Inductive and field effects in aromatic substitution. Part VI. The kinetics of hydrogen isotope exchange in quaternary salts of diazacyclophanes and in the related unbridged ions

Abstract

The kinetics of hydrogen isotope exchange between deuteriosulphuric acid and the aromatic protons of diquaternary ions belonging to the series (I; n= 1–3) and (II; n= 2 or 3) have been studied by n.m.r. spectroscopy. A logarithmic plot of the rates of hydrogen isotope exchange against the rates of the corresponding nitration reactions is linear with a slope of 1·5. This relationship supports the view that steric hindrance is not a major factor in determining the deactivation of the bridged ions (II) relative to the open-chain ions (I) for a given value of n. This deactivation is attributed to the greater field effect of the nitrogen poles in the bridged ions.