Substituent and solvent effects on the 19 F chemical shifts of 3‐ and 4‐XCH 2 ‐substituted fluorobenzenes

Substituent effects on the 19 F chemical shifts of a series of 3‐ and 4‐XCH 2 ‐substituted fluorobenzenes have been studied in five different solvents (dimethyl sulphoxide, acetone, chloroform, carbon tetrachloride and benzene). The results show that in both series substituent effects (other than inductive effects) contribute in at least some cases to the overall shifts, but that these showed little solvent dependence. The meta series showed a proportionately greater solvent dependence than the para series, and this is attributed to the greater importance of ‘through solvent’ direct field effects in the former.