Determination of reactivity constants of substituted phenyl groups by means of13C NMR

1. 13C chemical shifts have been measured for 3-substituted biphenyls in acetone. 2. On the basis of correlation equations for the benzene ring, the σI and σR∘ constants have been determined for m- and p-substituted phenyl groups. 3. Relationships have been found that can be used to estimate the σ-constants of any m- or p-substituted phenyl group, using known constants of the substituent X.