Fluorine-19 substituent chemical shifts (SCS)

Abstract

A number of substituted aryl fluorides have been synthesized and their fluorine-19 substituent chemical shifts (scs) have been measured. The comparison of the scs of 1-(m-fluorophenyl)propan-2-one, 1-(p-fluorophenyl)propan-2-one, 7-fluorotetral-2-one, and 6-fluorotetral-2-one confirm Dewars^l-3 conclusions that long-range non-mesomeric effects are transmitted through space and that this polar effect makes a considerable contribution to the overall ¹⁹F scs in aromatic systems. It is also shown that the fluorine substituent chemical shifts of +F+M substituents in 7-substituted 2-fluoronaphthalenes (7β) can be interpreted in terms of a modified FM treatment. The mesomeric-field effect is shown to be important in this disposition (78) of naphthalene.