The 13C NMR spectra of nine ortho‐substituted phenols

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Abstract
The 13C chemical shifts of nine ortho‐substituted phenols have been determined in cyclohexane and in dimethyl sulfoxide. All data were acquired in duplicate upon c.w. and FT instrumentation and both sets of data are presented.The chemical shifts at carbons 1, 2 and 3 are correlated with the parameter Q. Q has been defined as P/Ir3 where P is the polarizability of the adjacent CX bond, I is the first ionization potential of the elements F, Cl, Br, I and H, and r is the CX bond length. Experimental values of Q are available for other substituents. The field and resonance parameters of Swain and Lupton may be combined with Q to form a three part multiple regression correlation which is more exact than that with Q alone and which applies to all carbons in the aromatic ring.The results of this study suggest that only one value of the Q parameter is needed to characterize the behavior of the nitro group in these solvent systems. This conclusion is contrasted with earlier results of the effect of substituents on proton chemical shifts in these systems.