Crossword-Solution: ACRIDINE 8 letters, 2 clues 🏆 scrabble score: 11

The basic red dyes are not very numerous, and comprise Magenta, Saffranine, Acridine Reds, Acridine Scarlets, Rhoduline Reds, Rhodamine and Neutral Beds.

Similarly a CH group may be replaced by a nitrogen atom with the production of compounds of similar stability; thus benzene gives pyridine, naphthalene gives quinoline and isoquinoline; anthracene gives acridine and [alpha] and [beta] anthrapyridines.

The pyridine ring condenses with the benzene ring to form quinoline and isoquinoline; acridine and phenanthridine are dibenzo-pyridines; naphthalene gives rise to [alpha]- and [beta]-naphthoquinolines and the anthrapyridines; anthracene gives anthraquinoline; while two pyridine nuclei connected by an intermediate benzene nucleus give the phenanthrolines.

The quinonoid structure of many coloured compounds has been proved experimentally, as, for example, by Hewitt for the benzene-azo-phenols, and Hantzsch for triaminotriphenyl methane and acridine derivatives; but, at the same time, many substances cannot be so explained.

This tautomerism may be of a twofold nature:--(1) it may involve the mere oscillation of linkages, as in acridine; or (2) it may involve the oscillation of atoms, as in fluorescein.