New Approach for the Elucidation of the Ipso- and α-¹³C Substituent induced Chemical Shifts by the Linear Combination of the Empirical Parameters

Abstract

^<13>C substituent chemical shift (S.C.S.) of the aromatic ipso- and aliphatic α- positions can be expressed by the linear combination of the substituent constants σ_i, σ_π and the standard entropy difference ΔS°. [numerical formula] ΔS°₊ and ΔS°_- denote the standard entropy difference of the electron donating and electron attracting substituent groups.