A comparison of electron impact mass spectrometry of isomeric pyranocoumarins (pyrano[3,2‐<i>c</i>][1]benzopyran‐5‐ones) and pyranochromones (pyrano[2,3‐<i>b</i>][1]benzopyran‐5‐ones)

Abstract

Abstract The mass spectrometric behaviour of two pairs of isomeric 2,2‐dimethylpyrano[3,2‐ c ][1]benzopyran‐5‐ones (pyranocoumarins) and 2,2‐dimethylpyrano[2,3‐ b ][1]benzopyran‐5‐ones (pyranochromones) and four pairs of isomeric 2‐hydroxymethyl‐2‐methylpyrano[3,2‐ c ][1]benzopyran‐5‐ones (pyranocoumarins) and 2‐hydroxymethyl‐2‐methylpyrano[2,3‐ b ][1] benzopyran‐5‐ones (pyranochromones) has been studied in detail with the aid of exact mass measurements, linked scans, collisionally activated decompositions and deuterium labelling experiments. The presence in both series of compounds of the same ions derived by structural interconversion of both molecular ions is emphasized, and structural information on the ions [C 7 H 5 O 2 ] + ( m / z 121), highly characteristic for these classes of compounds, as for 4‐hydroxycoumarins, is reported.