Phenylpyridines preparation from carbon

The actual location of the —COOH group at carbon 3 was established by Skraup and CobenzD by physical and chemical criteria. Through a series of steps 3 phenylpyridine is prepared from j >-naphthylamine and glycerine, and upon oxidation it yields nicotinic acid. Skraup and Vortmanni, also prepared nicotinic acid from synthetic dipyridyl of known w-structure. The three position isomers have very different melting points picolinic acid (0-, or 1,2) around 136° nicotinic acid m- or 1,3-) around 236° and isonicotinic acidi p- or 1,4-) iiround 319°. 

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