Pseudohalogen chemistry .14. Quantitative treatment of the ortho and other substituent effects in the NMR and IR spectra of 2- and 2,4-substituted thiocyanatobenzenes

H-1 and C-13 NMR chemical shifts and IR SCN stretching frequencies for 11 ortho-substituted thiocyanatobenzenes have been measured at high dilution in an inert solvent. Data for delta C(SCN), delta C(ring), delta H(ring and amino) and nu SCN have been correlated with substituent effects using the polar parameter (sigma(F)), the resonance parameter (sigma(R)(0)), Reynolds' short-range, non-electronic parameters (I, O, M) or Holik's second-order resonance parameter, and, as a measure of the ortho effect, the molar refraction parameter (MR) or the steric parameter (E-s). Excellent correlations (r > 0.99) were obtained for data sets involving OMe, Me, F, Cl, Br, I and CN substituents in the ortho position. Ortho NO2 and COMe substituents show deviant behaviour as the SCN group forces each of them to adopt a non-planar conformation. (C) 1997 Elsevier Science B.V.