ipso to C β initially through the π-bond to C ortho and C para , next to the side chain, and then the generated charge will induce the vinyl group via π-polarization. The ρ F felt at C β was almost double the ρ R when compared with the short distance between C meta and C β , as opposed to C ortho and C para . Stabilization of the π-polarization of the vinyl group will increase, with the field and resonance effects felt at C β and vice versa.