On Ruhemann's Purple

Abstract

The 1 H 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 1 H nmr spectrum is shown to be due to the presence of a major impurity, identified as hydrindantin. Spectra ( 1 H nmr, 3 C 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.