An N.M.R. Investigation of the Mills-Nixon Effect

Abstract

The ⁴J(H-C^-C-Me) coupling constant, previously established^1-3 as a probe of bond order, was used to examine the bond orders in a series of ortho -bridged compounds: benzocyclopropene , 1,2- dihydrobenzocyclobutene , indan and tetralin . No evidence for sterically induced bond fixation (i.e. the Mills-Nixon⁴ effect) was found, but some evidence for electronic distortion In the corresponding benzylic ketones was observed. The experimental results are in accord with SCF/MO calculations.