They are both crystalline solids, the former melting when anhydrous at 199-200°, and the latter at 52° C. ' Of the homologues of quinoline, the most important are quinaldine, lepidine, -y-phenylquinoline, and flavoline.
Quinaldine (a-methylquinoline) is present in coal-tar; it may be prepared by condensing aniline with paraldehyde and concentrated hydrochloric acid (0.
Quinaldine may also be obtained by condensing ortho-aminobenzaldehyde with acetone in presence of caustic soda (P. Friedlander, loc. cit.).
Quinaldic acid (quinoline-a-carboxylic acid) is produced when quinaldine is oxidized by chromic acid.