Association constants for the electron-donor–acceptor complexes of indole and 1-methylindole with 1-(2,4,6-trinitrophenyl)propan-2-one from nuclear magnetic resonance shift measurements. An anomalous scatchard plot

Abstract

Changes (Δ) in the chemical shifts of the protons in the n.m.r. spectrum of the electron acceptor 1-(2,4,6-trinitrophenyl)propan-2-one (A) as a function of added electron donor (D) have been measured for D = indole and D = 1-methylindole, in carbon tetrachloride solution. Although the Scatchard plot (Δ/[D]₀vs.Δ) for the methyl probe in the system involving indole is of an unusual shape, it yields values for parameters on the basis of a double equilibrium involving the formation of DA and D₂A which are consistent with values for the other ¹H probes and also for values of the corresponding 1-methylindole system. The effect of the probable n-merisation of D molecules on the values of the constants for the association of D with A has been estimated.