It condenses with aceto-acetic ester, in the presence of sulphuric acid, to 0-methyl coumarin (H.
A-pyrone condenses with the benzene ring to form coumarin and isocoumarin; benzo-'y-pyrone constitutes the nucleus of several vegetable colouring matters (chrysin, fisetin, quercetin, &c., which are derivatives of flavone or phenyl benzo-y-pyrone); dibenzo--ypyrone is known as xanthone; related to this substance are fluorane (and fluorescein), fluorone, fluorime, pyronine, &c. The pyridine ring condenses with the benzene ring to form quinoline and isoquinoline; acridine and phenanthridine are dibenzo-pyridines; naphthalene gives rise to a-and /3-naphthoquinolines and the anthrapyridines; anthracene gives anthraquinoline; while two pyridine nuclei connected by an intermediate benzene nucleus give the phenanthrolines.
Anthoxanthum odoratum, the sweet vernal grass of our flora, owes its scent to the presence of coumarin, which is also present in the closely allied genus Hierochloe (fig.
These researches incidentally solved the constitution of coumarin, the odoriferous principle of woodruff.
This was followed by the production of heliotropin, coumarin and vanillin, and later on by the artificial preparation of ionone, the most characteristic constituent of the violet scent.