Substituent Effects in the Naphthalene Ring System by 19F NMR

Abstract

More than 60 new substituted fluoronaphthalenes, and two new substituted fluorobiphenyls, have been synthesized and their l9F chemical shifts measured. An analysis of the data provided the following conclusions. (1) Geometrical factors, as well as electronic interactions, appear to play a significant role in determining 19F chemical shifts of peri-substituted fluoronaphthalenes. (2) The electronic effect of the trifluoromethyl substituent is a result of both a significant polar and -electron effect. (3) A reexamination of 19F chemical shifts in naphthalene in terms of Taft's DSP equation indicates that the precision of fit is not as good as previously reported. (4) 19F substituent chemical shifts (SCS) from the 6β and 7β orientations can be confidently interpreted in terms of chemical reactivity parameters. Further, these two dispositions appear to have a number of advantages over the meta and para dispositions of fluorobenzene for estimating σ1 and σR0 values of various substituents. © 1976, American Chemical Society. All rights reserved.