Stabilities of electron donor–acceptor complexes of aromatic hydrocarbons with 1-(2,4,6-trinitrophenyl)propan-2-one in solution from nuclear magnetic resonance shift measurements

Abstract

The change in the chemical shifts of the three singlets in the ¹H n.m.r. spectrum of 1-(2,4,6-trinitrophenyl)propan-2-one (picrylacetone)(A) as a function of the concentration of various added aromatic hydrocarbons, acting as electron donors (D), has been measured under the conditions [D][A]. The results are more consistent with an association in which bimolecular complexes (DA) and termolecular complexes (D₂A) are formed than with a recently proposed model which involves the formation of complexes with only a 1 : 1 stoicheiometry together with ‘additional unspecific shielding’(AUS) of both complexed and uncomplexed acceptor by the donor molecules.