On Ruhemann's Purple

Abstract

The 1H nmr spectrum previously reported for Ruhemann's Purple is shown to be inconsistent with the accepted structure of this material. The discrepancy with the reported 1H nmr spectrum is shown to be due to the presence of a major impurity, identified as hydrindantin. Spectra (1H nmr, 3C nmr, ir, uv–visible) of Ruhemann's Purple, its protonated analogue DYDA, and other ninhydrin relatives are reported, and structural conclusions are based on these spectral data.