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(2,3-benzopyridine), a heterocyclic compound. Quinoline is a colorless liquid with a characteristic sweetish odor and a boiling point of 238°C.
It is poorly soluble in water and readily soluble in alcohol and ether. It is a weak base and with acids forms salts, such as C9H7N·HCl. With alkyl halides, it forms quinolinium tertiary salts. Quinoline is found in coal tar, from which it is extracted together with isoquinoline. Synthetic quinoline is obtained by the Skraup reaction (seeSKRAUP SYNTHESIS). Quinoline is used as a solvent for sulfur and phosphorus and in the decarboxylation of aromatic acids and other reactions. Many alkaloids, such as quinine and fagarine, and drugs, such as Atophan (cinchophen), Entero-Septol (iodochlorhydroxyquin), chloroquine, and primaquine, are derivatives of quinoline, as are several cyanine dyes and analytical reagents, such as 8-hydroxyquinoline.