Isotopic hydrogen exchange in methyl derivatives of five-membered aromatic heterocycles

Abstract

The kinetics of isotopic exchange of the hydrogen atoms of the methyl groups in an alcohol solution of potassium ethoxide were studied for an extensive series of methyl derivatives of azoles and di-, tri-, and tetrazoles. The electronic effect of one or several heteroatoms and substituents on the rate of deuterium exchange of five-membered heterocycles is satisfactorily conveyed by the correlation relationship previously established for a series of substituted toluenes and six-membered heteroaromatic compounds (ρ 25°=7.6). The limitations that exist in a number of cases are discussed in connection with the peculiarities of the electron-density distribution in five- and six-membered heterocycles.